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![Paul E. McKenney](/assets/img/avatar_default.png)
doctorture.2013.01.11a: Changes to rcutorture and to RCU documentation. fixes.2013.01.26a: Miscellaneous fixes. tagcb.2013.01.24a: Tag RCU callbacks with grace-period number to simplify callback advancement. tiny.2013.01.29b: Enhancements to uniprocessor handling in tiny RCU.
3186 lines
98 KiB
C
3186 lines
98 KiB
C
/*
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* Read-Copy Update mechanism for mutual exclusion
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
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*
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* Copyright IBM Corporation, 2008
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*
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* Authors: Dipankar Sarma <dipankar@in.ibm.com>
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* Manfred Spraul <manfred@colorfullife.com>
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* Paul E. McKenney <paulmck@linux.vnet.ibm.com> Hierarchical version
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*
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* Based on the original work by Paul McKenney <paulmck@us.ibm.com>
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* and inputs from Rusty Russell, Andrea Arcangeli and Andi Kleen.
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*
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* For detailed explanation of Read-Copy Update mechanism see -
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* Documentation/RCU
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*/
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#include <linux/types.h>
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#include <linux/kernel.h>
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#include <linux/init.h>
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#include <linux/spinlock.h>
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#include <linux/smp.h>
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#include <linux/rcupdate.h>
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#include <linux/interrupt.h>
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#include <linux/sched.h>
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#include <linux/nmi.h>
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#include <linux/atomic.h>
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#include <linux/bitops.h>
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#include <linux/export.h>
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#include <linux/completion.h>
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#include <linux/moduleparam.h>
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#include <linux/percpu.h>
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#include <linux/notifier.h>
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#include <linux/cpu.h>
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#include <linux/mutex.h>
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#include <linux/time.h>
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#include <linux/kernel_stat.h>
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#include <linux/wait.h>
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#include <linux/kthread.h>
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#include <linux/prefetch.h>
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#include <linux/delay.h>
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#include <linux/stop_machine.h>
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#include <linux/random.h>
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#include "rcutree.h"
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#include <trace/events/rcu.h>
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#include "rcu.h"
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/* Data structures. */
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static struct lock_class_key rcu_node_class[RCU_NUM_LVLS];
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static struct lock_class_key rcu_fqs_class[RCU_NUM_LVLS];
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#define RCU_STATE_INITIALIZER(sname, cr) { \
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.level = { &sname##_state.node[0] }, \
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.call = cr, \
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.fqs_state = RCU_GP_IDLE, \
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.gpnum = 0UL - 300UL, \
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.completed = 0UL - 300UL, \
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.orphan_lock = __RAW_SPIN_LOCK_UNLOCKED(&sname##_state.orphan_lock), \
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.orphan_nxttail = &sname##_state.orphan_nxtlist, \
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.orphan_donetail = &sname##_state.orphan_donelist, \
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.barrier_mutex = __MUTEX_INITIALIZER(sname##_state.barrier_mutex), \
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.onoff_mutex = __MUTEX_INITIALIZER(sname##_state.onoff_mutex), \
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.name = #sname, \
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}
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struct rcu_state rcu_sched_state =
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RCU_STATE_INITIALIZER(rcu_sched, call_rcu_sched);
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DEFINE_PER_CPU(struct rcu_data, rcu_sched_data);
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struct rcu_state rcu_bh_state = RCU_STATE_INITIALIZER(rcu_bh, call_rcu_bh);
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DEFINE_PER_CPU(struct rcu_data, rcu_bh_data);
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static struct rcu_state *rcu_state;
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LIST_HEAD(rcu_struct_flavors);
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/* Increase (but not decrease) the CONFIG_RCU_FANOUT_LEAF at boot time. */
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static int rcu_fanout_leaf = CONFIG_RCU_FANOUT_LEAF;
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module_param(rcu_fanout_leaf, int, 0444);
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int rcu_num_lvls __read_mostly = RCU_NUM_LVLS;
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static int num_rcu_lvl[] = { /* Number of rcu_nodes at specified level. */
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NUM_RCU_LVL_0,
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NUM_RCU_LVL_1,
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NUM_RCU_LVL_2,
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NUM_RCU_LVL_3,
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NUM_RCU_LVL_4,
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};
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int rcu_num_nodes __read_mostly = NUM_RCU_NODES; /* Total # rcu_nodes in use. */
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/*
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* The rcu_scheduler_active variable transitions from zero to one just
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* before the first task is spawned. So when this variable is zero, RCU
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* can assume that there is but one task, allowing RCU to (for example)
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* optimize synchronize_sched() to a simple barrier(). When this variable
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* is one, RCU must actually do all the hard work required to detect real
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* grace periods. This variable is also used to suppress boot-time false
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* positives from lockdep-RCU error checking.
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*/
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int rcu_scheduler_active __read_mostly;
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EXPORT_SYMBOL_GPL(rcu_scheduler_active);
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/*
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* The rcu_scheduler_fully_active variable transitions from zero to one
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* during the early_initcall() processing, which is after the scheduler
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* is capable of creating new tasks. So RCU processing (for example,
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* creating tasks for RCU priority boosting) must be delayed until after
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* rcu_scheduler_fully_active transitions from zero to one. We also
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* currently delay invocation of any RCU callbacks until after this point.
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*
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* It might later prove better for people registering RCU callbacks during
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* early boot to take responsibility for these callbacks, but one step at
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* a time.
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*/
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static int rcu_scheduler_fully_active __read_mostly;
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#ifdef CONFIG_RCU_BOOST
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/*
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* Control variables for per-CPU and per-rcu_node kthreads. These
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* handle all flavors of RCU.
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*/
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static DEFINE_PER_CPU(struct task_struct *, rcu_cpu_kthread_task);
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DEFINE_PER_CPU(unsigned int, rcu_cpu_kthread_status);
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DEFINE_PER_CPU(unsigned int, rcu_cpu_kthread_loops);
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DEFINE_PER_CPU(char, rcu_cpu_has_work);
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#endif /* #ifdef CONFIG_RCU_BOOST */
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static void rcu_boost_kthread_setaffinity(struct rcu_node *rnp, int outgoingcpu);
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static void invoke_rcu_core(void);
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static void invoke_rcu_callbacks(struct rcu_state *rsp, struct rcu_data *rdp);
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/*
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* Track the rcutorture test sequence number and the update version
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* number within a given test. The rcutorture_testseq is incremented
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* on every rcutorture module load and unload, so has an odd value
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* when a test is running. The rcutorture_vernum is set to zero
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* when rcutorture starts and is incremented on each rcutorture update.
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* These variables enable correlating rcutorture output with the
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* RCU tracing information.
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*/
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unsigned long rcutorture_testseq;
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unsigned long rcutorture_vernum;
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/*
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* Return true if an RCU grace period is in progress. The ACCESS_ONCE()s
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* permit this function to be invoked without holding the root rcu_node
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* structure's ->lock, but of course results can be subject to change.
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*/
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static int rcu_gp_in_progress(struct rcu_state *rsp)
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{
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return ACCESS_ONCE(rsp->completed) != ACCESS_ONCE(rsp->gpnum);
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}
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/*
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* Note a quiescent state. Because we do not need to know
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* how many quiescent states passed, just if there was at least
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* one since the start of the grace period, this just sets a flag.
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* The caller must have disabled preemption.
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*/
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void rcu_sched_qs(int cpu)
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{
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struct rcu_data *rdp = &per_cpu(rcu_sched_data, cpu);
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if (rdp->passed_quiesce == 0)
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trace_rcu_grace_period("rcu_sched", rdp->gpnum, "cpuqs");
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rdp->passed_quiesce = 1;
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}
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void rcu_bh_qs(int cpu)
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{
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struct rcu_data *rdp = &per_cpu(rcu_bh_data, cpu);
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if (rdp->passed_quiesce == 0)
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trace_rcu_grace_period("rcu_bh", rdp->gpnum, "cpuqs");
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rdp->passed_quiesce = 1;
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}
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/*
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* Note a context switch. This is a quiescent state for RCU-sched,
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* and requires special handling for preemptible RCU.
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* The caller must have disabled preemption.
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*/
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void rcu_note_context_switch(int cpu)
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{
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trace_rcu_utilization("Start context switch");
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rcu_sched_qs(cpu);
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rcu_preempt_note_context_switch(cpu);
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trace_rcu_utilization("End context switch");
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}
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EXPORT_SYMBOL_GPL(rcu_note_context_switch);
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DEFINE_PER_CPU(struct rcu_dynticks, rcu_dynticks) = {
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.dynticks_nesting = DYNTICK_TASK_EXIT_IDLE,
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.dynticks = ATOMIC_INIT(1),
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};
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static long blimit = 10; /* Maximum callbacks per rcu_do_batch. */
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static long qhimark = 10000; /* If this many pending, ignore blimit. */
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static long qlowmark = 100; /* Once only this many pending, use blimit. */
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module_param(blimit, long, 0444);
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module_param(qhimark, long, 0444);
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module_param(qlowmark, long, 0444);
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static ulong jiffies_till_first_fqs = RCU_JIFFIES_TILL_FORCE_QS;
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static ulong jiffies_till_next_fqs = RCU_JIFFIES_TILL_FORCE_QS;
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module_param(jiffies_till_first_fqs, ulong, 0644);
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module_param(jiffies_till_next_fqs, ulong, 0644);
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static void force_qs_rnp(struct rcu_state *rsp, int (*f)(struct rcu_data *));
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static void force_quiescent_state(struct rcu_state *rsp);
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static int rcu_pending(int cpu);
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/*
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* Return the number of RCU-sched batches processed thus far for debug & stats.
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*/
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long rcu_batches_completed_sched(void)
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{
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return rcu_sched_state.completed;
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}
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EXPORT_SYMBOL_GPL(rcu_batches_completed_sched);
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/*
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* Return the number of RCU BH batches processed thus far for debug & stats.
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*/
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long rcu_batches_completed_bh(void)
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{
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return rcu_bh_state.completed;
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}
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EXPORT_SYMBOL_GPL(rcu_batches_completed_bh);
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/*
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* Force a quiescent state for RCU BH.
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*/
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void rcu_bh_force_quiescent_state(void)
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{
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force_quiescent_state(&rcu_bh_state);
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}
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EXPORT_SYMBOL_GPL(rcu_bh_force_quiescent_state);
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/*
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* Record the number of times rcutorture tests have been initiated and
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* terminated. This information allows the debugfs tracing stats to be
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* correlated to the rcutorture messages, even when the rcutorture module
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* is being repeatedly loaded and unloaded. In other words, we cannot
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* store this state in rcutorture itself.
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*/
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void rcutorture_record_test_transition(void)
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{
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rcutorture_testseq++;
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rcutorture_vernum = 0;
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}
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EXPORT_SYMBOL_GPL(rcutorture_record_test_transition);
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/*
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* Record the number of writer passes through the current rcutorture test.
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* This is also used to correlate debugfs tracing stats with the rcutorture
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* messages.
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*/
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void rcutorture_record_progress(unsigned long vernum)
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{
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rcutorture_vernum++;
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}
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EXPORT_SYMBOL_GPL(rcutorture_record_progress);
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/*
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* Force a quiescent state for RCU-sched.
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*/
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void rcu_sched_force_quiescent_state(void)
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{
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force_quiescent_state(&rcu_sched_state);
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}
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EXPORT_SYMBOL_GPL(rcu_sched_force_quiescent_state);
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/*
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* Does the CPU have callbacks ready to be invoked?
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*/
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static int
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cpu_has_callbacks_ready_to_invoke(struct rcu_data *rdp)
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{
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return &rdp->nxtlist != rdp->nxttail[RCU_DONE_TAIL] &&
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rdp->nxttail[RCU_DONE_TAIL] != NULL;
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}
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/*
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* Does the current CPU require a not-yet-started grace period?
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* The caller must have disabled interrupts to prevent races with
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* normal callback registry.
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*/
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static int
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cpu_needs_another_gp(struct rcu_state *rsp, struct rcu_data *rdp)
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{
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int i;
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if (rcu_gp_in_progress(rsp))
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return 0; /* No, a grace period is already in progress. */
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if (!rdp->nxttail[RCU_NEXT_TAIL])
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return 0; /* No, this is a no-CBs (or offline) CPU. */
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if (*rdp->nxttail[RCU_NEXT_READY_TAIL])
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return 1; /* Yes, this CPU has newly registered callbacks. */
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for (i = RCU_WAIT_TAIL; i < RCU_NEXT_TAIL; i++)
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if (rdp->nxttail[i - 1] != rdp->nxttail[i] &&
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ULONG_CMP_LT(ACCESS_ONCE(rsp->completed),
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rdp->nxtcompleted[i]))
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return 1; /* Yes, CBs for future grace period. */
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return 0; /* No grace period needed. */
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}
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/*
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* Return the root node of the specified rcu_state structure.
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*/
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static struct rcu_node *rcu_get_root(struct rcu_state *rsp)
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{
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return &rsp->node[0];
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}
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/*
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* rcu_eqs_enter_common - current CPU is moving towards extended quiescent state
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*
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* If the new value of the ->dynticks_nesting counter now is zero,
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* we really have entered idle, and must do the appropriate accounting.
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* The caller must have disabled interrupts.
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*/
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static void rcu_eqs_enter_common(struct rcu_dynticks *rdtp, long long oldval,
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bool user)
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{
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trace_rcu_dyntick("Start", oldval, rdtp->dynticks_nesting);
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if (!user && !is_idle_task(current)) {
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struct task_struct *idle = idle_task(smp_processor_id());
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trace_rcu_dyntick("Error on entry: not idle task", oldval, 0);
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ftrace_dump(DUMP_ORIG);
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WARN_ONCE(1, "Current pid: %d comm: %s / Idle pid: %d comm: %s",
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current->pid, current->comm,
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idle->pid, idle->comm); /* must be idle task! */
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}
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rcu_prepare_for_idle(smp_processor_id());
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/* CPUs seeing atomic_inc() must see prior RCU read-side crit sects */
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smp_mb__before_atomic_inc(); /* See above. */
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atomic_inc(&rdtp->dynticks);
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smp_mb__after_atomic_inc(); /* Force ordering with next sojourn. */
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WARN_ON_ONCE(atomic_read(&rdtp->dynticks) & 0x1);
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/*
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* It is illegal to enter an extended quiescent state while
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* in an RCU read-side critical section.
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*/
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rcu_lockdep_assert(!lock_is_held(&rcu_lock_map),
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"Illegal idle entry in RCU read-side critical section.");
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rcu_lockdep_assert(!lock_is_held(&rcu_bh_lock_map),
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"Illegal idle entry in RCU-bh read-side critical section.");
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rcu_lockdep_assert(!lock_is_held(&rcu_sched_lock_map),
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"Illegal idle entry in RCU-sched read-side critical section.");
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}
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/*
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* Enter an RCU extended quiescent state, which can be either the
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* idle loop or adaptive-tickless usermode execution.
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*/
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static void rcu_eqs_enter(bool user)
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{
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long long oldval;
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struct rcu_dynticks *rdtp;
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rdtp = &__get_cpu_var(rcu_dynticks);
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oldval = rdtp->dynticks_nesting;
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WARN_ON_ONCE((oldval & DYNTICK_TASK_NEST_MASK) == 0);
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if ((oldval & DYNTICK_TASK_NEST_MASK) == DYNTICK_TASK_NEST_VALUE)
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rdtp->dynticks_nesting = 0;
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else
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rdtp->dynticks_nesting -= DYNTICK_TASK_NEST_VALUE;
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rcu_eqs_enter_common(rdtp, oldval, user);
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}
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/**
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* rcu_idle_enter - inform RCU that current CPU is entering idle
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*
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* Enter idle mode, in other words, -leave- the mode in which RCU
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* read-side critical sections can occur. (Though RCU read-side
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* critical sections can occur in irq handlers in idle, a possibility
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* handled by irq_enter() and irq_exit().)
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*
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* We crowbar the ->dynticks_nesting field to zero to allow for
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* the possibility of usermode upcalls having messed up our count
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* of interrupt nesting level during the prior busy period.
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*/
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void rcu_idle_enter(void)
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{
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unsigned long flags;
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local_irq_save(flags);
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rcu_eqs_enter(false);
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local_irq_restore(flags);
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}
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EXPORT_SYMBOL_GPL(rcu_idle_enter);
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#ifdef CONFIG_RCU_USER_QS
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/**
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* rcu_user_enter - inform RCU that we are resuming userspace.
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*
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* Enter RCU idle mode right before resuming userspace. No use of RCU
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* is permitted between this call and rcu_user_exit(). This way the
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* CPU doesn't need to maintain the tick for RCU maintenance purposes
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* when the CPU runs in userspace.
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*/
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void rcu_user_enter(void)
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{
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rcu_eqs_enter(1);
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}
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/**
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* rcu_user_enter_after_irq - inform RCU that we are going to resume userspace
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* after the current irq returns.
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*
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* This is similar to rcu_user_enter() but in the context of a non-nesting
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* irq. After this call, RCU enters into idle mode when the interrupt
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* returns.
