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![Linus Torvalds](/assets/img/avatar_default.png)
* 'for-2.6.38' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/percpu: (30 commits) gameport: use this_cpu_read instead of lookup x86: udelay: Use this_cpu_read to avoid address calculation x86: Use this_cpu_inc_return for nmi counter x86: Replace uses of current_cpu_data with this_cpu ops x86: Use this_cpu_ops to optimize code vmstat: User per cpu atomics to avoid interrupt disable / enable irq_work: Use per cpu atomics instead of regular atomics cpuops: Use cmpxchg for xchg to avoid lock semantics x86: this_cpu_cmpxchg and this_cpu_xchg operations percpu: Generic this_cpu_cmpxchg() and this_cpu_xchg support percpu,x86: relocate this_cpu_add_return() and friends connector: Use this_cpu operations xen: Use this_cpu_inc_return taskstats: Use this_cpu_ops random: Use this_cpu_inc_return fs: Use this_cpu_inc_return in buffer.c highmem: Use this_cpu_xx_return() operations vmstat: Use this_cpu_inc_return for vm statistics x86: Support for this_cpu_add, sub, dec, inc_return percpu: Generic support for this_cpu_add, sub, dec, inc_return ... Fixed up conflicts: in arch/x86/kernel/{apic/nmi.c, apic/x2apic_uv_x.c, process.c} as per Tejun.
1984 lines
58 KiB
C
1984 lines
58 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 <asm/atomic.h>
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#include <linux/bitops.h>
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#include <linux/module.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 "rcutree.h"
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/* Data structures. */
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static struct lock_class_key rcu_node_class[NUM_RCU_LVLS];
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#define RCU_STATE_INITIALIZER(structname) { \
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.level = { &structname.node[0] }, \
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.levelcnt = { \
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NUM_RCU_LVL_0, /* root of hierarchy. */ \
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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, /* == MAX_RCU_LVLS */ \
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}, \
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.signaled = RCU_GP_IDLE, \
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.gpnum = -300, \
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.completed = -300, \
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.onofflock = __RAW_SPIN_LOCK_UNLOCKED(&structname.onofflock), \
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.fqslock = __RAW_SPIN_LOCK_UNLOCKED(&structname.fqslock), \
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.n_force_qs = 0, \
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.n_force_qs_ngp = 0, \
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.name = #structname, \
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}
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struct rcu_state rcu_sched_state = RCU_STATE_INITIALIZER(rcu_sched_state);
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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_state);
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DEFINE_PER_CPU(struct rcu_data, rcu_bh_data);
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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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* 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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*/
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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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rdp->passed_quiesc_completed = rdp->gpnum - 1;
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barrier();
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rdp->passed_quiesc = 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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rdp->passed_quiesc_completed = rdp->gpnum - 1;
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barrier();
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rdp->passed_quiesc = 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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*/
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void rcu_note_context_switch(int cpu)
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{
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rcu_sched_qs(cpu);
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rcu_preempt_note_context_switch(cpu);
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}
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#ifdef CONFIG_NO_HZ
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DEFINE_PER_CPU(struct rcu_dynticks, rcu_dynticks) = {
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.dynticks_nesting = 1,
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.dynticks = 1,
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};
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#endif /* #ifdef CONFIG_NO_HZ */
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static int blimit = 10; /* Maximum callbacks per softirq. */
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static int qhimark = 10000; /* If this many pending, ignore blimit. */
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static int qlowmark = 100; /* Once only this many pending, use blimit. */
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module_param(blimit, int, 0);
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module_param(qhimark, int, 0);
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module_param(qlowmark, int, 0);
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#ifdef CONFIG_RCU_CPU_STALL_DETECTOR
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int rcu_cpu_stall_suppress __read_mostly = RCU_CPU_STALL_SUPPRESS_INIT;
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module_param(rcu_cpu_stall_suppress, int, 0644);
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#endif /* #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */
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static void force_quiescent_state(struct rcu_state *rsp, int relaxed);
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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, 0);
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}
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EXPORT_SYMBOL_GPL(rcu_bh_force_quiescent_state);
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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, 0);
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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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}
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/*
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* Does the current CPU require a yet-as-unscheduled grace period?
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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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return *rdp->nxttail[RCU_DONE_TAIL] && !rcu_gp_in_progress(rsp);
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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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#ifdef CONFIG_SMP
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/*
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* If the specified CPU is offline, tell the caller that it is in
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* a quiescent state. Otherwise, whack it with a reschedule IPI.
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* Grace periods can end up waiting on an offline CPU when that
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* CPU is in the process of coming online -- it will be added to the
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* rcu_node bitmasks before it actually makes it online. The same thing
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* can happen while a CPU is in the process of coming online. Because this
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* race is quite rare, we check for it after detecting that the grace
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* period has been delayed rather than checking each and every CPU
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* each and every time we start a new grace period.
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*/
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static int rcu_implicit_offline_qs(struct rcu_data *rdp)
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{
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/*
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* If the CPU is offline, it is in a quiescent state. We can
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* trust its state not to change because interrupts are disabled.
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*/
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if (cpu_is_offline(rdp->cpu)) {
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rdp->offline_fqs++;
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return 1;
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}
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/* If preemptable RCU, no point in sending reschedule IPI. */
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if (rdp->preemptable)
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return 0;
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/* The CPU is online, so send it a reschedule IPI. */
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if (rdp->cpu != smp_processor_id())
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smp_send_reschedule(rdp->cpu);
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else
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set_need_resched();
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rdp->resched_ipi++;
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return 0;
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}
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#endif /* #ifdef CONFIG_SMP */
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#ifdef CONFIG_NO_HZ
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/**
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* rcu_enter_nohz - inform RCU that current CPU is entering nohz
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*
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* Enter nohz 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 nohz mode, a possibility
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* handled by rcu_irq_enter() and rcu_irq_exit()).
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*/
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void rcu_enter_nohz(void)
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{
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unsigned long flags;
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struct rcu_dynticks *rdtp;
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smp_mb(); /* CPUs seeing ++ must see prior RCU read-side crit sects */
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local_irq_save(flags);
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rdtp = &__get_cpu_var(rcu_dynticks);
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rdtp->dynticks++;
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rdtp->dynticks_nesting--;
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WARN_ON_ONCE(rdtp->dynticks & 0x1);
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local_irq_restore(flags);
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}
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/*
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* rcu_exit_nohz - inform RCU that current CPU is leaving nohz
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*
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* Exit nohz mode, in other words, -enter- the mode in which RCU
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* read-side critical sections normally occur.
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*/
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void rcu_exit_nohz(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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rdtp->dynticks++;
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rdtp->dynticks_nesting++;
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WARN_ON_ONCE(!(rdtp->dynticks & 0x1));
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local_irq_restore(flags);
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smp_mb(); /* CPUs seeing ++ must see later RCU read-side crit sects */
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}
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/**
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* rcu_nmi_enter - inform RCU of entry to NMI context
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*
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* If the CPU was idle with dynamic ticks active, and there is no
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* irq handler running, this updates rdtp->dynticks_nmi to let the
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* RCU grace-period handling know that the CPU is active.
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*/
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void rcu_nmi_enter(void)
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{
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struct rcu_dynticks *rdtp = &__get_cpu_var(rcu_dynticks);
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if (rdtp->dynticks & 0x1)
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return;
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rdtp->dynticks_nmi++;
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WARN_ON_ONCE(!(rdtp->dynticks_nmi & 0x1));
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smp_mb(); /* CPUs seeing ++ must see later RCU read-side crit sects */
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}
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/**
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* rcu_nmi_exit - inform RCU of exit from NMI context
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*
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* If the CPU was idle with dynamic ticks active, and there is no
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* irq handler running, this updates rdtp->dynticks_nmi to let the
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* RCU grace-period handling know that the CPU is no longer active.
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*/
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void rcu_nmi_exit(void)
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{
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struct rcu_dynticks *rdtp = &__get_cpu_var(rcu_dynticks);
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if (rdtp->dynticks & 0x1)
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return;
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smp_mb(); /* CPUs seeing ++ must see prior RCU read-side crit sects */
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rdtp->dynticks_nmi++;
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WARN_ON_ONCE(rdtp->dynticks_nmi & 0x1);
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}
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/**
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* rcu_irq_enter - inform RCU of entry to hard irq context
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*
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* If the CPU was idle with dynamic ticks active, this updates the
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* rdtp->dynticks to let the RCU handling know that the CPU is active.