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*/
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void rcu_user_enter_after_irq(void)
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{
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unsigned long flags;
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struct rcu_dynticks *rdtp;
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local_irq_save(flags);
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rdtp = &__get_cpu_var(rcu_dynticks);
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/* Ensure this irq is interrupting a non-idle RCU state. */
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WARN_ON_ONCE(!(rdtp->dynticks_nesting & DYNTICK_TASK_MASK));
|
|
rdtp->dynticks_nesting = 1;
|
|
local_irq_restore(flags);
|
|
}
|
|
#endif /* CONFIG_RCU_USER_QS */
|
|
|
|
/**
|
|
* rcu_irq_exit - inform RCU that current CPU is exiting irq towards idle
|
|
*
|
|
* Exit from an interrupt handler, which might possibly result in entering
|
|
* idle mode, in other words, leaving the mode in which read-side critical
|
|
* sections can occur.
|
|
*
|
|
* This code assumes that the idle loop never does anything that might
|
|
* result in unbalanced calls to irq_enter() and irq_exit(). If your
|
|
* architecture violates this assumption, RCU will give you what you
|
|
* deserve, good and hard. But very infrequently and irreproducibly.
|
|
*
|
|
* Use things like work queues to work around this limitation.
|
|
*
|
|
* You have been warned.
|
|
*/
|
|
void rcu_irq_exit(void)
|
|
{
|
|
unsigned long flags;
|
|
long long oldval;
|
|
struct rcu_dynticks *rdtp;
|
|
|
|
local_irq_save(flags);
|
|
rdtp = &__get_cpu_var(rcu_dynticks);
|
|
oldval = rdtp->dynticks_nesting;
|
|
rdtp->dynticks_nesting--;
|
|
WARN_ON_ONCE(rdtp->dynticks_nesting < 0);
|
|
if (rdtp->dynticks_nesting)
|
|
trace_rcu_dyntick("--=", oldval, rdtp->dynticks_nesting);
|
|
else
|
|
rcu_eqs_enter_common(rdtp, oldval, true);
|
|
local_irq_restore(flags);
|
|
}
|
|
|
|
/*
|
|
* rcu_eqs_exit_common - current CPU moving away from extended quiescent state
|
|
*
|
|
* If the new value of the ->dynticks_nesting counter was previously zero,
|
|
* we really have exited idle, and must do the appropriate accounting.
|
|
* The caller must have disabled interrupts.
|
|
*/
|
|
static void rcu_eqs_exit_common(struct rcu_dynticks *rdtp, long long oldval,
|
|
int user)
|
|
{
|
|
smp_mb__before_atomic_inc(); /* Force ordering w/previous sojourn. */
|
|
atomic_inc(&rdtp->dynticks);
|
|
/* CPUs seeing atomic_inc() must see later RCU read-side crit sects */
|
|
smp_mb__after_atomic_inc(); /* See above. */
|
|
WARN_ON_ONCE(!(atomic_read(&rdtp->dynticks) & 0x1));
|
|
rcu_cleanup_after_idle(smp_processor_id());
|
|
trace_rcu_dyntick("End", oldval, rdtp->dynticks_nesting);
|
|
if (!user && !is_idle_task(current)) {
|
|
struct task_struct *idle = idle_task(smp_processor_id());
|
|
|
|
trace_rcu_dyntick("Error on exit: not idle task",
|
|
oldval, rdtp->dynticks_nesting);
|
|
ftrace_dump(DUMP_ORIG);
|
|
WARN_ONCE(1, "Current pid: %d comm: %s / Idle pid: %d comm: %s",
|
|
current->pid, current->comm,
|
|
idle->pid, idle->comm); /* must be idle task! */
|
|
}
|
|
}
|
|
|
|
/*
|
|
* Exit an RCU extended quiescent state, which can be either the
|
|
* idle loop or adaptive-tickless usermode execution.
|
|
*/
|
|
static void rcu_eqs_exit(bool user)
|
|
{
|
|
struct rcu_dynticks *rdtp;
|
|
long long oldval;
|
|
|
|
rdtp = &__get_cpu_var(rcu_dynticks);
|
|
oldval = rdtp->dynticks_nesting;
|
|
WARN_ON_ONCE(oldval < 0);
|
|
if (oldval & DYNTICK_TASK_NEST_MASK)
|
|
rdtp->dynticks_nesting += DYNTICK_TASK_NEST_VALUE;
|
|
else
|
|
rdtp->dynticks_nesting = DYNTICK_TASK_EXIT_IDLE;
|
|
rcu_eqs_exit_common(rdtp, oldval, user);
|
|
}
|
|
|
|
/**
|
|
* rcu_idle_exit - inform RCU that current CPU is leaving idle
|
|
*
|
|
* Exit idle mode, in other words, -enter- the mode in which RCU
|
|
* read-side critical sections can occur.
|
|
*
|
|
* We crowbar the ->dynticks_nesting field to DYNTICK_TASK_NEST to
|
|
* allow for the possibility of usermode upcalls messing up our count
|
|
* of interrupt nesting level during the busy period that is just
|
|
* now starting.
|
|
*/
|
|
void rcu_idle_exit(void)
|
|
{
|
|
unsigned long flags;
|
|
|
|
local_irq_save(flags);
|
|
rcu_eqs_exit(false);
|
|
local_irq_restore(flags);
|
|
}
|
|
EXPORT_SYMBOL_GPL(rcu_idle_exit);
|
|
|
|
#ifdef CONFIG_RCU_USER_QS
|
|
/**
|
|
* rcu_user_exit - inform RCU that we are exiting userspace.
|
|
*
|
|
* Exit RCU idle mode while entering the kernel because it can
|
|
* run a RCU read side critical section anytime.
|
|
*/
|
|
void rcu_user_exit(void)
|
|
{
|
|
rcu_eqs_exit(1);
|
|
}
|
|
|
|
/**
|
|
* rcu_user_exit_after_irq - inform RCU that we won't resume to userspace
|
|
* idle mode after the current non-nesting irq returns.
|
|
*
|
|
* This is similar to rcu_user_exit() but in the context of an irq.
|
|
* This is called when the irq has interrupted a userspace RCU idle mode
|
|
* context. When the current non-nesting interrupt returns after this call,
|
|
* the CPU won't restore the RCU idle mode.
|
|
*/
|
|
void rcu_user_exit_after_irq(void)
|
|
{
|
|
unsigned long flags;
|
|
struct rcu_dynticks *rdtp;
|
|
|
|
local_irq_save(flags);
|
|
rdtp = &__get_cpu_var(rcu_dynticks);
|
|
/* Ensure we are interrupting an RCU idle mode. */
|
|
WARN_ON_ONCE(rdtp->dynticks_nesting & DYNTICK_TASK_NEST_MASK);
|
|
rdtp->dynticks_nesting += DYNTICK_TASK_EXIT_IDLE;
|
|
local_irq_restore(flags);
|
|
}
|
|
#endif /* CONFIG_RCU_USER_QS */
|
|
|
|
/**
|
|
* rcu_irq_enter - inform RCU that current CPU is entering irq away from idle
|
|
*
|
|
* Enter an interrupt handler, which might possibly result in exiting
|
|
* idle mode, in other words, entering the mode in which read-side critical
|
|
* sections can occur.
|
|
*
|
|
* Note that the Linux kernel is fully capable of entering an interrupt
|
|
* handler that it never exits, for example when doing upcalls to
|
|
* user mode! This code assumes that the idle loop never does upcalls to
|
|
* user mode. If your architecture does do upcalls from the idle loop (or
|
|
* does anything else that results in unbalanced calls to the irq_enter()
|
|
* and irq_exit() functions), RCU will give you what you deserve, good
|
|
* and hard. But very infrequently and irreproducibly.
|
|
*
|
|
* Use things like work queues to work around this limitation.
|
|
*
|
|
* You have been warned.
|
|
*/
|
|
void rcu_irq_enter(void)
|
|
{
|
|
unsigned long flags;
|
|
struct rcu_dynticks *rdtp;
|
|
long long oldval;
|
|
|
|
local_irq_save(flags);
|
|
rdtp = &__get_cpu_var(rcu_dynticks);
|
|
oldval = rdtp->dynticks_nesting;
|
|
rdtp->dynticks_nesting++;
|
|
WARN_ON_ONCE(rdtp->dynticks_nesting == 0);
|
|
if (oldval)
|
|
trace_rcu_dyntick("++=", oldval, rdtp->dynticks_nesting);
|
|
else
|
|
rcu_eqs_exit_common(rdtp, oldval, true);
|
|
local_irq_restore(flags);
|
|
}
|
|
|
|
/**
|
|
* rcu_nmi_enter - inform RCU of entry to NMI context
|
|
*
|
|
* If the CPU was idle with dynamic ticks active, and there is no
|
|
* irq handler running, this updates rdtp->dynticks_nmi to let the
|
|
* RCU grace-period handling know that the CPU is active.
|
|
*/
|
|
void rcu_nmi_enter(void)
|
|
{
|
|
struct rcu_dynticks *rdtp = &__get_cpu_var(rcu_dynticks);
|
|
|
|
if (rdtp->dynticks_nmi_nesting == 0 &&
|
|
(atomic_read(&rdtp->dynticks) & 0x1))
|
|
return;
|
|
rdtp->dynticks_nmi_nesting++;
|
|
smp_mb__before_atomic_inc(); /* Force delay from prior write. */
|
|
atomic_inc(&rdtp->dynticks);
|
|
/* CPUs seeing atomic_inc() must see later RCU read-side crit sects */
|
|
smp_mb__after_atomic_inc(); /* See above. */
|
|
WARN_ON_ONCE(!(atomic_read(&rdtp->dynticks) & 0x1));
|
|
}
|
|
|
|
/**
|
|
* rcu_nmi_exit - inform RCU of exit from NMI context
|
|
*
|
|
* If the CPU was idle with dynamic ticks active, and there is no
|
|
* irq handler running, this updates rdtp->dynticks_nmi to let the
|
|
* RCU grace-period handling know that the CPU is no longer active.
|
|
*/
|
|
void rcu_nmi_exit(void)
|
|
{
|
|
struct rcu_dynticks *rdtp = &__get_cpu_var(rcu_dynticks);
|
|
|
|
if (rdtp->dynticks_nmi_nesting == 0 ||
|
|
--rdtp->dynticks_nmi_nesting != 0)
|
|
return;
|
|
/* CPUs seeing atomic_inc() must see prior RCU read-side crit sects */
|
|
smp_mb__before_atomic_inc(); /* See above. */
|
|
atomic_inc(&rdtp->dynticks);
|
|
smp_mb__after_atomic_inc(); /* Force delay to next write. */
|
|
WARN_ON_ONCE(atomic_read(&rdtp->dynticks) & 0x1);
|
|
}
|
|
|
|
/**
|
|
* rcu_is_cpu_idle - see if RCU thinks that the current CPU is idle
|
|
*
|
|
* If the current CPU is in its idle loop and is neither in an interrupt
|
|
* or NMI handler, return true.
|
|
*/
|
|
int rcu_is_cpu_idle(void)
|
|
{
|
|
int ret;
|
|
|
|
preempt_disable();
|
|
ret = (atomic_read(&__get_cpu_var(rcu_dynticks).dynticks) & 0x1) == 0;
|
|
preempt_enable();
|
|
return ret;
|
|
}
|
|
EXPORT_SYMBOL(rcu_is_cpu_idle);
|
|
|
|
#if defined(CONFIG_PROVE_RCU) && defined(CONFIG_HOTPLUG_CPU)
|
|
|
|
/*
|
|
* Is the current CPU online? Disable preemption to avoid false positives
|
|
* that could otherwise happen due to the current CPU number being sampled,
|
|
* this task being preempted, its old CPU being taken offline, resuming
|
|
* on some other CPU, then determining that its old CPU is now offline.
|
|
* It is OK to use RCU on an offline processor during initial boot, hence
|
|
* the check for rcu_scheduler_fully_active. Note also that it is OK
|
|
* for a CPU coming online to use RCU for one jiffy prior to marking itself
|
|
* online in the cpu_online_mask. Similarly, it is OK for a CPU going
|
|
* offline to continue to use RCU for one jiffy after marking itself
|
|
* offline in the cpu_online_mask. This leniency is necessary given the
|
|
* non-atomic nature of the online and offline processing, for example,
|
|
* the fact that a CPU enters the scheduler after completing the CPU_DYING
|
|
* notifiers.
|
|
*
|
|
* This is also why RCU internally marks CPUs online during the
|
|
* CPU_UP_PREPARE phase and offline during the CPU_DEAD phase.
|
|
*
|
|
* Disable checking if in an NMI handler because we cannot safely report
|
|
* errors from NMI handlers anyway.
|
|
*/
|
|
bool rcu_lockdep_current_cpu_online(void)
|
|
{
|
|
struct rcu_data *rdp;
|
|
struct rcu_node *rnp;
|
|
bool ret;
|
|
|
|
if (in_nmi())
|
|
return 1;
|
|
preempt_disable();
|
|
rdp = &__get_cpu_var(rcu_sched_data);
|
|
rnp = rdp->mynode;
|
|
ret = (rdp->grpmask & rnp->qsmaskinit) ||
|
|
!rcu_scheduler_fully_active;
|
|
preempt_enable();
|
|
return ret;
|
|
}
|
|
EXPORT_SYMBOL_GPL(rcu_lockdep_current_cpu_online);
|
|
|
|
#endif /* #if defined(CONFIG_PROVE_RCU) && defined(CONFIG_HOTPLUG_CPU) */
|
|
|
|
/**
|
|
* rcu_is_cpu_rrupt_from_idle - see if idle or immediately interrupted from idle
|
|
*
|
|
* If the current CPU is idle or running at a first-level (not nested)
|
|
* interrupt from idle, return true. The caller must have at least
|
|
* disabled preemption.
|
|
*/
|
|
static int rcu_is_cpu_rrupt_from_idle(void)
|
|
{
|
|
return __get_cpu_var(rcu_dynticks).dynticks_nesting <= 1;
|
|
}
|
|
|
|
/*
|
|
* Snapshot the specified CPU's dynticks counter so that we can later
|
|
* credit them with an implicit quiescent state. Return 1 if this CPU
|
|
* is in dynticks idle mode, which is an extended quiescent state.
|
|
*/
|
|
static int dyntick_save_progress_counter(struct rcu_data *rdp)
|
|
{
|
|
rdp->dynticks_snap = atomic_add_return(0, &rdp->dynticks->dynticks);
|
|
return (rdp->dynticks_snap & 0x1) == 0;
|
|
}
|
|
|
|
/*
|
|
* Return true if the specified CPU has passed through a quiescent
|
|
* state by virtue of being in or having passed through an dynticks
|
|
* idle state since the last call to dyntick_save_progress_counter()
|
|
* for this same CPU, or by virtue of having been offline.
|
|
*/
|
|
static int rcu_implicit_dynticks_qs(struct rcu_data *rdp)
|
|
{
|
|
unsigned int curr;
|
|
unsigned int snap;
|
|
|
|
curr = (unsigned int)atomic_add_return(0, &rdp->dynticks->dynticks);
|
|
snap = (unsigned int)rdp->dynticks_snap;
|
|
|
|
/*
|
|
* If the CPU passed through or entered a dynticks idle phase with
|
|
* no active irq/NMI handlers, then we can safely pretend that the CPU
|
|
* already acknowledged the request to pass through a quiescent
|
|
* state. Either way, that CPU cannot possibly be in an RCU
|
|
* read-side critical section that started before the beginning
|
|
* of the current RCU grace period.
|
|
*/
|
|
if ((curr & 0x1) == 0 || UINT_CMP_GE(curr, snap + 2)) {
|
|
trace_rcu_fqs(rdp->rsp->name, rdp->gpnum, rdp->cpu, "dti");
|
|
rdp->dynticks_fqs++;
|
|
return 1;
|
|
}
|
|
|
|
/*
|
|
* Check for the CPU being offline, but only if the grace period
|
|
* is old enough. We don't need to worry about the CPU changing
|
|
* state: If we see it offline even once, it has been through a
|
|
* quiescent state.
|
|
*
|
|
* The reason for insisting that the grace period be at least
|
|
* one jiffy old is that CPUs that are not quite online and that
|
|
* have just gone offline can still execute RCU read-side critical
|
|
* sections.
|
|
*/
|
|
if (ULONG_CMP_GE(rdp->rsp->gp_start + 2, jiffies))
|
|
return 0; /* Grace period is not old enough. */
|
|
barrier();
|
|
if (cpu_is_offline(rdp->cpu)) {
|
|
trace_rcu_fqs(rdp->rsp->name, rdp->gpnum, rdp->cpu, "ofl");
|
|
rdp->offline_fqs++;
|
|
return 1;
|
|
}
|
|
return 0;
|
|
}
|
|
|
|
static void record_gp_stall_check_time(struct rcu_state *rsp)
|
|
{
|
|
rsp->gp_start = jiffies;
|
|
rsp->jiffies_stall = jiffies + rcu_jiffies_till_stall_check();
|
|
}
|
|
|
|
/*
|
|
* Dump stacks of all tasks running on stalled CPUs. This is a fallback
|
|
* for architectures that do not implement trigger_all_cpu_backtrace().
|
|
* The NMI-triggered stack traces are more accurate because they are
|
|
* printed by the target CPU.
|
|
*/
|
|
static void rcu_dump_cpu_stacks(struct rcu_state *rsp)
|
|
{
|
|
int cpu;
|
|
unsigned long flags;
|
|
struct rcu_node *rnp;
|
|
|
|
rcu_for_each_leaf_node(rsp, rnp) {
|
|
raw_spin_lock_irqsave(&rnp->lock, flags);
|
|
if (rnp->qsmask != 0) {
|
|
for (cpu = 0; cpu <= rnp->grphi - rnp->grplo; cpu++)
|
|
if (rnp->qsmask & (1UL << cpu))
|
|
dump_cpu_task(rnp->grplo + cpu);
|
|
}
|
|
raw_spin_unlock_irqrestore(&rnp->lock, flags);
|
|
}
|
|
}
|
|
|
|
static void print_other_cpu_stall(struct rcu_state *rsp)
|
|
{
|
|
int cpu;
|
|
long delta;
|
|
unsigned long flags;
|
|
int ndetected = 0;
|
|
struct rcu_node *rnp = rcu_get_root(rsp);
|
|
long totqlen = 0;
|
|
|
|
/* Only let one CPU complain about others per time interval. */
|
|
|
|
raw_spin_lock_irqsave(&rnp->lock, flags);
|
|
delta = jiffies - rsp->jiffies_stall;
|
|
if (delta < RCU_STALL_RAT_DELAY || !rcu_gp_in_progress(rsp)) {
|
|
raw_spin_unlock_irqrestore(&rnp->lock, flags);
|
|
return;
|
|
}
|
|
rsp->jiffies_stall = jiffies + 3 * rcu_jiffies_till_stall_check() + 3;
|
|
raw_spin_unlock_irqrestore(&rnp->lock, flags);
|
|
|
|
/*
|
|
* OK, time to rat on our buddy...