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*/
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void rcu_irq_enter(void)
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{
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struct rcu_dynticks *rdtp = &__get_cpu_var(rcu_dynticks);
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if (rdtp->dynticks_nesting++)
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return;
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rdtp->dynticks++;
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WARN_ON_ONCE(!(rdtp->dynticks & 0x1));
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smp_mb(); /* CPUs seeing ++ must see later RCU read-side crit sects */
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}
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/**
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* rcu_irq_exit - inform RCU of exit from hard irq context
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*
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* If the CPU was idle with dynamic ticks active, update the rdp->dynticks
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* to put let the RCU handling be aware that the CPU is going back to idle
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* with no ticks.
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*/
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void rcu_irq_exit(void)
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{
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struct rcu_dynticks *rdtp = &__get_cpu_var(rcu_dynticks);
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if (--rdtp->dynticks_nesting)
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return;
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smp_mb(); /* CPUs seeing ++ must see prior RCU read-side crit sects */
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rdtp->dynticks++;
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WARN_ON_ONCE(rdtp->dynticks & 0x1);
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/* If the interrupt queued a callback, get out of dyntick mode. */
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if (__this_cpu_read(rcu_sched_data.nxtlist) ||
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__this_cpu_read(rcu_bh_data.nxtlist))
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set_need_resched();
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}
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#ifdef CONFIG_SMP
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/*
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* Snapshot the specified CPU's dynticks counter so that we can later
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* credit them with an implicit quiescent state. Return 1 if this CPU
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* is in dynticks idle mode, which is an extended quiescent state.
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*/
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static int dyntick_save_progress_counter(struct rcu_data *rdp)
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{
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int ret;
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int snap;
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int snap_nmi;
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snap = rdp->dynticks->dynticks;
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snap_nmi = rdp->dynticks->dynticks_nmi;
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smp_mb(); /* Order sampling of snap with end of grace period. */
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rdp->dynticks_snap = snap;
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rdp->dynticks_nmi_snap = snap_nmi;
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ret = ((snap & 0x1) == 0) && ((snap_nmi & 0x1) == 0);
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if (ret)
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rdp->dynticks_fqs++;
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return ret;
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}
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/*
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* Return true if the specified CPU has passed through a quiescent
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* state by virtue of being in or having passed through an dynticks
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* idle state since the last call to dyntick_save_progress_counter()
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* for this same CPU.
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*/
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static int rcu_implicit_dynticks_qs(struct rcu_data *rdp)
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{
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long curr;
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long curr_nmi;
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long snap;
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long snap_nmi;
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curr = rdp->dynticks->dynticks;
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snap = rdp->dynticks_snap;
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curr_nmi = rdp->dynticks->dynticks_nmi;
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snap_nmi = rdp->dynticks_nmi_snap;
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smp_mb(); /* force ordering with cpu entering/leaving dynticks. */
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/*
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* If the CPU passed through or entered a dynticks idle phase with
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* no active irq/NMI handlers, then we can safely pretend that the CPU
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* already acknowledged the request to pass through a quiescent
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* state. Either way, that CPU cannot possibly be in an RCU
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* read-side critical section that started before the beginning
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* of the current RCU grace period.
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*/
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if ((curr != snap || (curr & 0x1) == 0) &&
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(curr_nmi != snap_nmi || (curr_nmi & 0x1) == 0)) {
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rdp->dynticks_fqs++;
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return 1;
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}
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/* Go check for the CPU being offline. */
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return rcu_implicit_offline_qs(rdp);
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}
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#endif /* #ifdef CONFIG_SMP */
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#else /* #ifdef CONFIG_NO_HZ */
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#ifdef CONFIG_SMP
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static int dyntick_save_progress_counter(struct rcu_data *rdp)
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{
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return 0;
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}
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static int rcu_implicit_dynticks_qs(struct rcu_data *rdp)
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{
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return rcu_implicit_offline_qs(rdp);
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}
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#endif /* #ifdef CONFIG_SMP */
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#endif /* #else #ifdef CONFIG_NO_HZ */
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#ifdef CONFIG_RCU_CPU_STALL_DETECTOR
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int rcu_cpu_stall_suppress __read_mostly;
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static void record_gp_stall_check_time(struct rcu_state *rsp)
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{
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rsp->gp_start = jiffies;
|
|
rsp->jiffies_stall = jiffies + RCU_SECONDS_TILL_STALL_CHECK;
|
|
}
|
|
|
|
static void print_other_cpu_stall(struct rcu_state *rsp)
|
|
{
|
|
int cpu;
|
|
long delta;
|
|
unsigned long flags;
|
|
struct rcu_node *rnp = rcu_get_root(rsp);
|
|
|
|
/* 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 + RCU_SECONDS_TILL_STALL_RECHECK;
|
|
|
|
/*
|
|
* Now rat on any tasks that got kicked up to the root rcu_node
|
|
* due to CPU offlining.
|
|
*/
|
|
rcu_print_task_stall(rnp);
|
|
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);
|
|
rcu_for_each_leaf_node(rsp, rnp) {
|
|
raw_spin_lock_irqsave(&rnp->lock, flags);
|
|
rcu_print_task_stall(rnp);
|
|
raw_spin_unlock_irqrestore(&rnp->lock, flags);
|
|
if (rnp->qsmask == 0)
|
|
continue;
|
|
for (cpu = 0; cpu <= rnp->grphi - rnp->grplo; cpu++)
|
|
if (rnp->qsmask & (1UL << cpu))
|
|
printk(" %d", rnp->grplo + cpu);
|
|
}
|
|
printk("} (detected by %d, t=%ld jiffies)\n",
|
|
smp_processor_id(), (long)(jiffies - rsp->gp_start));
|
|
trigger_all_cpu_backtrace();
|
|
|
|
/* If so configured, complain about tasks blocking the grace period. */
|
|
|
|
rcu_print_detail_task_stall(rsp);
|
|
|
|
force_quiescent_state(rsp, 0); /* Kick them all. */
|
|
}
|
|
|
|
static void print_cpu_stall(struct rcu_state *rsp)
|
|
{
|
|
unsigned long flags;
|
|
struct rcu_node *rnp = rcu_get_root(rsp);
|
|
|
|
/*
|
|
* 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 detected stall on CPU %d (t=%lu jiffies)\n",
|
|
rsp->name, smp_processor_id(), jiffies - rsp->gp_start);
|
|
trigger_all_cpu_backtrace();
|
|
|
|
raw_spin_lock_irqsave(&rnp->lock, flags);
|
|
if (ULONG_CMP_GE(jiffies, rsp->jiffies_stall))
|
|
rsp->jiffies_stall =
|
|
jiffies + RCU_SECONDS_TILL_STALL_RECHECK;
|
|
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)
|
|
{
|
|
long delta;
|
|
struct rcu_node *rnp;
|
|
|
|
if (rcu_cpu_stall_suppress)
|
|
return;
|
|
delta = jiffies - ACCESS_ONCE(rsp->jiffies_stall);
|
|
rnp = rdp->mynode;
|
|
if ((ACCESS_ONCE(rnp->qsmask) & rdp->grpmask) && delta >= 0) {
|
|
|
|
/* We haven't checked in, so go dump stack. */
|
|
print_cpu_stall(rsp);
|
|
|
|
} else if (rcu_gp_in_progress(rsp) && delta >= RCU_STALL_RAT_DELAY) {
|
|
|
|
/* They had two time units to dump stack, so complain. */
|
|
print_other_cpu_stall(rsp);
|
|
}
|
|
}
|
|
|
|
static int rcu_panic(struct notifier_block *this, unsigned long ev, void *ptr)
|
|
{
|
|
rcu_cpu_stall_suppress = 1;
|
|
return NOTIFY_DONE;
|
|
}
|
|
|
|
/**
|
|
* 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)
|
|
{
|
|
rcu_sched_state.jiffies_stall = jiffies + ULONG_MAX / 2;
|
|
rcu_bh_state.jiffies_stall = jiffies + ULONG_MAX / 2;
|
|
rcu_preempt_stall_reset();
|
|
}
|
|
|
|
static struct notifier_block rcu_panic_block = {
|
|
.notifier_call = rcu_panic,
|
|
};
|
|
|
|
static void __init check_cpu_stall_init(void)
|
|
{
|
|
atomic_notifier_chain_register(&panic_notifier_list, &rcu_panic_block);
|
|
}
|
|
|
|
#else /* #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */
|
|
|
|
static void record_gp_stall_check_time(struct rcu_state *rsp)
|
|
{
|
|
}
|
|
|
|
static void check_cpu_stall(struct rcu_state *rsp, struct rcu_data *rdp)
|
|
{
|
|
}
|
|
|
|
void rcu_cpu_stall_reset(void)
|
|
{
|
|
}
|
|
|
|
static void __init check_cpu_stall_init(void)
|
|
{
|
|
}
|
|
|
|
#endif /* #else #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */
|
|
|
|
/*
|
|
* 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;
|
|
if (rnp->qsmask & rdp->grpmask) {
|
|
rdp->qs_pending = 1;
|
|
rdp->passed_quiesc = 0;
|
|
} else
|
|
rdp->qs_pending = 0;
|
|
}
|
|
}
|
|
|
|
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;
|
|
}
|
|
|
|
/*
|
|
* 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) {
|
|
|
|
/* Advance callbacks. No harm if list empty. */