|
|
* See Documentation/RCU/stallwarn.txt for info on how to debug
|
|
* RCU CPU stall warnings.
|
|
*/
|
|
printk(KERN_ERR "INFO: %s detected stalls on CPUs/tasks:",
|
|
rsp->name);
|
|
print_cpu_stall_info_begin();
|
|
rcu_for_each_leaf_node(rsp, rnp) {
|
|
raw_spin_lock_irqsave(&rnp->lock, flags);
|
|
ndetected += rcu_print_task_stall(rnp);
|
|
if (rnp->qsmask != 0) {
|
|
for (cpu = 0; cpu <= rnp->grphi - rnp->grplo; cpu++)
|
|
if (rnp->qsmask & (1UL << cpu)) {
|
|
print_cpu_stall_info(rsp,
|
|
rnp->grplo + cpu);
|
|
ndetected++;
|
|
}
|
|
}
|
|
raw_spin_unlock_irqrestore(&rnp->lock, flags);
|
|
}
|
|
|
|
/*
|
|
* Now rat on any tasks that got kicked up to the root rcu_node
|
|
* due to CPU offlining.
|
|
*/
|
|
rnp = rcu_get_root(rsp);
|
|
raw_spin_lock_irqsave(&rnp->lock, flags);
|
|
ndetected += rcu_print_task_stall(rnp);
|
|
raw_spin_unlock_irqrestore(&rnp->lock, flags);
|
|
|
|
print_cpu_stall_info_end();
|
|
for_each_possible_cpu(cpu)
|
|
totqlen += per_cpu_ptr(rsp->rda, cpu)->qlen;
|
|
pr_cont("(detected by %d, t=%ld jiffies, g=%lu, c=%lu, q=%lu)\n",
|
|
smp_processor_id(), (long)(jiffies - rsp->gp_start),
|
|
rsp->gpnum, rsp->completed, totqlen);
|
|
if (ndetected == 0)
|
|
printk(KERN_ERR "INFO: Stall ended before state dump start\n");
|
|
else if (!trigger_all_cpu_backtrace())
|
|
rcu_dump_cpu_stacks(rsp);
|
|
|
|
/* Complain about tasks blocking the grace period. */
|
|
|
|
rcu_print_detail_task_stall(rsp);
|
|
|
|
force_quiescent_state(rsp); /* Kick them all. */
|
|
}
|
|
|
|
static void print_cpu_stall(struct rcu_state *rsp)
|
|
{
|
|
int cpu;
|
|
unsigned long flags;
|
|
struct rcu_node *rnp = rcu_get_root(rsp);
|
|
long totqlen = 0;
|
|
|
|
/*
|
|
* OK, time to rat on ourselves...
|
|
* See Documentation/RCU/stallwarn.txt for info on how to debug
|
|
* RCU CPU stall warnings.
|
|
*/
|
|
printk(KERN_ERR "INFO: %s self-detected stall on CPU", rsp->name);
|
|
print_cpu_stall_info_begin();
|
|
print_cpu_stall_info(rsp, smp_processor_id());
|
|
print_cpu_stall_info_end();
|
|
for_each_possible_cpu(cpu)
|
|
totqlen += per_cpu_ptr(rsp->rda, cpu)->qlen;
|
|
pr_cont(" (t=%lu jiffies g=%lu c=%lu q=%lu)\n",
|
|
jiffies - rsp->gp_start, rsp->gpnum, rsp->completed, totqlen);
|
|
if (!trigger_all_cpu_backtrace())
|
|
dump_stack();
|
|
|
|
raw_spin_lock_irqsave(&rnp->lock, flags);
|
|
if (ULONG_CMP_GE(jiffies, rsp->jiffies_stall))
|
|
rsp->jiffies_stall = jiffies +
|
|
3 * rcu_jiffies_till_stall_check() + 3;
|
|
raw_spin_unlock_irqrestore(&rnp->lock, flags);
|
|
|
|
set_need_resched(); /* kick ourselves to get things going. */
|
|
}
|
|
|
|
static void check_cpu_stall(struct rcu_state *rsp, struct rcu_data *rdp)
|
|
{
|
|
unsigned long j;
|
|
unsigned long js;
|
|
struct rcu_node *rnp;
|
|
|
|
if (rcu_cpu_stall_suppress)
|
|
return;
|
|
j = ACCESS_ONCE(jiffies);
|
|
js = ACCESS_ONCE(rsp->jiffies_stall);
|
|
rnp = rdp->mynode;
|
|
if (rcu_gp_in_progress(rsp) &&
|
|
(ACCESS_ONCE(rnp->qsmask) & rdp->grpmask) && ULONG_CMP_GE(j, js)) {
|
|
|
|
/* We haven't checked in, so go dump stack. */
|
|
print_cpu_stall(rsp);
|
|
|
|
} else if (rcu_gp_in_progress(rsp) &&
|
|
ULONG_CMP_GE(j, js + RCU_STALL_RAT_DELAY)) {
|
|
|
|
/* They had a few time units to dump stack, so complain. */
|
|
print_other_cpu_stall(rsp);
|
|
}
|
|
}
|
|
|
|
/**
|
|
* rcu_cpu_stall_reset - prevent further stall warnings in current grace period
|
|
*
|
|
* Set the stall-warning timeout way off into the future, thus preventing
|
|
* any RCU CPU stall-warning messages from appearing in the current set of
|
|
* RCU grace periods.
|
|
*
|
|
* The caller must disable hard irqs.
|
|
*/
|
|
void rcu_cpu_stall_reset(void)
|
|
{
|
|
struct rcu_state *rsp;
|
|
|
|
for_each_rcu_flavor(rsp)
|
|
rsp->jiffies_stall = jiffies + ULONG_MAX / 2;
|
|
}
|
|
|
|
/*
|
|
* Update CPU-local rcu_data state to record the newly noticed grace period.
|
|
* This is used both when we started the grace period and when we notice
|
|
* that someone else started the grace period. The caller must hold the
|
|
* ->lock of the leaf rcu_node structure corresponding to the current CPU,
|
|
* and must have irqs disabled.
|
|
*/
|
|
static void __note_new_gpnum(struct rcu_state *rsp, struct rcu_node *rnp, struct rcu_data *rdp)
|
|
{
|
|
if (rdp->gpnum != rnp->gpnum) {
|
|
/*
|
|
* If the current grace period is waiting for this CPU,
|
|
* set up to detect a quiescent state, otherwise don't
|
|
* go looking for one.
|
|
*/
|
|
rdp->gpnum = rnp->gpnum;
|
|
trace_rcu_grace_period(rsp->name, rdp->gpnum, "cpustart");
|
|
rdp->passed_quiesce = 0;
|
|
rdp->qs_pending = !!(rnp->qsmask & rdp->grpmask);
|
|
zero_cpu_stall_ticks(rdp);
|
|
}
|
|
}
|
|
|
|
static void note_new_gpnum(struct rcu_state *rsp, struct rcu_data *rdp)
|
|
{
|
|
unsigned long flags;
|
|
struct rcu_node *rnp;
|
|
|
|
local_irq_save(flags);
|
|
rnp = rdp->mynode;
|
|
if (rdp->gpnum == ACCESS_ONCE(rnp->gpnum) || /* outside lock. */
|
|
!raw_spin_trylock(&rnp->lock)) { /* irqs already off, so later. */
|
|
local_irq_restore(flags);
|
|
return;
|
|
}
|
|
__note_new_gpnum(rsp, rnp, rdp);
|
|
raw_spin_unlock_irqrestore(&rnp->lock, flags);
|
|
}
|
|
|
|
/*
|
|
* Did someone else start a new RCU grace period start since we last
|
|
* checked? Update local state appropriately if so. Must be called
|
|
* on the CPU corresponding to rdp.
|
|
*/
|
|
static int
|
|
check_for_new_grace_period(struct rcu_state *rsp, struct rcu_data *rdp)
|
|
{
|
|
unsigned long flags;
|
|
int ret = 0;
|
|
|
|
local_irq_save(flags);
|
|
if (rdp->gpnum != rsp->gpnum) {
|
|
note_new_gpnum(rsp, rdp);
|
|
ret = 1;
|
|
}
|
|
local_irq_restore(flags);
|
|
return ret;
|
|
}
|
|
|
|
/*
|
|
* Initialize the specified rcu_data structure's callback list to empty.
|
|
*/
|
|
static void init_callback_list(struct rcu_data *rdp)
|
|
{
|
|
int i;
|
|
|
|
rdp->nxtlist = NULL;
|
|
for (i = 0; i < RCU_NEXT_SIZE; i++)
|
|
rdp->nxttail[i] = &rdp->nxtlist;
|
|
init_nocb_callback_list(rdp);
|
|
}
|
|
|
|
/*
|
|
* Determine the value that ->completed will have at the end of the
|
|
* next subsequent grace period. This is used to tag callbacks so that
|
|
* a CPU can invoke callbacks in a timely fashion even if that CPU has
|
|
* been dyntick-idle for an extended period with callbacks under the
|
|
* influence of RCU_FAST_NO_HZ.
|
|
*
|
|
* The caller must hold rnp->lock with interrupts disabled.
|
|
*/
|
|
static unsigned long rcu_cbs_completed(struct rcu_state *rsp,
|
|
struct rcu_node *rnp)
|
|
{
|
|
/*
|
|
* If RCU is idle, we just wait for the next grace period.
|
|
* But we can only be sure that RCU is idle if we are looking
|
|
* at the root rcu_node structure -- otherwise, a new grace
|
|
* period might have started, but just not yet gotten around
|
|
* to initializing the current non-root rcu_node structure.
|
|
*/
|
|
if (rcu_get_root(rsp) == rnp && rnp->gpnum == rnp->completed)
|
|
return rnp->completed + 1;
|
|
|
|
/*
|
|
* Otherwise, wait for a possible partial grace period and
|
|
* then the subsequent full grace period.
|
|
*/
|
|
return rnp->completed + 2;
|
|
}
|
|
|
|
/*
|
|
* If there is room, assign a ->completed number to any callbacks on
|
|
* this CPU that have not already been assigned. Also accelerate any
|
|
* callbacks that were previously assigned a ->completed number that has
|
|
* since proven to be too conservative, which can happen if callbacks get
|
|
* assigned a ->completed number while RCU is idle, but with reference to
|
|
* a non-root rcu_node structure. This function is idempotent, so it does
|
|
* not hurt to call it repeatedly.
|
|
*
|
|
* The caller must hold rnp->lock with interrupts disabled.
|
|
*/
|
|
static void rcu_accelerate_cbs(struct rcu_state *rsp, struct rcu_node *rnp,
|
|
struct rcu_data *rdp)
|
|
{
|
|
unsigned long c;
|
|
int i;
|
|
|
|
/* If the CPU has no callbacks, nothing to do. */
|
|
if (!rdp->nxttail[RCU_NEXT_TAIL] || !*rdp->nxttail[RCU_DONE_TAIL])
|
|
return;
|
|
|
|
/*
|
|
* Starting from the sublist containing the callbacks most
|
|
* recently assigned a ->completed number and working down, find the
|
|
* first sublist that is not assignable to an upcoming grace period.
|
|
* Such a sublist has something in it (first two tests) and has
|
|
* a ->completed number assigned that will complete sooner than
|
|
* the ->completed number for newly arrived callbacks (last test).
|
|
*
|
|
* The key point is that any later sublist can be assigned the
|
|
* same ->completed number as the newly arrived callbacks, which
|
|
* means that the callbacks in any of these later sublist can be
|
|
* grouped into a single sublist, whether or not they have already
|
|
* been assigned a ->completed number.
|
|
*/
|
|
c = rcu_cbs_completed(rsp, rnp);
|
|
for (i = RCU_NEXT_TAIL - 1; i > RCU_DONE_TAIL; i--)
|
|
if (rdp->nxttail[i] != rdp->nxttail[i - 1] &&
|
|
!ULONG_CMP_GE(rdp->nxtcompleted[i], c))
|
|
break;
|
|
|
|
/*
|
|
* If there are no sublist for unassigned callbacks, leave.
|
|
* At the same time, advance "i" one sublist, so that "i" will
|
|
* index into the sublist where all the remaining callbacks should
|
|
* be grouped into.
|
|
*/
|
|
if (++i >= RCU_NEXT_TAIL)
|
|
return;
|
|
|
|
/*
|
|
* Assign all subsequent callbacks' ->completed number to the next
|
|
* full grace period and group them all in the sublist initially
|
|
* indexed by "i".
|
|
*/
|
|
for (; i <= RCU_NEXT_TAIL; i++) {
|
|
rdp->nxttail[i] = rdp->nxttail[RCU_NEXT_TAIL];
|
|
rdp->nxtcompleted[i] = c;
|
|
}
|
|
|
|
/* Trace depending on how much we were able to accelerate. */
|
|
if (!*rdp->nxttail[RCU_WAIT_TAIL])
|
|
trace_rcu_grace_period(rsp->name, rdp->gpnum, "AccWaitCB");
|
|
else
|
|
trace_rcu_grace_period(rsp->name, rdp->gpnum, "AccReadyCB");
|
|
}
|
|
|
|
/*
|
|
* Move any callbacks whose grace period has completed to the
|
|
* RCU_DONE_TAIL sublist, then compact the remaining sublists and
|
|
* assign ->completed numbers to any callbacks in the RCU_NEXT_TAIL
|
|
* sublist. This function is idempotent, so it does not hurt to
|
|
* invoke it repeatedly. As long as it is not invoked -too- often...
|
|
*
|
|
* The caller must hold rnp->lock with interrupts disabled.
|
|
*/
|
|
static void rcu_advance_cbs(struct rcu_state *rsp, struct rcu_node *rnp,
|
|
struct rcu_data *rdp)
|
|
{
|
|
int i, j;
|
|
|
|
/* If the CPU has no callbacks, nothing to do. */
|
|
if (!rdp->nxttail[RCU_NEXT_TAIL] || !*rdp->nxttail[RCU_DONE_TAIL])
|
|
return;
|
|
|
|
/*
|
|
* Find all callbacks whose ->completed numbers indicate that they
|
|
* are ready to invoke, and put them into the RCU_DONE_TAIL sublist.
|
|
*/
|
|
for (i = RCU_WAIT_TAIL; i < RCU_NEXT_TAIL; i++) {
|
|
if (ULONG_CMP_LT(rnp->completed, rdp->nxtcompleted[i]))
|
|
break;
|
|
rdp->nxttail[RCU_DONE_TAIL] = rdp->nxttail[i];
|
|
}
|
|
/* Clean up any sublist tail pointers that were misordered above. */
|
|
for (j = RCU_WAIT_TAIL; j < i; j++)
|
|
rdp->nxttail[j] = rdp->nxttail[RCU_DONE_TAIL];
|
|
|
|
/* Copy down callbacks to fill in empty sublists. */
|
|
for (j = RCU_WAIT_TAIL; i < RCU_NEXT_TAIL; i++, j++) {
|
|
if (rdp->nxttail[j] == rdp->nxttail[RCU_NEXT_TAIL])
|
|
break;
|
|
rdp->nxttail[j] = rdp->nxttail[i];
|
|
rdp->nxtcompleted[j] = rdp->nxtcompleted[i];
|
|
}
|
|
|
|
/* Classify any remaining callbacks. */
|
|
rcu_accelerate_cbs(rsp, rnp, rdp);
|
|
}
|
|
|
|
/*
|
|
* Advance this CPU's callbacks, but only if the current grace period
|
|
* has ended. This may be called only from the CPU to whom the rdp
|
|
* belongs. In addition, the corresponding leaf rcu_node structure's
|
|
* ->lock must be held by the caller, with irqs disabled.
|
|
*/
|
|
static void
|
|
__rcu_process_gp_end(struct rcu_state *rsp, struct rcu_node *rnp, struct rcu_data *rdp)
|
|
{
|
|
/* Did another grace period end? */
|
|
if (rdp->completed == rnp->completed) {
|
|
|
|
/* No, so just accelerate recent callbacks. */
|
|
rcu_accelerate_cbs(rsp, rnp, rdp);
|
|
|
|
} else {
|
|
|
|
/* Advance callbacks. */
|
|
rcu_advance_cbs(rsp, rnp, rdp);
|
|
|
|
/* Remember that we saw this grace-period completion. */
|
|
rdp->completed = rnp->completed;
|
|
trace_rcu_grace_period(rsp->name, rdp->gpnum, "cpuend");
|
|
|
|
/*
|
|
* If we were in an extended quiescent state, we may have
|
|
* missed some grace periods that others CPUs handled on
|
|
* our behalf. Catch up with this state to avoid noting
|
|
* spurious new grace periods. If another grace period
|
|
* has started, then rnp->gpnum will have advanced, so
|
|
* we will detect this later on. Of course, any quiescent
|
|
* states we found for the old GP are now invalid.
|
|
*/
|
|
if (ULONG_CMP_LT(rdp->gpnum, rdp->completed)) {
|
|
rdp->gpnum = rdp->completed;
|
|
rdp->passed_quiesce = 0;
|
|
}
|
|
|
|
/*
|
|
* If RCU does not need a quiescent state from this CPU,
|
|
* then make sure that this CPU doesn't go looking for one.
|
|
*/
|
|
if ((rnp->qsmask & rdp->grpmask) == 0)
|
|
rdp->qs_pending = 0;
|
|
}
|
|
}
|
|
|
|
/*
|
|
* Advance this CPU's callbacks, but only if the current grace period
|
|
* has ended. This may be called only from the CPU to whom the rdp
|
|
* belongs.