|
|
rdp->nxttail[RCU_DONE_TAIL] = rdp->nxttail[RCU_WAIT_TAIL];
|
|
rdp->nxttail[RCU_WAIT_TAIL] = rdp->nxttail[RCU_NEXT_READY_TAIL];
|
|
rdp->nxttail[RCU_NEXT_READY_TAIL] = rdp->nxttail[RCU_NEXT_TAIL];
|
|
|
|
/* Remember that we saw this grace-period completion. */
|
|
rdp->completed = rnp->completed;
|
|
|
|
/*
|
|
* 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.
|
|
*/
|
|
if (ULONG_CMP_LT(rdp->gpnum, rdp->completed))
|
|
rdp->gpnum = rdp->completed;
|
|
|
|
/*
|
|
* 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);
|
|
|
|
/*
|
|
* Because this CPU just now started the new grace period, we know
|
|
* that all of its callbacks will be covered by this upcoming grace
|
|
* period, even the ones that were registered arbitrarily recently.
|
|
* Therefore, advance all outstanding callbacks to RCU_WAIT_TAIL.
|
|
*
|
|
* Other CPUs cannot be sure exactly when the grace period started.
|
|
* Therefore, their recently registered callbacks must pass through
|
|
* an additional RCU_NEXT_READY stage, so that they will be handled
|
|
* by the next RCU grace period.
|
|
*/
|
|
rdp->nxttail[RCU_NEXT_READY_TAIL] = rdp->nxttail[RCU_NEXT_TAIL];
|
|
rdp->nxttail[RCU_WAIT_TAIL] = rdp->nxttail[RCU_NEXT_TAIL];
|
|
|
|
/* Set state so that this CPU will detect the next quiescent state. */
|
|
__note_new_gpnum(rsp, rnp, rdp);
|
|
}
|
|
|
|
/*
|
|
* 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.
|
|
*/
|
|
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 (!cpu_needs_another_gp(rsp, rdp) || rsp->fqs_active) {
|
|
if (cpu_needs_another_gp(rsp, rdp))
|
|
rsp->fqs_need_gp = 1;
|
|
if (rnp->completed == rsp->completed) {
|
|
raw_spin_unlock_irqrestore(&rnp->lock, flags);
|
|
return;
|
|
}
|
|
raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */
|
|
|
|
/*
|
|
* 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.
|
|
*/
|
|
rcu_for_each_node_breadth_first(rsp, rnp) {
|
|
raw_spin_lock(&rnp->lock); /* irqs already disabled. */
|
|
rnp->completed = rsp->completed;
|
|
raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */
|
|
}
|
|
local_irq_restore(flags);
|
|
return;
|
|
}
|
|
|
|
/* Advance to a new grace period and initialize state. */
|
|
rsp->gpnum++;
|
|
WARN_ON_ONCE(rsp->signaled == RCU_GP_INIT);
|
|
rsp->signaled = RCU_GP_INIT; /* Hold off force_quiescent_state. */
|
|
rsp->jiffies_force_qs = jiffies + RCU_JIFFIES_TILL_FORCE_QS;
|
|
record_gp_stall_check_time(rsp);
|
|
|
|
/* Special-case the common single-level case. */
|
|
if (NUM_RCU_NODES == 1) {
|
|
rcu_preempt_check_blocked_tasks(rnp);
|
|
rnp->qsmask = rnp->qsmaskinit;
|
|
rnp->gpnum = rsp->gpnum;
|
|
rnp->completed = rsp->completed;
|
|
rsp->signaled = RCU_SIGNAL_INIT; /* force_quiescent_state OK. */
|
|
rcu_start_gp_per_cpu(rsp, rnp, rdp);
|
|
raw_spin_unlock_irqrestore(&rnp->lock, flags);
|
|
return;
|
|
}
|
|
|
|
raw_spin_unlock(&rnp->lock); /* leave irqs disabled. */
|
|
|
|
|
|
/* Exclude any concurrent CPU-hotplug operations. */
|
|
raw_spin_lock(&rsp->onofflock); /* irqs already disabled. */
|
|
|
|
/*
|
|
* 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. This
|
|
* operation relies on the layout of the hierarchy within the
|
|
* rsp->node[] array. Note that other CPUs will access only
|
|
* the leaves of the hierarchy, which still indicate 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.
|
|
*
|
|
* Note that the grace period cannot complete until we finish
|
|
* the initialization process, as there will be at least one
|
|
* qsmask bit set in the root node until that time, namely the
|
|
* one corresponding to this CPU, due to the fact that we have
|
|
* irqs disabled.
|
|
*/
|
|
rcu_for_each_node_breadth_first(rsp, rnp) {
|
|
raw_spin_lock(&rnp->lock); /* irqs already disabled. */
|
|
rcu_preempt_check_blocked_tasks(rnp);
|
|
rnp->qsmask = rnp->qsmaskinit;
|
|
rnp->gpnum = rsp->gpnum;
|
|
rnp->completed = rsp->completed;
|
|
if (rnp == rdp->mynode)
|
|
rcu_start_gp_per_cpu(rsp, rnp, rdp);
|
|
raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */
|
|
}
|
|
|
|
rnp = rcu_get_root(rsp);
|
|
raw_spin_lock(&rnp->lock); /* irqs already disabled. */
|
|
rsp->signaled = RCU_SIGNAL_INIT; /* force_quiescent_state now OK. */
|
|
raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */
|
|
raw_spin_unlock_irqrestore(&rsp->onofflock, flags);
|
|
}
|
|
|
|
/*
|
|
* 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));
|
|
rsp->completed = rsp->gpnum;
|
|
rsp->signaled = RCU_GP_IDLE;
|
|
rcu_start_gp(rsp, flags); /* releases root node's rnp->lock. */
|
|
}
|
|
|
|
/*
|
|
* 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;
|
|
if (rnp->qsmask != 0 || rcu_preempted_readers(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, long lastcomp)
|
|
{
|
|
unsigned long flags;
|
|
unsigned long mask;
|
|
struct rcu_node *rnp;
|
|
|
|
rnp = rdp->mynode;
|
|
raw_spin_lock_irqsave(&rnp->lock, flags);
|
|
if (lastcomp != rnp->completed) {
|
|
|
|
/*
|
|
* Someone beat us to it for this grace period, so leave.
|
|
* The race with GP start is resolved by the fact that we
|
|
* hold the leaf rcu_node lock, so that the per-CPU bits
|
|
* cannot yet be initialized -- so we would simply find our
|
|
* CPU's bit already cleared in rcu_report_qs_rnp() if this
|
|
* race occurred.
|
|
*/
|
|
rdp->passed_quiesc = 0; /* try again later! */
|
|
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.
|
|
*/
|
|
rdp->nxttail[RCU_NEXT_READY_TAIL] = rdp->nxttail[RCU_NEXT_TAIL];
|
|
|
|
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_quiesc)
|
|
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, rdp->passed_quiesc_completed);
|
|
}
|
|
|
|
#ifdef CONFIG_HOTPLUG_CPU
|
|
|
|
/*
|
|
* Move a dying CPU's RCU callbacks to online CPU's callback list.
|
|
* Synchronization is not required because this function executes
|
|
* in stop_machine() context.