|
|
*/
|
|
static void
|
|
rcu_process_gp_end(struct rcu_state *rsp, struct rcu_data *rdp)
|
|
{
|
|
unsigned long flags;
|
|
struct rcu_node *rnp;
|
|
|
|
local_irq_save(flags);
|
|
rnp = rdp->mynode;
|
|
if (rdp->completed == ACCESS_ONCE(rnp->completed) || /* outside lock. */
|
|
!raw_spin_trylock(&rnp->lock)) { /* irqs already off, so later. */
|
|
local_irq_restore(flags);
|
|
return;
|
|
}
|
|
__rcu_process_gp_end(rsp, rnp, rdp);
|
|
raw_spin_unlock_irqrestore(&rnp->lock, flags);
|
|
}
|
|
|
|
/*
|
|
* Do per-CPU grace-period initialization for running CPU. The caller
|
|
* must hold the lock of the leaf rcu_node structure corresponding to
|
|
* this CPU.
|
|
*/
|
|
static void
|
|
rcu_start_gp_per_cpu(struct rcu_state *rsp, struct rcu_node *rnp, struct rcu_data *rdp)
|
|
{
|
|
/* Prior grace period ended, so advance callbacks for current CPU. */
|
|
__rcu_process_gp_end(rsp, rnp, rdp);
|
|
|
|
/* Set state so that this CPU will detect the next quiescent state. */
|
|
__note_new_gpnum(rsp, rnp, rdp);
|
|
}
|
|
|
|
/*
|
|
* Initialize a new grace period.
|
|
*/
|
|
static int rcu_gp_init(struct rcu_state *rsp)
|
|
{
|
|
struct rcu_data *rdp;
|
|
struct rcu_node *rnp = rcu_get_root(rsp);
|
|
|
|
raw_spin_lock_irq(&rnp->lock);
|
|
rsp->gp_flags = 0; /* Clear all flags: New grace period. */
|
|
|
|
if (rcu_gp_in_progress(rsp)) {
|
|
/* Grace period already in progress, don't start another. */
|
|
raw_spin_unlock_irq(&rnp->lock);
|
|
return 0;
|
|
}
|
|
|
|
/* Advance to a new grace period and initialize state. */
|
|
rsp->gpnum++;
|
|
trace_rcu_grace_period(rsp->name, rsp->gpnum, "start");
|
|
record_gp_stall_check_time(rsp);
|
|
raw_spin_unlock_irq(&rnp->lock);
|
|
|
|
/* Exclude any concurrent CPU-hotplug operations. */
|
|
mutex_lock(&rsp->onoff_mutex);
|
|
|
|
/*
|
|
* Set the quiescent-state-needed bits in all the rcu_node
|
|
* structures for all currently online CPUs in breadth-first order,
|
|
* starting from the root rcu_node structure, relying on the layout
|
|
* of the tree within the rsp->node[] array. Note that other CPUs
|
|
* will access only the leaves of the hierarchy, thus seeing that no
|
|
* grace period is in progress, at least until the corresponding
|
|
* leaf node has been initialized. In addition, we have excluded
|
|
* CPU-hotplug operations.
|
|
*
|
|
* The grace period cannot complete until the initialization
|
|
* process finishes, because this kthread handles both.
|
|
*/
|
|
rcu_for_each_node_breadth_first(rsp, rnp) {
|
|
raw_spin_lock_irq(&rnp->lock);
|
|
rdp = this_cpu_ptr(rsp->rda);
|
|
rcu_preempt_check_blocked_tasks(rnp);
|
|
rnp->qsmask = rnp->qsmaskinit;
|
|
rnp->gpnum = rsp->gpnum;
|
|
WARN_ON_ONCE(rnp->completed != rsp->completed);
|
|
rnp->completed = rsp->completed;
|
|
if (rnp == rdp->mynode)
|
|
rcu_start_gp_per_cpu(rsp, rnp, rdp);
|
|
rcu_preempt_boost_start_gp(rnp);
|
|
trace_rcu_grace_period_init(rsp->name, rnp->gpnum,
|
|
rnp->level, rnp->grplo,
|
|
rnp->grphi, rnp->qsmask);
|
|
raw_spin_unlock_irq(&rnp->lock);
|
|
#ifdef CONFIG_PROVE_RCU_DELAY
|
|
if ((random32() % (rcu_num_nodes * 8)) == 0)
|
|
schedule_timeout_uninterruptible(2);
|
|
#endif /* #ifdef CONFIG_PROVE_RCU_DELAY */
|
|
cond_resched();
|
|
}
|
|
|
|
mutex_unlock(&rsp->onoff_mutex);
|
|
return 1;
|
|
}
|
|
|
|
/*
|
|
* Do one round of quiescent-state forcing.
|
|
*/
|
|
int rcu_gp_fqs(struct rcu_state *rsp, int fqs_state_in)
|
|
{
|
|
int fqs_state = fqs_state_in;
|
|
struct rcu_node *rnp = rcu_get_root(rsp);
|
|
|
|
rsp->n_force_qs++;
|
|
if (fqs_state == RCU_SAVE_DYNTICK) {
|
|
/* Collect dyntick-idle snapshots. */
|
|
force_qs_rnp(rsp, dyntick_save_progress_counter);
|
|
fqs_state = RCU_FORCE_QS;
|
|
} else {
|
|
/* Handle dyntick-idle and offline CPUs. */
|
|
force_qs_rnp(rsp, rcu_implicit_dynticks_qs);
|
|
}
|
|
/* Clear flag to prevent immediate re-entry. */
|
|
if (ACCESS_ONCE(rsp->gp_flags) & RCU_GP_FLAG_FQS) {
|
|
raw_spin_lock_irq(&rnp->lock);
|
|
rsp->gp_flags &= ~RCU_GP_FLAG_FQS;
|
|
raw_spin_unlock_irq(&rnp->lock);
|
|
}
|
|
return fqs_state;
|
|
}
|
|
|
|
/*
|
|
* Clean up after the old grace period.
|
|
*/
|
|
static void rcu_gp_cleanup(struct rcu_state *rsp)
|
|
{
|
|
unsigned long gp_duration;
|
|
struct rcu_data *rdp;
|
|
struct rcu_node *rnp = rcu_get_root(rsp);
|
|
|
|
raw_spin_lock_irq(&rnp->lock);
|
|
gp_duration = jiffies - rsp->gp_start;
|
|
if (gp_duration > rsp->gp_max)
|
|
rsp->gp_max = gp_duration;
|
|
|
|
/*
|
|
* We know the grace period is complete, but to everyone else
|
|
* it appears to still be ongoing. But it is also the case
|
|
* that to everyone else it looks like there is nothing that
|
|
* they can do to advance the grace period. It is therefore
|
|
* safe for us to drop the lock in order to mark the grace
|
|
* period as completed in all of the rcu_node structures.
|
|
*/
|
|
raw_spin_unlock_irq(&rnp->lock);
|
|
|
|
/*
|
|
* Propagate new ->completed value to rcu_node structures so
|
|
* that other CPUs don't have to wait until the start of the next
|
|
* grace period to process their callbacks. This also avoids
|
|
* some nasty RCU grace-period initialization races by forcing
|
|
* the end of the current grace period to be completely recorded in
|
|
* all of the rcu_node structures before the beginning of the next
|
|
* grace period is recorded in any of the rcu_node structures.
|
|
*/
|
|
rcu_for_each_node_breadth_first(rsp, rnp) {
|
|
raw_spin_lock_irq(&rnp->lock);
|
|
rnp->completed = rsp->gpnum;
|
|
raw_spin_unlock_irq(&rnp->lock);
|
|
cond_resched();
|
|
}
|
|
rnp = rcu_get_root(rsp);
|
|
raw_spin_lock_irq(&rnp->lock);
|
|
|
|
rsp->completed = rsp->gpnum; /* Declare grace period done. */
|
|
trace_rcu_grace_period(rsp->name, rsp->completed, "end");
|
|
rsp->fqs_state = RCU_GP_IDLE;
|
|
rdp = this_cpu_ptr(rsp->rda);
|
|
if (cpu_needs_another_gp(rsp, rdp))
|
|
rsp->gp_flags = 1;
|
|
raw_spin_unlock_irq(&rnp->lock);
|
|
}
|
|
|
|
/*
|
|
* Body of kthread that handles grace periods.
|
|
*/
|
|
static int __noreturn rcu_gp_kthread(void *arg)
|
|
{
|
|
int fqs_state;
|
|
unsigned long j;
|
|
int ret;
|
|
struct rcu_state *rsp = arg;
|
|
struct rcu_node *rnp = rcu_get_root(rsp);
|
|
|
|
for (;;) {
|
|
|
|
/* Handle grace-period start. */
|
|
for (;;) {
|
|
wait_event_interruptible(rsp->gp_wq,
|
|
rsp->gp_flags &
|
|
RCU_GP_FLAG_INIT);
|
|
if ((rsp->gp_flags & RCU_GP_FLAG_INIT) &&
|
|
rcu_gp_init(rsp))
|
|
break;
|
|
cond_resched();
|
|
flush_signals(current);
|
|
}
|
|
|
|
/* Handle quiescent-state forcing. */
|
|
fqs_state = RCU_SAVE_DYNTICK;
|
|
j = jiffies_till_first_fqs;
|
|
if (j > HZ) {
|
|
j = HZ;
|
|
jiffies_till_first_fqs = HZ;
|
|
}
|
|
for (;;) {
|
|
rsp->jiffies_force_qs = jiffies + j;
|
|
ret = wait_event_interruptible_timeout(rsp->gp_wq,
|
|
(rsp->gp_flags & RCU_GP_FLAG_FQS) ||
|
|
(!ACCESS_ONCE(rnp->qsmask) &&
|
|
!rcu_preempt_blocked_readers_cgp(rnp)),
|
|
j);
|
|
/* If grace period done, leave loop. */
|
|
if (!ACCESS_ONCE(rnp->qsmask) &&
|
|
!rcu_preempt_blocked_readers_cgp(rnp))
|
|
break;
|
|
/* If time for quiescent-state forcing, do it. */
|
|
if (ret == 0 || (rsp->gp_flags & RCU_GP_FLAG_FQS)) {
|
|
fqs_state = rcu_gp_fqs(rsp, fqs_state);
|
|
cond_resched();
|
|
} else {
|
|
/* Deal with stray signal. */
|
|
cond_resched();
|
|
flush_signals(current);
|
|
}
|
|
j = jiffies_till_next_fqs;
|
|
if (j > HZ) {
|
|
j = HZ;
|
|
jiffies_till_next_fqs = HZ;
|
|
} else if (j < 1) {
|
|
j = 1;
|
|
jiffies_till_next_fqs = 1;
|
|
}
|
|
}
|
|
|
|
/* Handle grace-period end. */
|
|
rcu_gp_cleanup(rsp);
|
|
}
|
|
}
|
|
|
|
/*
|
|
* Start a new RCU grace period if warranted, re-initializing the hierarchy
|
|
* in preparation for detecting the next grace period. The caller must hold
|
|
* the root node's ->lock, which is released before return. Hard irqs must
|
|
* be disabled.
|
|
*
|
|
* Note that it is legal for a dying CPU (which is marked as offline) to
|
|
* invoke this function. This can happen when the dying CPU reports its
|
|
* quiescent state.
|
|
*/
|
|
static void
|
|
rcu_start_gp(struct rcu_state *rsp, unsigned long flags)
|
|
__releases(rcu_get_root(rsp)->lock)
|
|
{
|
|
struct rcu_data *rdp = this_cpu_ptr(rsp->rda);
|
|
struct rcu_node *rnp = rcu_get_root(rsp);
|
|
|
|
if (!rsp->gp_kthread ||
|
|
!cpu_needs_another_gp(rsp, rdp)) {
|
|
/*
|
|
* Either we have not yet spawned the grace-period
|
|
* task, this CPU does not need another grace period,
|
|
* or a grace period is already in progress.
|
|
* Either way, don't start a new grace period.
|
|
*/
|
|
raw_spin_unlock_irqrestore(&rnp->lock, flags);
|
|
return;
|
|
}
|
|
|
|
/*
|
|
* Because there is no grace period in progress right now,
|
|
* any callbacks we have up to this point will be satisfied
|
|
* by the next grace period. So this is a good place to
|
|
* assign a grace period number to recently posted callbacks.
|
|
*/
|
|
rcu_accelerate_cbs(rsp, rnp, rdp);
|
|
|
|
rsp->gp_flags = RCU_GP_FLAG_INIT;
|
|
raw_spin_unlock(&rnp->lock); /* Interrupts remain disabled. */
|
|
|
|
/* Ensure that CPU is aware of completion of last grace period. */
|
|
rcu_process_gp_end(rsp, rdp);
|
|
local_irq_restore(flags);
|
|
|
|
/* Wake up rcu_gp_kthread() to start the grace period. */
|
|
wake_up(&rsp->gp_wq);
|
|
}
|
|
|
|
/*
|
|
* Report a full set of quiescent states to the specified rcu_state
|
|
* data structure. This involves cleaning up after the prior grace
|
|
* period and letting rcu_start_gp() start up the next grace period
|
|
* if one is needed. Note that the caller must hold rnp->lock, as
|
|
* required by rcu_start_gp(), which will release it.
|
|
*/
|
|
static void rcu_report_qs_rsp(struct rcu_state *rsp, unsigned long flags)
|
|
__releases(rcu_get_root(rsp)->lock)
|
|
{
|
|
WARN_ON_ONCE(!rcu_gp_in_progress(rsp));
|
|
raw_spin_unlock_irqrestore(&rcu_get_root(rsp)->lock, flags);
|
|
wake_up(&rsp->gp_wq); /* Memory barrier implied by wake_up() path. */
|
|
}
|
|
|
|
/*
|
|
* Similar to rcu_report_qs_rdp(), for which it is a helper function.
|
|
* Allows quiescent states for a group of CPUs to be reported at one go
|
|
* to the specified rcu_node structure, though all the CPUs in the group
|
|
* must be represented by the same rcu_node structure (which need not be
|
|
* a leaf rcu_node structure, though it often will be). That structure's
|
|
* lock must be held upon entry, and it is released before return.
|
|
*/
|
|
static void
|
|
rcu_report_qs_rnp(unsigned long mask, struct rcu_state *rsp,
|
|
struct rcu_node *rnp, unsigned long flags)
|
|
__releases(rnp->lock)
|
|
{
|
|
struct rcu_node *rnp_c;
|
|
|
|
/* Walk up the rcu_node hierarchy. */
|
|
for (;;) {
|
|
if (!(rnp->qsmask & mask)) {
|
|
|
|
/* Our bit has already been cleared, so done. */
|
|
raw_spin_unlock_irqrestore(&rnp->lock, flags);
|
|
return;
|
|
}
|
|
rnp->qsmask &= ~mask;
|
|
trace_rcu_quiescent_state_report(rsp->name, rnp->gpnum,
|
|
mask, rnp->qsmask, rnp->level,
|
|
rnp->grplo, rnp->grphi,
|
|
!!rnp->gp_tasks);
|
|
if (rnp->qsmask != 0 || rcu_preempt_blocked_readers_cgp(rnp)) {
|
|
|
|
/* Other bits still set at this level, so done. */
|
|
raw_spin_unlock_irqrestore(&rnp->lock, flags);
|
|
return;
|
|
}
|
|
mask = rnp->grpmask;
|
|
if (rnp->parent == NULL) {
|
|
|
|
/* No more levels. Exit loop holding root lock. */
|
|
|
|
break;
|
|
}
|
|
raw_spin_unlock_irqrestore(&rnp->lock, flags);
|
|
rnp_c = rnp;
|
|
rnp = rnp->parent;
|
|
raw_spin_lock_irqsave(&rnp->lock, flags);
|
|
WARN_ON_ONCE(rnp_c->qsmask);
|
|
}
|
|
|
|
/*
|
|
* Get here if we are the last CPU to pass through a quiescent
|
|
* state for this grace period. Invoke rcu_report_qs_rsp()
|
|
* to clean up and start the next grace period if one is needed.
|
|
*/
|
|
rcu_report_qs_rsp(rsp, flags); /* releases rnp->lock. */
|
|
}
|
|
|
|
/*
|
|
* Record a quiescent state for the specified CPU to that CPU's rcu_data
|
|
* structure. This must be either called from the specified CPU, or
|
|
* called when the specified CPU is known to be offline (and when it is
|
|
* also known that no other CPU is concurrently trying to help the offline
|
|
* CPU). The lastcomp argument is used to make sure we are still in the
|
|
* grace period of interest. We don't want to end the current grace period
|
|
* based on quiescent states detected in an earlier grace period!
|
|
*/
|
|
static void
|
|
rcu_report_qs_rdp(int cpu, struct rcu_state *rsp, struct rcu_data *rdp)
|
|
{
|
|
unsigned long flags;
|
|
unsigned long mask;
|
|
struct rcu_node *rnp;
|
|
|
|
rnp = rdp->mynode;
|
|
raw_spin_lock_irqsave(&rnp->lock, flags);
|
|
if (rdp->passed_quiesce == 0 || rdp->gpnum != rnp->gpnum ||
|
|
rnp->completed == rnp->gpnum) {
|
|
|
|
/*
|
|
* The grace period in which this quiescent state was
|
|
* recorded has ended, so don't report it upwards.
|
|
* We will instead need a new quiescent state that lies
|
|
* within the current grace period.
|
|
*/
|
|
rdp->passed_quiesce = 0; /* need qs for new gp. */
|
|
raw_spin_unlock_irqrestore(&rnp->lock, flags);
|
|
return;
|
|
}
|
|
mask = rdp->grpmask;
|
|
if ((rnp->qsmask & mask) == 0) {
|
|
raw_spin_unlock_irqrestore(&rnp->lock, flags);
|
|
} else {
|
|
rdp->qs_pending = 0;
|
|
|
|
/*
|
|
* This GP can't end until cpu checks in, so all of our
|
|
* callbacks can be processed during the next GP.
|
|
*/
|
|
rcu_accelerate_cbs(rsp, rnp, rdp);
|
|
|
|
rcu_report_qs_rnp(mask, rsp, rnp, flags); /* rlses rnp->lock */
|
|
}
|
|
}
|
|
|
|
/*
|
|
* Check to see if there is a new grace period of which this CPU
|
|
* is not yet aware, and if so, set up local rcu_data state for it.
|
|
* Otherwise, see if this CPU has just passed through its first
|
|
* quiescent state for this grace period, and record that fact if so.
|
|
*/
|
|
static void
|
|
rcu_check_quiescent_state(struct rcu_state *rsp, struct rcu_data *rdp)
|
|
{
|
|
/* If there is now a new grace period, record and return. */
|
|
if (check_for_new_grace_period(rsp, rdp))
|
|
return;
|
|
|
|
/*
|
|
* Does this CPU still need to do its part for current grace period?
|
|
* If no, return and let the other CPUs do their part as well.
|
|
*/
|
|
if (!rdp->qs_pending)
|
|
return;
|
|
|
|
/*
|
|
* Was there a quiescent state since the beginning of the grace
|
|
* period? If no, then exit and wait for the next call.
|
|
*/
|
|
if (!rdp->passed_quiesce)
|
|
return;
|
|
|
|
/*
|
|
* Tell RCU we are done (but rcu_report_qs_rdp() will be the
|
|
* judge of that).
|
|
*/
|
|
rcu_report_qs_rdp(rdp->cpu, rsp, rdp);
|
|
}
|
|
|
|
#ifdef CONFIG_HOTPLUG_CPU
|
|
|
|
/*
|
|
* Send the specified CPU's RCU callbacks to the orphanage. The
|
|
* specified CPU must be offline, and the caller must hold the
|
|
* ->orphan_lock.
|
|
*/
|
|
static void
|
|
rcu_send_cbs_to_orphanage(int cpu, struct rcu_state *rsp,
|
|
struct rcu_node *rnp, struct rcu_data *rdp)
|
|
{
|
|
/* No-CBs CPUs do not have orphanable callbacks. */
|
|
if (is_nocb_cpu(rdp->cpu))
|
|
return;
|
|
|
|
/*
|
|
* Orphan the callbacks. First adjust the counts. This is safe
|
|
* because _rcu_barrier() excludes CPU-hotplug operations, so it
|
|
* cannot be running now. Thus no memory barrier is required.
|
|
*/
|
|
if (rdp->nxtlist != NULL) {
|
|
rsp->qlen_lazy += rdp->qlen_lazy;
|
|
rsp->qlen += rdp->qlen;
|
|
rdp->n_cbs_orphaned += rdp->qlen;
|
|
rdp->qlen_lazy = 0;
|
|
ACCESS_ONCE(rdp->qlen) = 0;
|
|
}
|
|
|
|
/*
|
|
* Next, move those callbacks still needing a grace period to
|
|
* the orphanage, where some other CPU will pick them up.
|
|
* Some of the callbacks might have gone partway through a grace
|
|
* period, but that is too bad. They get to start over because we
|
|
* cannot assume that grace periods are synchronized across CPUs.
|
|
* We don't bother updating the ->nxttail[] array yet, instead
|
|
* we just reset the whole thing later on.
|
|
*/
|
|
if (*rdp->nxttail[RCU_DONE_TAIL] != NULL) {
|
|
*rsp->orphan_nxttail = *rdp->nxttail[RCU_DONE_TAIL];
|
|
rsp->orphan_nxttail = rdp->nxttail[RCU_NEXT_TAIL];
|
|
*rdp->nxttail[RCU_DONE_TAIL] = NULL;
|
|
}
|
|
|
|
/*
|
|
* Then move the ready-to-invoke callbacks to the orphanage,
|
|
* where some other CPU will pick them up. These will not be
|
|
* required to pass though another grace period: They are done.
|
|
*/
|
|
if (rdp->nxtlist != NULL) {
|
|
*rsp->orphan_donetail = rdp->nxtlist;
|
|
rsp->orphan_donetail = rdp->nxttail[RCU_DONE_TAIL];
|
|
}
|
|
|
|
/* Finally, initialize the rcu_data structure's list to empty. */
|
|
init_callback_list(rdp);
|
|
}
|
|
|
|
/*
|
|
* Adopt the RCU callbacks from the specified rcu_state structure's
|
|
* orphanage. The caller must hold the ->orphan_lock.
|
|
*/
|
|
static void rcu_adopt_orphan_cbs(struct rcu_state *rsp)
|
|
{
|
|
int i;
|
|
struct rcu_data *rdp = __this_cpu_ptr(rsp->rda);
|
|
|
|
/* No-CBs CPUs are handled specially. */
|
|
if (rcu_nocb_adopt_orphan_cbs(rsp, rdp))
|
|
return;
|
|
|
|
/* Do the accounting first. */
|
|
rdp->qlen_lazy += rsp->qlen_lazy;
|
|
rdp->qlen += rsp->qlen;
|
|
rdp->n_cbs_adopted += rsp->qlen;
|
|
if (rsp->qlen_lazy != rsp->qlen)
|
|
rcu_idle_count_callbacks_posted();
|
|
rsp->qlen_lazy = 0;
|
|
rsp->qlen = 0;
|
|
|
|
/*
|
|
* We do not need a memory barrier here because the only way we
|
|
* can get here if there is an rcu_barrier() in flight is if
|
|
* we are the task doing the rcu_barrier().
|
|
*/
|
|
|
|
/* First adopt the ready-to-invoke callbacks. */
|
|
if (rsp->orphan_donelist != NULL) {
|
|
*rsp->orphan_donetail = *rdp->nxttail[RCU_DONE_TAIL];
|
|
*rdp->nxttail[RCU_DONE_TAIL] = rsp->orphan_donelist;
|
|
for (i = RCU_NEXT_SIZE - 1; i >= RCU_DONE_TAIL; i--)
|
|
if (rdp->nxttail[i] == rdp->nxttail[RCU_DONE_TAIL])
|
|
rdp->nxttail[i] = rsp->orphan_donetail;
|
|
rsp->orphan_donelist = NULL;
|
|
rsp->orphan_donetail = &rsp->orphan_donelist;
|
|
}
|
|
|
|
/* And then adopt the callbacks that still need a grace period. */
|
|
if (rsp->orphan_nxtlist != NULL) {
|
|
*rdp->nxttail[RCU_NEXT_TAIL] = rsp->orphan_nxtlist;
|
|
rdp->nxttail[RCU_NEXT_TAIL] = rsp->orphan_nxttail;
|
|
rsp->orphan_nxtlist = NULL;
|
|
rsp->orphan_nxttail = &rsp->orphan_nxtlist;
|
|
}
|
|
}
|
|
|
|
/*
|
|
* Trace the fact that this CPU is going offline.
|
|
*/
|
|
static void rcu_cleanup_dying_cpu(struct rcu_state *rsp)
|
|
{
|
|
RCU_TRACE(unsigned long mask);
|
|
RCU_TRACE(struct rcu_data *rdp = this_cpu_ptr(rsp->rda));
|
|
RCU_TRACE(struct rcu_node *rnp = rdp->mynode);
|
|
|
|
RCU_TRACE(mask = rdp->grpmask);
|
|
trace_rcu_grace_period(rsp->name,
|
|
rnp->gpnum + 1 - !!(rnp->qsmask & mask),
|
|
"cpuofl");
|
|
}
|
|
|
|
/*
|
|
* The CPU has been completely removed, and some other CPU is reporting
|
|
* this fact from process context. Do the remainder of the cleanup,
|
|
* including orphaning the outgoing CPU's RCU callbacks, and also
|
|
* adopting them. There can only be one CPU hotplug operation at a time,
|
|
* so no other CPU can be attempting to update rcu_cpu_kthread_task.
|
|
*/
|
|
static void rcu_cleanup_dead_cpu(int cpu, struct rcu_state *rsp)
|
|
{
|
|
unsigned long flags;
|
|
unsigned long mask;
|
|
int need_report = 0;
|
|
struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu);
|
|
struct rcu_node *rnp = rdp->mynode; /* Outgoing CPU's rdp & rnp. */
|
|
|
|
/* Adjust any no-longer-needed kthreads. */
|
|
rcu_boost_kthread_setaffinity(rnp, -1);
|
|
|
|
/* Remove the dead CPU from the bitmasks in the rcu_node hierarchy. */
|
|
|
|
/* Exclude any attempts to start a new grace period. */
|
|
mutex_lock(&rsp->onoff_mutex);
|
|
raw_spin_lock_irqsave(&rsp->orphan_lock, flags);
|
|
|
|
/* Orphan the dead CPU's callbacks, and adopt them if appropriate. */
|
|
rcu_send_cbs_to_orphanage(cpu, rsp, rnp, rdp);
|
|
rcu_adopt_orphan_cbs(rsp);
|
|
|
|
/* Remove the outgoing CPU from the masks in the rcu_node hierarchy. */
|
|
mask = rdp->grpmask; /* rnp->grplo is constant. */
|
|
do {
|
|
raw_spin_lock(&rnp->lock); /* irqs already disabled. */
|
|
rnp->qsmaskinit &= ~mask;
|
|
if (rnp->qsmaskinit != 0) {
|
|
if (rnp != rdp->mynode)
|
|
raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */
|
|
break;
|
|
}
|
|
if (rnp == rdp->mynode)
|
|
need_report = rcu_preempt_offline_tasks(rsp, rnp, rdp);
|
|
else
|
|
raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */
|
|
mask = rnp->grpmask;
|
|
rnp = rnp->parent;
|
|
} while (rnp != NULL);
|
|
|
|
/*
|
|
* We still hold the leaf rcu_node structure lock here, and
|
|
* irqs are still disabled. The reason for this subterfuge is
|
|
* because invoking rcu_report_unblock_qs_rnp() with ->orphan_lock
|
|
* held leads to deadlock.
|
|
*/
|
|
raw_spin_unlock(&rsp->orphan_lock); /* irqs remain disabled. */
|
|
rnp = rdp->mynode;
|
|
if (need_report & RCU_OFL_TASKS_NORM_GP)
|
|
rcu_report_unblock_qs_rnp(rnp, flags);
|
|
else
|
|
raw_spin_unlock_irqrestore(&rnp->lock, flags);
|
|
if (need_report & RCU_OFL_TASKS_EXP_GP)
|
|
rcu_report_exp_rnp(rsp, rnp, true);
|
|
WARN_ONCE(rdp->qlen != 0 || rdp->nxtlist != NULL,
|
|
"rcu_cleanup_dead_cpu: Callbacks on offline CPU %d: qlen=%lu, nxtlist=%p\n",
|
|
cpu, rdp->qlen, rdp->nxtlist);
|
|
init_callback_list(rdp);
|
|
/* Disallow further callbacks on this CPU. */
|
|
rdp->nxttail[RCU_NEXT_TAIL] = NULL;
|
|
mutex_unlock(&rsp->onoff_mutex);
|
|
}
|
|
|
|
#else /* #ifdef CONFIG_HOTPLUG_CPU */
|
|
|
|
static void rcu_cleanup_dying_cpu(struct rcu_state *rsp)
|
|
{
|
|
}
|
|
|
|
static void rcu_cleanup_dead_cpu(int cpu, struct rcu_state *rsp)
|
|
{
|
|
}
|
|
|
|
#endif /* #else #ifdef CONFIG_HOTPLUG_CPU */
|
|
|
|
/*
|
|
* Invoke any RCU callbacks that have made it to the end of their grace
|
|
* period. Thottle as specified by rdp->blimit.
|
|
*/
|
|
static void rcu_do_batch(struct rcu_state *rsp, struct rcu_data *rdp)
|
|
{
|
|
unsigned long flags;
|
|
struct rcu_head *next, *list, **tail;
|
|
long bl, count, count_lazy;
|
|
int i;
|
|
|
|
/* If no callbacks are ready, just return. */
|
|
if (!cpu_has_callbacks_ready_to_invoke(rdp)) {
|
|
trace_rcu_batch_start(rsp->name, rdp->qlen_lazy, rdp->qlen, 0);
|
|
trace_rcu_batch_end(rsp->name, 0, !!ACCESS_ONCE(rdp->nxtlist),
|
|
need_resched(), is_idle_task(current),
|
|
rcu_is_callbacks_kthread());
|
|
return;
|
|
}
|
|
|
|
/*
|
|
* Extract the list of ready callbacks, disabling to prevent
|
|
* races with call_rcu() from interrupt handlers.
|
|
*/
|
|
local_irq_save(flags);
|
|
WARN_ON_ONCE(cpu_is_offline(smp_processor_id()));
|
|
bl = rdp->blimit;
|
|
trace_rcu_batch_start(rsp->name, rdp->qlen_lazy, rdp->qlen, bl);
|
|
list = rdp->nxtlist;
|
|
rdp->nxtlist = *rdp->nxttail[RCU_DONE_TAIL];
|
|
*rdp->nxttail[RCU_DONE_TAIL] = NULL;
|
|
tail = rdp->nxttail[RCU_DONE_TAIL];
|
|
for (i = RCU_NEXT_SIZE - 1; i >= 0; i--)
|
|
if (rdp->nxttail[i] == rdp->nxttail[RCU_DONE_TAIL])
|
|
rdp->nxttail[i] = &rdp->nxtlist;
|
|
local_irq_restore(flags);
|
|
|
|
/* Invoke callbacks. */
|
|
count = count_lazy = 0;
|
|
while (list) {
|
|
next = list->next;
|
|
prefetch(next);
|
|
debug_rcu_head_unqueue(list);
|
|
if (__rcu_reclaim(rsp->name, list))
|
|
count_lazy++;
|
|
list = next;
|
|
/* Stop only if limit reached and CPU has something to do. */
|
|
if (++count >= bl &&
|
|
(need_resched() ||
|
|
(!is_idle_task(current) && !rcu_is_callbacks_kthread())))
|
|
break;
|
|
}
|
|
|
|
local_irq_save(flags);
|
|
trace_rcu_batch_end(rsp->name, count, !!list, need_resched(),
|
|
is_idle_task(current),
|
|
rcu_is_callbacks_kthread());
|
|
|
|
/* Update count, and requeue any remaining callbacks. */
|
|
if (list != NULL) {
|
|
*tail = rdp->nxtlist;
|
|
rdp->nxtlist = list;
|
|
for (i = 0; i < RCU_NEXT_SIZE; i++)
|
|
if (&rdp->nxtlist == rdp->nxttail[i])
|
|
rdp->nxttail[i] = tail;
|
|
else
|
|
break;
|
|
}
|
|
smp_mb(); /* List handling before counting for rcu_barrier(). */
|
|
rdp->qlen_lazy -= count_lazy;
|
|
ACCESS_ONCE(rdp->qlen) -= count;
|
|
rdp->n_cbs_invoked += count;
|
|
|
|
/* Reinstate batch limit if we have worked down the excess. */
|
|
if (rdp->blimit == LONG_MAX && rdp->qlen <= qlowmark)
|
|
rdp->blimit = blimit;
|
|
|
|
/* Reset ->qlen_last_fqs_check trigger if enough CBs have drained. */
|
|
if (rdp->qlen == 0 && rdp->qlen_last_fqs_check != 0) {
|
|
rdp->qlen_last_fqs_check = 0;
|
|
rdp->n_force_qs_snap = rsp->n_force_qs;
|
|
} else if (rdp->qlen < rdp->qlen_last_fqs_check - qhimark)
|
|
rdp->qlen_last_fqs_check = rdp->qlen;
|
|
WARN_ON_ONCE((rdp->nxtlist == NULL) != (rdp->qlen == 0));
|
|
|
|
local_irq_restore(flags);
|
|
|
|
/* Re-invoke RCU core processing if there are callbacks remaining. */
|
|
if (cpu_has_callbacks_ready_to_invoke(rdp))
|
|
invoke_rcu_core();
|
|
}
|
|
|
|
/*
|
|
* Check to see if this CPU is in a non-context-switch quiescent state
|
|
* (user mode or idle loop for rcu, non-softirq execution for rcu_bh).
|
|
* Also schedule RCU core processing.
|
|
*
|
|
* This function must be called from hardirq context. It is normally
|
|
* invoked from the scheduling-clock interrupt. If rcu_pending returns
|
|
* false, there is no point in invoking rcu_check_callbacks().
|
|
*/
|
|
void rcu_check_callbacks(int cpu, int user)
|
|
{
|
|
trace_rcu_utilization("Start scheduler-tick");
|
|
increment_cpu_stall_ticks();
|
|
if (user || rcu_is_cpu_rrupt_from_idle()) {
|
|
|
|
/*
|
|
* Get here if this CPU took its interrupt from user
|
|
* mode or from the idle loop, and if this is not a
|
|
* nested interrupt. In this case, the CPU is in
|
|
* a quiescent state, so note it.
|
|
*
|
|
* No memory barrier is required here because both
|
|
* rcu_sched_qs() and rcu_bh_qs() reference only CPU-local
|
|
* variables that other CPUs neither access nor modify,
|
|
* at least not while the corresponding CPU is online.
|
|
*/
|
|
|
|
rcu_sched_qs(cpu);
|
|
rcu_bh_qs(cpu);
|
|
|
|
} else if (!in_softirq()) {
|
|
|
|
/*
|
|
* Get here if this CPU did not take its interrupt from
|
|
* softirq, in other words, if it is not interrupting
|
|
* a rcu_bh read-side critical section. This is an _bh
|
|
* critical section, so note it.
|
|
*/
|
|
|
|
rcu_bh_qs(cpu);
|
|
}
|
|
rcu_preempt_check_callbacks(cpu);
|
|
if (rcu_pending(cpu))
|
|
invoke_rcu_core();
|
|
trace_rcu_utilization("End scheduler-tick");
|
|
}
|
|
|
|
/*
|
|
* Scan the leaf rcu_node structures, processing dyntick state for any that
|
|
* have not yet encountered a quiescent state, using the function specified.