|
|
*/
|
|
static void rcu_send_cbs_to_online(struct rcu_state *rsp)
|
|
{
|
|
int i;
|
|
/* current DYING CPU is cleared in the cpu_online_mask */
|
|
int receive_cpu = cpumask_any(cpu_online_mask);
|
|
struct rcu_data *rdp = this_cpu_ptr(rsp->rda);
|
|
struct rcu_data *receive_rdp = per_cpu_ptr(rsp->rda, receive_cpu);
|
|
|
|
if (rdp->nxtlist == NULL)
|
|
return; /* irqs disabled, so comparison is stable. */
|
|
|
|
*receive_rdp->nxttail[RCU_NEXT_TAIL] = rdp->nxtlist;
|
|
receive_rdp->nxttail[RCU_NEXT_TAIL] = rdp->nxttail[RCU_NEXT_TAIL];
|
|
receive_rdp->qlen += rdp->qlen;
|
|
receive_rdp->n_cbs_adopted += rdp->qlen;
|
|
rdp->n_cbs_orphaned += rdp->qlen;
|
|
|
|
rdp->nxtlist = NULL;
|
|
for (i = 0; i < RCU_NEXT_SIZE; i++)
|
|
rdp->nxttail[i] = &rdp->nxtlist;
|
|
rdp->qlen = 0;
|
|
}
|
|
|
|
/*
|
|
* Remove the outgoing CPU from the bitmasks in the rcu_node hierarchy
|
|
* and move all callbacks from the outgoing CPU to the current one.
|
|
*/
|
|
static void __rcu_offline_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;
|
|
|
|
/* Exclude any attempts to start a new grace period. */
|
|
raw_spin_lock_irqsave(&rsp->onofflock, flags);
|
|
|
|
/* Remove the outgoing CPU from the masks in the rcu_node hierarchy. */
|
|
rnp = rdp->mynode; /* this is the outgoing CPU's rnp. */
|
|
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 ->onofflock
|
|
* held leads to deadlock.
|
|
*/
|
|
raw_spin_unlock(&rsp->onofflock); /* 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);
|
|
}
|
|
|
|
/*
|
|
* Remove the specified CPU from the RCU hierarchy and move any pending
|
|
* callbacks that it might have to the current CPU. This code assumes
|
|
* that at least one CPU in the system will remain running at all times.
|
|
* Any attempt to offline -all- CPUs is likely to strand RCU callbacks.
|
|
*/
|
|
static void rcu_offline_cpu(int cpu)
|
|
{
|
|
__rcu_offline_cpu(cpu, &rcu_sched_state);
|
|
__rcu_offline_cpu(cpu, &rcu_bh_state);
|
|
rcu_preempt_offline_cpu(cpu);
|
|
}
|
|
|
|
#else /* #ifdef CONFIG_HOTPLUG_CPU */
|
|
|
|
static void rcu_send_cbs_to_online(struct rcu_state *rsp)
|
|
{
|
|
}
|
|
|
|
static void rcu_offline_cpu(int cpu)
|
|
{
|
|
}
|
|
|
|
#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;
|
|
int count;
|
|
|
|
/* If no callbacks are ready, just return.*/
|
|
if (!cpu_has_callbacks_ready_to_invoke(rdp))
|
|
return;
|
|
|
|
/*
|
|
* Extract the list of ready callbacks, disabling to prevent
|
|
* races with call_rcu() from interrupt handlers.
|
|
*/
|
|
local_irq_save(flags);
|
|
list = rdp->nxtlist;
|
|
rdp->nxtlist = *rdp->nxttail[RCU_DONE_TAIL];
|
|
*rdp->nxttail[RCU_DONE_TAIL] = NULL;
|
|
tail = rdp->nxttail[RCU_DONE_TAIL];
|
|
for (count = RCU_NEXT_SIZE - 1; count >= 0; count--)
|
|
if (rdp->nxttail[count] == rdp->nxttail[RCU_DONE_TAIL])
|
|
rdp->nxttail[count] = &rdp->nxtlist;
|
|
local_irq_restore(flags);
|
|
|
|
/* Invoke callbacks. */
|
|
count = 0;
|
|
while (list) {
|
|
next = list->next;
|
|
prefetch(next);
|
|
debug_rcu_head_unqueue(list);
|
|
list->func(list);
|
|
list = next;
|
|
if (++count >= rdp->blimit)
|
|
break;
|
|
}
|
|
|
|
local_irq_save(flags);
|
|
|
|
/* Update count, and requeue any remaining callbacks. */
|
|
rdp->qlen -= count;
|
|
rdp->n_cbs_invoked += count;
|
|
if (list != NULL) {
|
|
*tail = rdp->nxtlist;
|
|
rdp->nxtlist = list;
|
|
for (count = 0; count < RCU_NEXT_SIZE; count++)
|
|
if (&rdp->nxtlist == rdp->nxttail[count])
|
|
rdp->nxttail[count] = tail;
|
|
else
|
|
break;
|
|
}
|
|
|
|
/* 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;
|
|
|
|
local_irq_restore(flags);
|
|
|
|
/* Re-raise the RCU softirq if there are callbacks remaining. */
|
|
if (cpu_has_callbacks_ready_to_invoke(rdp))
|
|
raise_softirq(RCU_SOFTIRQ);
|
|
}
|
|
|
|
/*
|
|
* 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 the RCU softirq handler.