|
|
* Also initiate boosting for any threads blocked on the root rcu_node.
|
|
*
|
|
* The caller must have suppressed start of new grace periods.
|
|
*/
|
|
static void force_qs_rnp(struct rcu_state *rsp, int (*f)(struct rcu_data *))
|
|
{
|
|
unsigned long bit;
|
|
int cpu;
|
|
unsigned long flags;
|
|
unsigned long mask;
|
|
struct rcu_node *rnp;
|
|
|
|
rcu_for_each_leaf_node(rsp, rnp) {
|
|
cond_resched();
|
|
mask = 0;
|
|
raw_spin_lock_irqsave(&rnp->lock, flags);
|
|
if (!rcu_gp_in_progress(rsp)) {
|
|
raw_spin_unlock_irqrestore(&rnp->lock, flags);
|
|
return;
|
|
}
|
|
if (rnp->qsmask == 0) {
|
|
rcu_initiate_boost(rnp, flags); /* releases rnp->lock */
|
|
continue;
|
|
}
|
|
cpu = rnp->grplo;
|
|
bit = 1;
|
|
for (; cpu <= rnp->grphi; cpu++, bit <<= 1) {
|
|
if ((rnp->qsmask & bit) != 0 &&
|
|
f(per_cpu_ptr(rsp->rda, cpu)))
|
|
mask |= bit;
|
|
}
|
|
if (mask != 0) {
|
|
|
|
/* rcu_report_qs_rnp() releases rnp->lock. */
|
|
rcu_report_qs_rnp(mask, rsp, rnp, flags);
|
|
continue;
|
|
}
|
|
raw_spin_unlock_irqrestore(&rnp->lock, flags);
|
|
}
|
|
rnp = rcu_get_root(rsp);
|
|
if (rnp->qsmask == 0) {
|
|
raw_spin_lock_irqsave(&rnp->lock, flags);
|
|
rcu_initiate_boost(rnp, flags); /* releases rnp->lock. */
|
|
}
|
|
}
|
|
|
|
/*
|
|
* Force quiescent states on reluctant CPUs, and also detect which
|
|
* CPUs are in dyntick-idle mode.
|
|
*/
|
|
static void force_quiescent_state(struct rcu_state *rsp)
|
|
{
|
|
unsigned long flags;
|
|
bool ret;
|
|
struct rcu_node *rnp;
|
|
struct rcu_node *rnp_old = NULL;
|
|
|
|
/* Funnel through hierarchy to reduce memory contention. */
|
|
rnp = per_cpu_ptr(rsp->rda, raw_smp_processor_id())->mynode;
|
|
for (; rnp != NULL; rnp = rnp->parent) {
|
|
ret = (ACCESS_ONCE(rsp->gp_flags) & RCU_GP_FLAG_FQS) ||
|
|
!raw_spin_trylock(&rnp->fqslock);
|
|
if (rnp_old != NULL)
|
|
raw_spin_unlock(&rnp_old->fqslock);
|
|
if (ret) {
|
|
rsp->n_force_qs_lh++;
|
|
return;
|
|
}
|
|
rnp_old = rnp;
|
|
}
|
|
/* rnp_old == rcu_get_root(rsp), rnp == NULL. */
|
|
|
|
/* Reached the root of the rcu_node tree, acquire lock. */
|
|
raw_spin_lock_irqsave(&rnp_old->lock, flags);
|
|
raw_spin_unlock(&rnp_old->fqslock);
|
|
if (ACCESS_ONCE(rsp->gp_flags) & RCU_GP_FLAG_FQS) {
|
|
rsp->n_force_qs_lh++;
|
|
raw_spin_unlock_irqrestore(&rnp_old->lock, flags);
|
|
return; /* Someone beat us to it. */
|
|
}
|
|
rsp->gp_flags |= RCU_GP_FLAG_FQS;
|
|
raw_spin_unlock_irqrestore(&rnp_old->lock, flags);
|
|
wake_up(&rsp->gp_wq); /* Memory barrier implied by wake_up() path. */
|
|
}
|
|
|
|
/*
|
|
* This does the RCU core processing work for the specified rcu_state
|
|
* and rcu_data structures. This may be called only from the CPU to
|
|
* whom the rdp belongs.
|
|
*/
|
|
static void
|
|
__rcu_process_callbacks(struct rcu_state *rsp)
|
|
{
|
|
unsigned long flags;
|
|
struct rcu_data *rdp = __this_cpu_ptr(rsp->rda);
|
|
|
|
WARN_ON_ONCE(rdp->beenonline == 0);
|
|
|
|
/* Handle the end of a grace period that some other CPU ended. */
|
|
rcu_process_gp_end(rsp, rdp);
|
|
|
|
/* Update RCU state based on any recent quiescent states. */
|
|
rcu_check_quiescent_state(rsp, rdp);
|
|
|
|
/* Does this CPU require a not-yet-started grace period? */
|
|
local_irq_save(flags);
|
|
if (cpu_needs_another_gp(rsp, rdp)) {
|
|
raw_spin_lock(&rcu_get_root(rsp)->lock); /* irqs disabled. */
|
|
rcu_start_gp(rsp, flags); /* releases above lock */
|
|
} else {
|
|
local_irq_restore(flags);
|
|
}
|
|
|
|
/* If there are callbacks ready, invoke them. */
|
|
if (cpu_has_callbacks_ready_to_invoke(rdp))
|
|
invoke_rcu_callbacks(rsp, rdp);
|
|
}
|
|
|
|
/*
|
|
* Do RCU core processing for the current CPU.
|
|
*/
|
|
static void rcu_process_callbacks(struct softirq_action *unused)
|
|
{
|
|
struct rcu_state *rsp;
|
|
|
|
if (cpu_is_offline(smp_processor_id()))
|
|
return;
|
|
trace_rcu_utilization("Start RCU core");
|
|
for_each_rcu_flavor(rsp)
|
|
__rcu_process_callbacks(rsp);
|
|
trace_rcu_utilization("End RCU core");
|
|
}
|
|
|
|
/*
|
|
* Schedule RCU callback invocation. If the specified type of RCU
|
|
* does not support RCU priority boosting, just do a direct call,
|
|
* otherwise wake up the per-CPU kernel kthread. Note that because we
|
|
* are running on the current CPU with interrupts disabled, the
|
|
* rcu_cpu_kthread_task cannot disappear out from under us.
|
|
*/
|
|
static void invoke_rcu_callbacks(struct rcu_state *rsp, struct rcu_data *rdp)
|
|
{
|
|
if (unlikely(!ACCESS_ONCE(rcu_scheduler_fully_active)))
|
|
return;
|
|
if (likely(!rsp->boost)) {
|
|
rcu_do_batch(rsp, rdp);
|
|
return;
|
|
}
|
|
invoke_rcu_callbacks_kthread();
|
|
}
|
|
|
|
static void invoke_rcu_core(void)
|
|
{
|
|
raise_softirq(RCU_SOFTIRQ);
|
|
}
|
|
|
|
/*
|
|
* Handle any core-RCU processing required by a call_rcu() invocation.
|
|
*/
|
|
static void __call_rcu_core(struct rcu_state *rsp, struct rcu_data *rdp,
|
|
struct rcu_head *head, unsigned long flags)
|
|
{
|
|
/*
|
|
* If called from an extended quiescent state, invoke the RCU
|
|
* core in order to force a re-evaluation of RCU's idleness.
|
|
*/
|
|
if (rcu_is_cpu_idle() && cpu_online(smp_processor_id()))
|
|
invoke_rcu_core();
|
|
|
|
/* If interrupts were disabled or CPU offline, don't invoke RCU core. */
|
|
if (irqs_disabled_flags(flags) || cpu_is_offline(smp_processor_id()))
|
|
return;
|
|
|
|
/*
|
|
* Force the grace period if too many callbacks or too long waiting.
|
|
* Enforce hysteresis, and don't invoke force_quiescent_state()
|
|
* if some other CPU has recently done so. Also, don't bother
|
|
* invoking force_quiescent_state() if the newly enqueued callback
|
|
* is the only one waiting for a grace period to complete.
|
|
*/
|
|
if (unlikely(rdp->qlen > rdp->qlen_last_fqs_check + qhimark)) {
|
|
|
|
/* Are we ignoring a completed grace period? */
|
|
rcu_process_gp_end(rsp, rdp);
|
|
check_for_new_grace_period(rsp, rdp);
|
|
|
|
/* Start a new grace period if one not already started. */
|
|
if (!rcu_gp_in_progress(rsp)) {
|
|
unsigned long nestflag;
|
|
struct rcu_node *rnp_root = rcu_get_root(rsp);
|
|
|
|
raw_spin_lock_irqsave(&rnp_root->lock, nestflag);
|
|
rcu_start_gp(rsp, nestflag); /* rlses rnp_root->lock */
|
|
} else {
|
|
/* Give the grace period a kick. */
|
|
rdp->blimit = LONG_MAX;
|
|
if (rsp->n_force_qs == rdp->n_force_qs_snap &&
|
|
*rdp->nxttail[RCU_DONE_TAIL] != head)
|
|
force_quiescent_state(rsp);
|
|
rdp->n_force_qs_snap = rsp->n_force_qs;
|
|
rdp->qlen_last_fqs_check = rdp->qlen;
|
|
}
|
|
}
|
|
}
|
|
|
|
/*
|
|
* Helper function for call_rcu() and friends. The cpu argument will
|
|
* normally be -1, indicating "currently running CPU". It may specify
|
|
* a CPU only if that CPU is a no-CBs CPU. Currently, only _rcu_barrier()
|
|
* is expected to specify a CPU.
|
|
*/
|
|
static void
|
|
__call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu),
|
|
struct rcu_state *rsp, int cpu, bool lazy)
|
|
{
|
|
unsigned long flags;
|
|
struct rcu_data *rdp;
|
|
|
|
WARN_ON_ONCE((unsigned long)head & 0x3); /* Misaligned rcu_head! */
|
|
debug_rcu_head_queue(head);
|
|
head->func = func;
|
|
head->next = NULL;
|
|
|
|
/*
|
|
* Opportunistically note grace-period endings and beginnings.
|
|
* Note that we might see a beginning right after we see an
|
|
* end, but never vice versa, since this CPU has to pass through
|
|
* a quiescent state betweentimes.
|
|
*/
|
|
local_irq_save(flags);
|
|
rdp = this_cpu_ptr(rsp->rda);
|
|
|
|
/* Add the callback to our list. */
|
|
if (unlikely(rdp->nxttail[RCU_NEXT_TAIL] == NULL) || cpu != -1) {
|
|
int offline;
|
|
|
|
if (cpu != -1)
|
|
rdp = per_cpu_ptr(rsp->rda, cpu);
|
|
offline = !__call_rcu_nocb(rdp, head, lazy);
|
|
WARN_ON_ONCE(offline);
|
|
/* _call_rcu() is illegal on offline CPU; leak the callback. */
|
|
local_irq_restore(flags);
|
|
return;
|
|
}
|
|
ACCESS_ONCE(rdp->qlen)++;
|
|
if (lazy)
|
|
rdp->qlen_lazy++;
|
|
else
|
|
rcu_idle_count_callbacks_posted();
|
|
smp_mb(); /* Count before adding callback for rcu_barrier(). */
|
|
*rdp->nxttail[RCU_NEXT_TAIL] = head;
|
|
rdp->nxttail[RCU_NEXT_TAIL] = &head->next;
|
|
|
|
if (__is_kfree_rcu_offset((unsigned long)func))
|
|
trace_rcu_kfree_callback(rsp->name, head, (unsigned long)func,
|
|
rdp->qlen_lazy, rdp->qlen);
|
|
else
|
|
trace_rcu_callback(rsp->name, head, rdp->qlen_lazy, rdp->qlen);
|
|
|
|
/* Go handle any RCU core processing required. */
|
|
__call_rcu_core(rsp, rdp, head, flags);
|
|
local_irq_restore(flags);
|
|
}
|
|
|
|
/*
|
|
* Queue an RCU-sched callback for invocation after a grace period.
|
|
*/
|
|
void call_rcu_sched(struct rcu_head *head, void (*func)(struct rcu_head *rcu))
|
|
{
|
|
__call_rcu(head, func, &rcu_sched_state, -1, 0);
|
|
}
|
|
EXPORT_SYMBOL_GPL(call_rcu_sched);
|
|
|
|
/*
|
|
* Queue an RCU callback for invocation after a quicker grace period.
|
|
*/
|
|
void call_rcu_bh(struct rcu_head *head, void (*func)(struct rcu_head *rcu))
|
|
{
|
|
__call_rcu(head, func, &rcu_bh_state, -1, 0);
|
|
}
|
|
EXPORT_SYMBOL_GPL(call_rcu_bh);
|
|
|
|
/*
|
|
* Because a context switch is a grace period for RCU-sched and RCU-bh,
|
|
* any blocking grace-period wait automatically implies a grace period
|
|
* if there is only one CPU online at any point time during execution
|
|
* of either synchronize_sched() or synchronize_rcu_bh(). It is OK to
|
|
* occasionally incorrectly indicate that there are multiple CPUs online
|
|
* when there was in fact only one the whole time, as this just adds
|
|
* some overhead: RCU still operates correctly.
|
|
*/
|
|
static inline int rcu_blocking_is_gp(void)
|
|
{
|
|
int ret;
|
|
|
|
might_sleep(); /* Check for RCU read-side critical section. */
|
|
preempt_disable();
|
|
ret = num_online_cpus() <= 1;
|
|
preempt_enable();
|
|
return ret;
|
|
}
|
|
|
|
/**
|
|
* synchronize_sched - wait until an rcu-sched grace period has elapsed.
|
|
*
|
|
* Control will return to the caller some time after a full rcu-sched
|
|
* grace period has elapsed, in other words after all currently executing
|
|
* rcu-sched read-side critical sections have completed. These read-side
|
|
* critical sections are delimited by rcu_read_lock_sched() and
|
|
* rcu_read_unlock_sched(), and may be nested. Note that preempt_disable(),
|
|
* local_irq_disable(), and so on may be used in place of
|
|
* rcu_read_lock_sched().
|
|
*
|
|
* This means that all preempt_disable code sequences, including NMI and
|
|
* non-threaded hardware-interrupt handlers, in progress on entry will
|
|
* have completed before this primitive returns. However, this does not
|
|
* guarantee that softirq handlers will have completed, since in some
|
|
* kernels, these handlers can run in process context, and can block.
|
|
*
|
|
* Note that this guarantee implies further memory-ordering guarantees.
|
|
* On systems with more than one CPU, when synchronize_sched() returns,
|
|
* each CPU is guaranteed to have executed a full memory barrier since the
|
|
* end of its last RCU-sched read-side critical section whose beginning
|
|
* preceded the call to synchronize_sched(). In addition, each CPU having
|
|
* an RCU read-side critical section that extends beyond the return from
|
|
* synchronize_sched() is guaranteed to have executed a full memory barrier
|
|
* after the beginning of synchronize_sched() and before the beginning of
|
|
* that RCU read-side critical section. Note that these guarantees include
|
|
* CPUs that are offline, idle, or executing in user mode, as well as CPUs
|
|
* that are executing in the kernel.
|
|
*
|
|
* Furthermore, if CPU A invoked synchronize_sched(), which returned
|
|
* to its caller on CPU B, then both CPU A and CPU B are guaranteed
|
|
* to have executed a full memory barrier during the execution of
|
|
* synchronize_sched() -- even if CPU A and CPU B are the same CPU (but
|
|
* again only if the system has more than one CPU).
|
|
*
|
|
* This primitive provides the guarantees made by the (now removed)
|
|
* synchronize_kernel() API. In contrast, synchronize_rcu() only
|
|
* guarantees that rcu_read_lock() sections will have completed.
|
|
* In "classic RCU", these two guarantees happen to be one and
|
|
* the same, but can differ in realtime RCU implementations.
|
|
*/
|
|
void synchronize_sched(void)
|
|
{
|
|
rcu_lockdep_assert(!lock_is_held(&rcu_bh_lock_map) &&
|
|
!lock_is_held(&rcu_lock_map) &&
|
|
!lock_is_held(&rcu_sched_lock_map),
|
|
"Illegal synchronize_sched() in RCU-sched read-side critical section");
|
|
if (rcu_blocking_is_gp())
|
|
return;
|
|
if (rcu_expedited)
|
|
synchronize_sched_expedited();
|
|
else
|
|
wait_rcu_gp(call_rcu_sched);
|
|
}
|
|
EXPORT_SYMBOL_GPL(synchronize_sched);
|
|
|
|
/**
|
|
* synchronize_rcu_bh - wait until an rcu_bh grace period has elapsed.
|
|
*
|
|
* Control will return to the caller some time after a full rcu_bh grace
|
|
* period has elapsed, in other words after all currently executing rcu_bh
|
|
* read-side critical sections have completed. RCU read-side critical
|
|
* sections are delimited by rcu_read_lock_bh() and rcu_read_unlock_bh(),
|
|
* and may be nested.
|
|
*
|
|
* See the description of synchronize_sched() for more detailed information
|
|
* on memory ordering guarantees.
|
|
*/
|
|
void synchronize_rcu_bh(void)
|
|
{
|
|
rcu_lockdep_assert(!lock_is_held(&rcu_bh_lock_map) &&
|
|
!lock_is_held(&rcu_lock_map) &&
|
|
!lock_is_held(&rcu_sched_lock_map),
|
|
"Illegal synchronize_rcu_bh() in RCU-bh read-side critical section");
|
|
if (rcu_blocking_is_gp())
|
|
return;
|
|
if (rcu_expedited)
|
|
synchronize_rcu_bh_expedited();
|
|
else
|
|
wait_rcu_gp(call_rcu_bh);
|
|
}
|
|
EXPORT_SYMBOL_GPL(synchronize_rcu_bh);
|
|
|
|
static int synchronize_sched_expedited_cpu_stop(void *data)
|
|
{
|
|
/*
|
|
* There must be a full memory barrier on each affected CPU
|
|
* between the time that try_stop_cpus() is called and the
|
|
* time that it returns.
|
|
*
|
|
* In the current initial implementation of cpu_stop, the
|
|
* above condition is already met when the control reaches
|
|
* this point and the following smp_mb() is not strictly
|
|
* necessary. Do smp_mb() anyway for documentation and
|
|
* robustness against future implementation changes.
|
|
*/
|
|
smp_mb(); /* See above comment block. */
|
|
return 0;
|
|
}
|
|
|
|
/**
|
|
* synchronize_sched_expedited - Brute-force RCU-sched grace period
|
|
*
|
|
* Wait for an RCU-sched grace period to elapse, but use a "big hammer"
|
|
* approach to force the grace period to end quickly. This consumes
|
|
* significant time on all CPUs and is unfriendly to real-time workloads,
|
|
* so is thus not recommended for any sort of common-case code. In fact,
|
|
* if you are using synchronize_sched_expedited() in a loop, please
|
|
* restructure your code to batch your updates, and then use a single
|
|
* synchronize_sched() instead.
|
|
*
|
|
* Note that it is illegal to call this function while holding any lock
|
|
* that is acquired by a CPU-hotplug notifier. And yes, it is also illegal
|
|
* to call this function from a CPU-hotplug notifier. Failing to observe
|
|
* these restriction will result in deadlock.
|
|
*
|
|
* This implementation can be thought of as an application of ticket
|
|
* locking to RCU, with sync_sched_expedited_started and
|
|
* sync_sched_expedited_done taking on the roles of the halves
|
|
* of the ticket-lock word. Each task atomically increments
|
|
* sync_sched_expedited_started upon entry, snapshotting the old value,
|
|
* then attempts to stop all the CPUs. If this succeeds, then each
|
|
* CPU will have executed a context switch, resulting in an RCU-sched
|
|
* grace period. We are then done, so we use atomic_cmpxchg() to
|
|
* update sync_sched_expedited_done to match our snapshot -- but
|
|
* only if someone else has not already advanced past our snapshot.
|
|
*
|
|
* On the other hand, if try_stop_cpus() fails, we check the value
|
|
* of sync_sched_expedited_done. If it has advanced past our
|
|
* initial snapshot, then someone else must have forced a grace period
|
|
* some time after we took our snapshot. In this case, our work is
|
|
* done for us, and we can simply return. Otherwise, we try again,
|
|
* but keep our initial snapshot for purposes of checking for someone
|
|
* doing our work for us.
|
|
*
|
|
* If we fail too many times in a row, we fall back to synchronize_sched().
|
|
*/
|
|
void synchronize_sched_expedited(void)
|
|
{
|
|
long firstsnap, s, snap;
|
|
int trycount = 0;
|
|
struct rcu_state *rsp = &rcu_sched_state;
|
|
|
|
/*
|
|
* If we are in danger of counter wrap, just do synchronize_sched().
|
|
* By allowing sync_sched_expedited_started to advance no more than
|
|
* ULONG_MAX/8 ahead of sync_sched_expedited_done, we are ensuring
|
|
* that more than 3.5 billion CPUs would be required to force a
|
|
* counter wrap on a 32-bit system. Quite a few more CPUs would of
|
|
* course be required on a 64-bit system.
|
|
*/
|
|
if (ULONG_CMP_GE((ulong)atomic_long_read(&rsp->expedited_start),
|
|
(ulong)atomic_long_read(&rsp->expedited_done) +
|
|
ULONG_MAX / 8)) {
|
|
synchronize_sched();
|
|
atomic_long_inc(&rsp->expedited_wrap);
|
|
return;
|
|
}
|
|
|
|
/*
|
|
* Take a ticket. Note that atomic_inc_return() implies a
|
|
* full memory barrier.
|
|
*/
|
|
snap = atomic_long_inc_return(&rsp->expedited_start);
|
|
firstsnap = snap;
|
|
get_online_cpus();
|
|
WARN_ON_ONCE(cpu_is_offline(raw_smp_processor_id()));
|
|
|
|
/*
|
|
* Each pass through the following loop attempts to force a
|
|
* context switch on each CPU.
|
|
*/
|
|
while (try_stop_cpus(cpu_online_mask,
|
|
synchronize_sched_expedited_cpu_stop,
|
|
NULL) == -EAGAIN) {
|
|
put_online_cpus();
|
|
atomic_long_inc(&rsp->expedited_tryfail);
|
|
|
|
/* Check to see if someone else did our work for us. */
|
|
s = atomic_long_read(&rsp->expedited_done);
|
|
if (ULONG_CMP_GE((ulong)s, (ulong)firstsnap)) {
|
|
/* ensure test happens before caller kfree */
|
|
smp_mb__before_atomic_inc(); /* ^^^ */
|
|
atomic_long_inc(&rsp->expedited_workdone1);
|
|
return;
|
|
}
|
|
|
|
/* No joy, try again later. Or just synchronize_sched(). */
|
|
if (trycount++ < 10) {
|
|
udelay(trycount * num_online_cpus());
|
|
} else {
|
|
wait_rcu_gp(call_rcu_sched);
|
|
atomic_long_inc(&rsp->expedited_normal);
|
|
return;
|
|
}
|
|
|
|
/* Recheck to see if someone else did our work for us. */
|
|
s = atomic_long_read(&rsp->expedited_done);
|
|
if (ULONG_CMP_GE((ulong)s, (ulong)firstsnap)) {
|
|
/* ensure test happens before caller kfree */
|
|
smp_mb__before_atomic_inc(); /* ^^^ */
|
|
atomic_long_inc(&rsp->expedited_workdone2);
|
|
return;
|
|
}
|
|
|
|
/*
|
|
* Refetching sync_sched_expedited_started allows later
|
|
* callers to piggyback on our grace period. We retry
|
|
* after they started, so our grace period works for them,
|
|
* and they started after our first try, so their grace
|
|
* period works for us.
|
|
*/
|
|
get_online_cpus();
|
|
snap = atomic_long_read(&rsp->expedited_start);
|
|
smp_mb(); /* ensure read is before try_stop_cpus(). */
|
|
}
|
|
atomic_long_inc(&rsp->expedited_stoppedcpus);
|
|
|
|
/*
|
|
* Everyone up to our most recent fetch is covered by our grace
|
|
* period. Update the counter, but only if our work is still
|
|
* relevant -- which it won't be if someone who started later
|
|
* than we did already did their update.
|
|
*/
|
|
do {
|
|
atomic_long_inc(&rsp->expedited_done_tries);
|
|
s = atomic_long_read(&rsp->expedited_done);
|
|
if (ULONG_CMP_GE((ulong)s, (ulong)snap)) {
|
|
/* ensure test happens before caller kfree */
|
|
smp_mb__before_atomic_inc(); /* ^^^ */
|
|
atomic_long_inc(&rsp->expedited_done_lost);
|
|
break;
|
|
}
|
|
} while (atomic_long_cmpxchg(&rsp->expedited_done, s, snap) != s);
|
|
atomic_long_inc(&rsp->expedited_done_exit);
|
|
|
|
put_online_cpus();
|
|
}
|
|
EXPORT_SYMBOL_GPL(synchronize_sched_expedited);
|
|
|
|
/*
|
|
* Check to see if there is any immediate RCU-related work to be done
|
|
* by the current CPU, for the specified type of RCU, returning 1 if so.
|
|
* The checks are in order of increasing expense: checks that can be
|
|
* carried out against CPU-local state are performed first. However,
|
|
* we must check for CPU stalls first, else we might not get a chance.
|
|
*/
|
|
static int __rcu_pending(struct rcu_state *rsp, struct rcu_data *rdp)
|
|
{
|
|
struct rcu_node *rnp = rdp->mynode;
|
|
|
|
rdp->n_rcu_pending++;
|
|
|
|
/* Check for CPU stalls, if enabled. */
|
|
check_cpu_stall(rsp, rdp);
|
|
|
|
/* Is the RCU core waiting for a quiescent state from this CPU? */
|
|
if (rcu_scheduler_fully_active &&
|
|
rdp->qs_pending && !rdp->passed_quiesce) {
|
|
rdp->n_rp_qs_pending++;
|
|
} else if (rdp->qs_pending && rdp->passed_quiesce) {
|
|
rdp->n_rp_report_qs++;
|
|
return 1;
|
|
}
|
|
|
|
/* Does this CPU have callbacks ready to invoke? */
|
|
if (cpu_has_callbacks_ready_to_invoke(rdp)) {
|
|
rdp->n_rp_cb_ready++;
|
|
return 1;
|
|
}
|
|
|
|
/* Has RCU gone idle with this CPU needing another grace period? */
|
|
if (cpu_needs_another_gp(rsp, rdp)) {
|
|
rdp->n_rp_cpu_needs_gp++;
|
|
return 1;
|
|
}
|
|
|
|
/* Has another RCU grace period completed? */
|
|
if (ACCESS_ONCE(rnp->completed) != rdp->completed) { /* outside lock */
|
|
rdp->n_rp_gp_completed++;
|
|
return 1;
|
|
}
|
|
|
|
/* Has a new RCU grace period started? */
|
|
if (ACCESS_ONCE(rnp->gpnum) != rdp->gpnum) { /* outside lock */
|
|
rdp->n_rp_gp_started++;
|
|
return 1;
|
|
}
|
|
|
|
/* nothing to do */
|
|
rdp->n_rp_need_nothing++;
|
|
return 0;
|
|
}
|
|
|
|
/*
|
|
* Check to see if there is any immediate RCU-related work to be done
|
|
* by the current CPU, returning 1 if so. This function is part of the
|
|
* RCU implementation; it is -not- an exported member of the RCU API.
|
|
*/
|
|
static int rcu_pending(int cpu)
|
|
{
|
|
struct rcu_state *rsp;
|
|
|
|
for_each_rcu_flavor(rsp)
|
|
if (__rcu_pending(rsp, per_cpu_ptr(rsp->rda, cpu)))
|
|
return 1;
|
|
return 0;
|
|
}
|
|
|
|
/*
|
|
* Check to see if any future RCU-related work will need to be done
|
|
* by the current CPU, even if none need be done immediately, returning
|
|
* 1 if so.
|
|
*/
|
|
static int rcu_cpu_has_callbacks(int cpu)
|
|
{
|
|
struct rcu_state *rsp;
|
|
|
|
/* RCU callbacks either ready or pending? */
|
|
for_each_rcu_flavor(rsp)
|
|
if (per_cpu_ptr(rsp->rda, cpu)->nxtlist)
|
|
return 1;
|
|
return 0;
|
|
}
|
|
|
|
/*
|
|
* Helper function for _rcu_barrier() tracing. If tracing is disabled,
|
|
* the compiler is expected to optimize this away.
|
|
*/
|
|
static void _rcu_barrier_trace(struct rcu_state *rsp, char *s,
|
|
int cpu, unsigned long done)
|
|
{
|
|
trace_rcu_barrier(rsp->name, s, cpu,
|
|
atomic_read(&rsp->barrier_cpu_count), done);
|
|
}
|
|
|
|
/*
|
|
* RCU callback function for _rcu_barrier(). If we are last, wake
|
|
* up the task executing _rcu_barrier().
|
|
*/
|
|
static void rcu_barrier_callback(struct rcu_head *rhp)
|
|
{
|
|
struct rcu_data *rdp = container_of(rhp, struct rcu_data, barrier_head);
|
|
struct rcu_state *rsp = rdp->rsp;
|
|
|
|
if (atomic_dec_and_test(&rsp->barrier_cpu_count)) {
|
|
_rcu_barrier_trace(rsp, "LastCB", -1, rsp->n_barrier_done);
|
|
complete(&rsp->barrier_completion);
|
|
} else {
|
|
_rcu_barrier_trace(rsp, "CB", -1, rsp->n_barrier_done);
|
|
}
|
|
}
|
|
|
|
/*
|
|
* Called with preemption disabled, and from cross-cpu IRQ context.
|
|
*/
|
|
static void rcu_barrier_func(void *type)
|
|
{
|
|
struct rcu_state *rsp = type;
|
|
struct rcu_data *rdp = __this_cpu_ptr(rsp->rda);
|
|
|
|
_rcu_barrier_trace(rsp, "IRQ", -1, rsp->n_barrier_done);
|
|
atomic_inc(&rsp->barrier_cpu_count);
|
|
rsp->call(&rdp->barrier_head, rcu_barrier_callback);
|
|
}
|
|
|
|
/*
|
|
* Orchestrate the specified type of RCU barrier, waiting for all
|
|
* RCU callbacks of the specified type to complete.
|
|
*/
|
|
static void _rcu_barrier(struct rcu_state *rsp)
|
|
{
|
|
int cpu;
|
|
struct rcu_data *rdp;
|
|
unsigned long snap = ACCESS_ONCE(rsp->n_barrier_done);
|
|
unsigned long snap_done;
|
|
|
|
_rcu_barrier_trace(rsp, "Begin", -1, snap);
|
|
|
|
/* Take mutex to serialize concurrent rcu_barrier() requests. */
|
|
mutex_lock(&rsp->barrier_mutex);
|
|
|
|
/*
|
|
* Ensure that all prior references, including to ->n_barrier_done,
|
|
* are ordered before the _rcu_barrier() machinery.
|
|
*/
|
|
smp_mb(); /* See above block comment. */
|
|
|
|
/*
|
|
* Recheck ->n_barrier_done to see if others did our work for us.
|
|
* This means checking ->n_barrier_done for an even-to-odd-to-even
|
|
* transition. The "if" expression below therefore rounds the old
|
|
* value up to the next even number and adds two before comparing.
|
|
*/
|
|
snap_done = ACCESS_ONCE(rsp->n_barrier_done);
|
|
_rcu_barrier_trace(rsp, "Check", -1, snap_done);
|
|
if (ULONG_CMP_GE(snap_done, ((snap + 1) & ~0x1) + 2)) {
|
|
_rcu_barrier_trace(rsp, "EarlyExit", -1, snap_done);
|
|
smp_mb(); /* caller's subsequent code after above check. */
|
|
mutex_unlock(&rsp->barrier_mutex);
|
|
return;
|
|
}
|
|
|
|
/*
|
|
* Increment ->n_barrier_done to avoid duplicate work. Use
|
|
* ACCESS_ONCE() to prevent the compiler from speculating
|
|
* the increment to precede the early-exit check.
|
|
*/
|
|
ACCESS_ONCE(rsp->n_barrier_done)++;
|
|
WARN_ON_ONCE((rsp->n_barrier_done & 0x1) != 1);
|
|
_rcu_barrier_trace(rsp, "Inc1", -1, rsp->n_barrier_done);
|
|
smp_mb(); /* Order ->n_barrier_done increment with below mechanism. */
|
|
|
|
/*
|
|
* Initialize the count to one rather than to zero in order to
|
|
* avoid a too-soon return to zero in case of a short grace period
|
|
* (or preemption of this task). Exclude CPU-hotplug operations
|
|
* to ensure that no offline CPU has callbacks queued.
|
|
*/
|
|
init_completion(&rsp->barrier_completion);
|
|
atomic_set(&rsp->barrier_cpu_count, 1);
|
|
get_online_cpus();
|
|
|
|
/*
|
|
* Force each CPU with callbacks to register a new callback.
|
|
* When that callback is invoked, we will know that all of the
|
|
* corresponding CPU's preceding callbacks have been invoked.
|
|
*/
|
|
for_each_possible_cpu(cpu) {
|
|
if (!cpu_online(cpu) && !is_nocb_cpu(cpu))
|
|
continue;
|
|
rdp = per_cpu_ptr(rsp->rda, cpu);
|
|
if (is_nocb_cpu(cpu)) {
|
|
_rcu_barrier_trace(rsp, "OnlineNoCB", cpu,
|
|
rsp->n_barrier_done);
|
|
atomic_inc(&rsp->barrier_cpu_count);
|
|
__call_rcu(&rdp->barrier_head, rcu_barrier_callback,
|
|
rsp, cpu, 0);
|
|
} else if (ACCESS_ONCE(rdp->qlen)) {
|
|
_rcu_barrier_trace(rsp, "OnlineQ", cpu,
|
|
rsp->n_barrier_done);
|
|
smp_call_function_single(cpu, rcu_barrier_func, rsp, 1);
|
|
} else {
|
|
_rcu_barrier_trace(rsp, "OnlineNQ", cpu,
|
|
rsp->n_barrier_done);
|
|
}
|
|
}
|
|
put_online_cpus();
|
|
|
|
/*
|
|
* Now that we have an rcu_barrier_callback() callback on each
|
|
* CPU, and thus each counted, remove the initial count.
|
|
*/
|
|
if (atomic_dec_and_test(&rsp->barrier_cpu_count))
|
|
complete(&rsp->barrier_completion);
|
|
|
|
/* Increment ->n_barrier_done to prevent duplicate work. */
|
|
smp_mb(); /* Keep increment after above mechanism. */
|
|
ACCESS_ONCE(rsp->n_barrier_done)++;
|
|
WARN_ON_ONCE((rsp->n_barrier_done & 0x1) != 0);
|
|
_rcu_barrier_trace(rsp, "Inc2", -1, rsp->n_barrier_done);
|
|
smp_mb(); /* Keep increment before caller's subsequent code. */
|
|
|
|
/* Wait for all rcu_barrier_callback() callbacks to be invoked. */
|
|
wait_for_completion(&rsp->barrier_completion);
|
|
|
|
/* Other rcu_barrier() invocations can now safely proceed. */
|
|
mutex_unlock(&rsp->barrier_mutex);
|
|
}
|
|
|
|
/**
|
|
* rcu_barrier_bh - Wait until all in-flight call_rcu_bh() callbacks complete.
|
|
*/
|
|
void rcu_barrier_bh(void)
|
|
{
|
|
_rcu_barrier(&rcu_bh_state);
|
|
}
|
|
EXPORT_SYMBOL_GPL(rcu_barrier_bh);
|
|
|
|
/**
|
|
* rcu_barrier_sched - Wait for in-flight call_rcu_sched() callbacks.
|
|
*/
|
|
void rcu_barrier_sched(void)
|
|
{
|
|
_rcu_barrier(&rcu_sched_state);
|
|
}
|
|
EXPORT_SYMBOL_GPL(rcu_barrier_sched);
|
|
|
|
/*
|
|
* Do boot-time initialization of a CPU's per-CPU RCU data.
|
|
*/
|
|
static void __init
|
|
rcu_boot_init_percpu_data(int cpu, struct rcu_state *rsp)
|
|
{
|
|
unsigned long flags;
|
|
struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu);
|
|
struct rcu_node *rnp = rcu_get_root(rsp);
|
|
|
|
/* Set up local state, ensuring consistent view of global state. */
|
|
raw_spin_lock_irqsave(&rnp->lock, flags);
|
|
rdp->grpmask = 1UL << (cpu - rdp->mynode->grplo);
|
|
init_callback_list(rdp);
|
|
rdp->qlen_lazy = 0;
|
|
ACCESS_ONCE(rdp->qlen) = 0;
|
|
rdp->dynticks = &per_cpu(rcu_dynticks, cpu);
|
|
WARN_ON_ONCE(rdp->dynticks->dynticks_nesting != DYNTICK_TASK_EXIT_IDLE);
|
|
WARN_ON_ONCE(atomic_read(&rdp->dynticks->dynticks) != 1);
|
|
rdp->cpu = cpu;
|
|
rdp->rsp = rsp;
|
|
rcu_boot_init_nocb_percpu_data(rdp);
|
|
raw_spin_unlock_irqrestore(&rnp->lock, flags);
|
|
}
|
|
|
|
/*
|
|
* Initialize a CPU's per-CPU RCU data. Note that only one online or
|
|
* offline event can be happening at a given time. Note also that we
|
|
* can accept some slop in the rsp->completed access due to the fact
|
|
* that this CPU cannot possibly have any RCU callbacks in flight yet.
|
|
*/
|
|
static void __cpuinit
|
|
rcu_init_percpu_data(int cpu, struct rcu_state *rsp, int preemptible)
|
|
{
|
|
unsigned long flags;
|
|
unsigned long mask;
|
|
struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu);
|
|
struct rcu_node *rnp = rcu_get_root(rsp);
|
|
|
|
/* Exclude new grace periods. */
|
|
mutex_lock(&rsp->onoff_mutex);
|
|
|
|
/* Set up local state, ensuring consistent view of global state. */
|
|
raw_spin_lock_irqsave(&rnp->lock, flags);
|
|
rdp->beenonline = 1; /* We have now been online. */
|
|
rdp->preemptible = preemptible;
|
|
rdp->qlen_last_fqs_check = 0;
|
|
rdp->n_force_qs_snap = rsp->n_force_qs;
|
|
rdp->blimit = blimit;
|
|
init_callback_list(rdp); /* Re-enable callbacks on this CPU. */
|
|
rdp->dynticks->dynticks_nesting = DYNTICK_TASK_EXIT_IDLE;
|
|
atomic_set(&rdp->dynticks->dynticks,
|
|
(atomic_read(&rdp->dynticks->dynticks) & ~0x1) + 1);
|
|
rcu_prepare_for_idle_init(cpu);
|
|
raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */
|
|
|
|
/* Add CPU to rcu_node bitmasks. */
|
|
rnp = rdp->mynode;
|
|
mask = rdp->grpmask;
|
|
do {
|
|
/* Exclude any attempts to start a new GP on small systems. */
|
|
raw_spin_lock(&rnp->lock); /* irqs already disabled. */
|
|
rnp->qsmaskinit |= mask;
|
|
mask = rnp->grpmask;
|
|
if (rnp == rdp->mynode) {
|
|
/*
|
|
* If there is a grace period in progress, we will
|
|
* set up to wait for it next time we run the
|
|
* RCU core code.
|
|
*/
|
|
rdp->gpnum = rnp->completed;
|
|
rdp->completed = rnp->completed;
|
|
rdp->passed_quiesce = 0;
|
|
rdp->qs_pending = 0;
|
|
trace_rcu_grace_period(rsp->name, rdp->gpnum, "cpuonl");
|
|
}
|
|
raw_spin_unlock(&rnp->lock); /* irqs already disabled. */
|
|
rnp = rnp->parent;
|
|
} while (rnp != NULL && !(rnp->qsmaskinit & mask));
|
|
local_irq_restore(flags);
|
|
|
|
mutex_unlock(&rsp->onoff_mutex);
|
|
}
|
|
|
|
static void __cpuinit rcu_prepare_cpu(int cpu)
|
|
{
|
|
struct rcu_state *rsp;
|
|
|
|
for_each_rcu_flavor(rsp)
|
|
rcu_init_percpu_data(cpu, rsp,
|
|
strcmp(rsp->name, "rcu_preempt") == 0);
|
|
}
|
|
|
|
/*
|
|
* Handle CPU online/offline notification events.
|
|
*/
|
|
static int __cpuinit rcu_cpu_notify(struct notifier_block *self,
|
|
unsigned long action, void *hcpu)
|
|
{
|
|
long cpu = (long)hcpu;
|
|
struct rcu_data *rdp = per_cpu_ptr(rcu_state->rda, cpu);
|
|
struct rcu_node *rnp = rdp->mynode;
|
|
struct rcu_state *rsp;
|
|
int ret = NOTIFY_OK;
|
|
|
|
trace_rcu_utilization("Start CPU hotplug");
|
|
switch (action) {
|
|
case CPU_UP_PREPARE:
|
|
case CPU_UP_PREPARE_FROZEN:
|
|
rcu_prepare_cpu(cpu);
|
|
rcu_prepare_kthreads(cpu);
|
|
break;
|
|
case CPU_ONLINE:
|
|
case CPU_DOWN_FAILED:
|
|
rcu_boost_kthread_setaffinity(rnp, -1);
|
|
break;
|
|
case CPU_DOWN_PREPARE:
|
|
if (nocb_cpu_expendable(cpu))
|
|
rcu_boost_kthread_setaffinity(rnp, cpu);
|
|
else
|
|
ret = NOTIFY_BAD;
|
|
break;
|
|
case CPU_DYING:
|
|
case CPU_DYING_FROZEN:
|
|
/*
|
|
* The whole machine is "stopped" except this CPU, so we can
|
|
* touch any data without introducing corruption. We send the
|
|
* dying CPU's callbacks to an arbitrarily chosen online CPU.
|
|
*/
|
|
for_each_rcu_flavor(rsp)
|
|
rcu_cleanup_dying_cpu(rsp);
|
|
rcu_cleanup_after_idle(cpu);
|
|
break;
|
|
case CPU_DEAD:
|
|
case CPU_DEAD_FROZEN:
|
|
case CPU_UP_CANCELED:
|
|
case CPU_UP_CANCELED_FROZEN:
|
|
for_each_rcu_flavor(rsp)
|
|
rcu_cleanup_dead_cpu(cpu, rsp);
|
|
break;
|
|
default:
|
|
break;
|
|
}
|
|
trace_rcu_utilization("End CPU hotplug");
|
|
return ret;
|
|
}
|
|
|
|
/*
|
|
* Spawn the kthread that handles this RCU flavor's grace periods.
|
|
*/
|
|
static int __init rcu_spawn_gp_kthread(void)
|
|
{
|
|
unsigned long flags;
|
|
struct rcu_node *rnp;
|
|
struct rcu_state *rsp;
|
|
struct task_struct *t;
|
|
|
|
for_each_rcu_flavor(rsp) {
|
|
t = kthread_run(rcu_gp_kthread, rsp, rsp->name);
|
|
BUG_ON(IS_ERR(t));
|
|
rnp = rcu_get_root(rsp);
|
|
raw_spin_lock_irqsave(&rnp->lock, flags);
|
|
rsp->gp_kthread = t;
|
|
raw_spin_unlock_irqrestore(&rnp->lock, flags);
|
|
rcu_spawn_nocb_kthreads(rsp);
|
|
}
|
|
return 0;
|
|
}
|
|
early_initcall(rcu_spawn_gp_kthread);
|
|
|
|
/*
|
|
* This function is invoked towards the end of the scheduler's initialization
|
|
* process. Before this is called, the idle task might contain
|
|
* RCU read-side critical sections (during which time, this idle
|
|
* task is booting the system). After this function is called, the
|
|
* idle tasks are prohibited from containing RCU read-side critical
|
|
* sections. This function also enables RCU lockdep checking.
|
|
*/
|
|
void rcu_scheduler_starting(void)
|
|
{
|
|
WARN_ON(num_online_cpus() != 1);
|
|
WARN_ON(nr_context_switches() > 0);
|
|
rcu_scheduler_active = 1;
|
|
}
|
|
|
|
/*
|
|
* Compute the per-level fanout, either using the exact fanout specified
|
|
* or balancing the tree, depending on CONFIG_RCU_FANOUT_EXACT.
|
|
*/
|
|
#ifdef CONFIG_RCU_FANOUT_EXACT
|
|
static void __init rcu_init_levelspread(struct rcu_state *rsp)
|
|
{
|
|
int i;
|
|
|
|
for (i = rcu_num_lvls - 1; i > 0; i--)
|
|
rsp->levelspread[i] = CONFIG_RCU_FANOUT;
|
|
rsp->levelspread[0] = rcu_fanout_leaf;
|
|
}
|
|
#else /* #ifdef CONFIG_RCU_FANOUT_EXACT */
|
|
static void __init rcu_init_levelspread(struct rcu_state *rsp)
|
|
{
|
|
int ccur;
|
|
int cprv;
|
|
int i;
|
|
|
|
cprv = nr_cpu_ids;
|
|
for (i = rcu_num_lvls - 1; i >= 0; i--) {
|
|
ccur = rsp->levelcnt[i];
|
|
rsp->levelspread[i] = (cprv + ccur - 1) / ccur;
|
|
cprv = ccur;
|
|
}
|
|
}
|
|
#endif /* #else #ifdef CONFIG_RCU_FANOUT_EXACT */
|
|
|
|
/*
|
|
* Helper function for rcu_init() that initializes one rcu_state structure.
|
|
*/
|
|
static void __init rcu_init_one(struct rcu_state *rsp,
|
|
struct rcu_data __percpu *rda)
|
|
{
|
|
static char *buf[] = { "rcu_node_0",
|
|
"rcu_node_1",
|
|
"rcu_node_2",
|
|
"rcu_node_3" }; /* Match MAX_RCU_LVLS */
|
|
static char *fqs[] = { "rcu_node_fqs_0",
|
|
"rcu_node_fqs_1",
|
|
"rcu_node_fqs_2",
|
|
"rcu_node_fqs_3" }; /* Match MAX_RCU_LVLS */
|
|
int cpustride = 1;
|
|
int i;
|
|
int j;
|
|
struct rcu_node *rnp;
|
|
|
|
BUILD_BUG_ON(MAX_RCU_LVLS > ARRAY_SIZE(buf)); /* Fix buf[] init! */
|
|
|
|
/* Silence gcc 4.8 warning about array index out of range. */
|
|
if (rcu_num_lvls > RCU_NUM_LVLS)
|
|
panic("rcu_init_one: rcu_num_lvls overflow");
|
|
|
|
/* Initialize the level-tracking arrays. */
|
|
|
|
for (i = 0; i < rcu_num_lvls; i++)
|
|
rsp->levelcnt[i] = num_rcu_lvl[i];
|
|
for (i = 1; i < rcu_num_lvls; i++)
|
|
rsp->level[i] = rsp->level[i - 1] + rsp->levelcnt[i - 1];
|
|
rcu_init_levelspread(rsp);
|
|
|
|
/* Initialize the elements themselves, starting from the leaves. */
|
|
|
|
for (i = rcu_num_lvls - 1; i >= 0; i--) {
|
|
cpustride *= rsp->levelspread[i];
|
|
rnp = rsp->level[i];
|
|
for (j = 0; j < rsp->levelcnt[i]; j++, rnp++) {
|
|
raw_spin_lock_init(&rnp->lock);
|
|
lockdep_set_class_and_name(&rnp->lock,
|
|
&rcu_node_class[i], buf[i]);
|
|
raw_spin_lock_init(&rnp->fqslock);
|
|
lockdep_set_class_and_name(&rnp->fqslock,
|
|
&rcu_fqs_class[i], fqs[i]);
|
|
rnp->gpnum = rsp->gpnum;
|
|
rnp->completed = rsp->completed;
|
|
rnp->qsmask = 0;
|
|
rnp->qsmaskinit = 0;
|
|
rnp->grplo = j * cpustride;
|
|
rnp->grphi = (j + 1) * cpustride - 1;
|
|
if (rnp->grphi >= NR_CPUS)
|
|
rnp->grphi = NR_CPUS - 1;
|
|
if (i == 0) {
|
|
rnp->grpnum = 0;
|
|
rnp->grpmask = 0;
|
|
rnp->parent = NULL;
|
|
} else {
|
|
rnp->grpnum = j % rsp->levelspread[i - 1];
|
|
rnp->grpmask = 1UL << rnp->grpnum;
|
|
rnp->parent = rsp->level[i - 1] +
|
|
j / rsp->levelspread[i - 1];
|
|
}
|
|
rnp->level = i;
|
|
INIT_LIST_HEAD(&rnp->blkd_tasks);
|
|
}
|
|
}
|
|
|
|
rsp->rda = rda;
|
|
init_waitqueue_head(&rsp->gp_wq);
|
|
rnp = rsp->level[rcu_num_lvls - 1];
|
|
for_each_possible_cpu(i) {
|
|
while (i > rnp->grphi)
|
|
rnp++;
|
|
per_cpu_ptr(rsp->rda, i)->mynode = rnp;
|
|
rcu_boot_init_percpu_data(i, rsp);
|
|
}
|
|
list_add(&rsp->flavors, &rcu_struct_flavors);
|
|
}
|
|
|
|
/*
|
|
* Compute the rcu_node tree geometry from kernel parameters. This cannot
|
|
* replace the definitions in rcutree.h because those are needed to size
|
|
* the ->node array in the rcu_state structure.
|
|
*/
|
|
static void __init rcu_init_geometry(void)
|
|
{
|
|
int i;
|
|
int j;
|
|
int n = nr_cpu_ids;
|
|
int rcu_capacity[MAX_RCU_LVLS + 1];
|
|
|
|
/* If the compile-time values are accurate, just leave. */
|
|
if (rcu_fanout_leaf == CONFIG_RCU_FANOUT_LEAF &&
|
|
nr_cpu_ids == NR_CPUS)
|
|
return;
|
|
|
|
/*
|
|
* Compute number of nodes that can be handled an rcu_node tree
|
|
* with the given number of levels. Setting rcu_capacity[0] makes
|
|
* some of the arithmetic easier.
|
|
*/
|
|
rcu_capacity[0] = 1;
|
|
rcu_capacity[1] = rcu_fanout_leaf;
|
|
for (i = 2; i <= MAX_RCU_LVLS; i++)
|
|
rcu_capacity[i] = rcu_capacity[i - 1] * CONFIG_RCU_FANOUT;
|
|
|
|
/*
|
|
* The boot-time rcu_fanout_leaf parameter is only permitted
|
|
* to increase the leaf-level fanout, not decrease it. Of course,
|
|
* the leaf-level fanout cannot exceed the number of bits in
|
|
* the rcu_node masks. Finally, the tree must be able to accommodate
|
|
* the configured number of CPUs. Complain and fall back to the
|
|
* compile-time values if these limits are exceeded.
|
|
*/
|
|
if (rcu_fanout_leaf < CONFIG_RCU_FANOUT_LEAF ||
|
|
rcu_fanout_leaf > sizeof(unsigned long) * 8 ||
|
|
n > rcu_capacity[MAX_RCU_LVLS]) {
|
|
WARN_ON(1);
|
|
return;
|
|
}
|
|
|
|
/* Calculate the number of rcu_nodes at each level of the tree. */
|
|
for (i = 1; i <= MAX_RCU_LVLS; i++)
|
|
if (n <= rcu_capacity[i]) {
|
|
for (j = 0; j <= i; j++)
|
|
num_rcu_lvl[j] =
|
|
DIV_ROUND_UP(n, rcu_capacity[i - j]);
|
|
rcu_num_lvls = i;
|
|
for (j = i + 1; j <= MAX_RCU_LVLS; j++)
|
|
num_rcu_lvl[j] = 0;
|
|
break;
|
|
}
|
|
|
|
/* Calculate the total number of rcu_node structures. */
|
|
rcu_num_nodes = 0;
|
|
for (i = 0; i <= MAX_RCU_LVLS; i++)
|
|
rcu_num_nodes += num_rcu_lvl[i];
|
|
rcu_num_nodes -= n;
|
|
}
|
|
|
|
void __init rcu_init(void)
|
|
{
|
|
int cpu;
|
|
|
|
rcu_bootup_announce();
|
|
rcu_init_geometry();
|
|
rcu_init_one(&rcu_sched_state, &rcu_sched_data);
|
|
rcu_init_one(&rcu_bh_state, &rcu_bh_data);
|
|
__rcu_init_preempt();
|
|
rcu_init_nocb();
|
|
open_softirq(RCU_SOFTIRQ, rcu_process_callbacks);
|
|
|
|
/*
|
|
* We don't need protection against CPU-hotplug here because
|
|
* this is called early in boot, before either interrupts
|
|
* or the scheduler are operational.
|
|
*/
|
|
cpu_notifier(rcu_cpu_notify, 0);
|
|
for_each_online_cpu(cpu)
|
|
rcu_cpu_notify(NULL, CPU_UP_PREPARE, (void *)(long)cpu);
|
|
}
|
|
|
|
#include "rcutree_plugin.h"
|