|
|
*
|
|
* This function must be called with hardirqs disabled. 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)
|
|
{
|
|
if (user ||
|
|
(idle_cpu(cpu) && rcu_scheduler_active &&
|
|
!in_softirq() && hardirq_count() <= (1 << HARDIRQ_SHIFT))) {
|
|
|
|
/*
|
|
* 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))
|
|
raise_softirq(RCU_SOFTIRQ);
|
|
}
|
|
|
|
#ifdef CONFIG_SMP
|
|
|
|
/*
|
|
* Scan the leaf rcu_node structures, processing dyntick state for any that
|
|
* have not yet encountered a quiescent state, using the function specified.
|
|
* 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) {
|
|
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) {
|
|
raw_spin_unlock_irqrestore(&rnp->lock, flags);
|
|
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);
|
|
}
|
|
}
|
|
|
|
/*
|
|
* 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, int relaxed)
|
|
{
|
|
unsigned long flags;
|
|
struct rcu_node *rnp = rcu_get_root(rsp);
|
|
|
|
if (!rcu_gp_in_progress(rsp))
|
|
return; /* No grace period in progress, nothing to force. */
|
|
if (!raw_spin_trylock_irqsave(&rsp->fqslock, flags)) {
|
|
rsp->n_force_qs_lh++; /* Inexact, can lose counts. Tough! */
|
|
return; /* Someone else is already on the job. */
|
|
}
|
|
if (relaxed && ULONG_CMP_GE(rsp->jiffies_force_qs, jiffies))
|
|
goto unlock_fqs_ret; /* no emergency and done recently. */
|
|
rsp->n_force_qs++;
|
|
raw_spin_lock(&rnp->lock); /* irqs already disabled */
|
|
rsp->jiffies_force_qs = jiffies + RCU_JIFFIES_TILL_FORCE_QS;
|
|
if(!rcu_gp_in_progress(rsp)) {
|
|
rsp->n_force_qs_ngp++;
|
|
raw_spin_unlock(&rnp->lock); /* irqs remain disabled */
|
|
goto unlock_fqs_ret; /* no GP in progress, time updated. */
|
|
}
|
|
rsp->fqs_active = 1;
|
|
switch (rsp->signaled) {
|
|
case RCU_GP_IDLE:
|
|
case RCU_GP_INIT:
|
|
|
|
break; /* grace period idle or initializing, ignore. */
|
|
|
|
case RCU_SAVE_DYNTICK:
|
|
if (RCU_SIGNAL_INIT != RCU_SAVE_DYNTICK)
|
|
break; /* So gcc recognizes the dead code. */
|
|
|
|
raw_spin_unlock(&rnp->lock); /* irqs remain disabled */
|
|
|
|
/* Record dyntick-idle state. */
|
|
force_qs_rnp(rsp, dyntick_save_progress_counter);
|
|
raw_spin_lock(&rnp->lock); /* irqs already disabled */
|
|
if (rcu_gp_in_progress(rsp))
|
|
rsp->signaled = RCU_FORCE_QS;
|
|
break;
|
|
|
|
case RCU_FORCE_QS:
|
|
|
|
/* Check dyntick-idle state, send IPI to laggarts. */
|
|
raw_spin_unlock(&rnp->lock); /* irqs remain disabled */
|
|
force_qs_rnp(rsp, rcu_implicit_dynticks_qs);
|
|
|
|
/* Leave state in case more forcing is required. */
|
|
|
|
raw_spin_lock(&rnp->lock); /* irqs already disabled */
|
|
break;
|
|
}
|
|
rsp->fqs_active = 0;
|
|
if (rsp->fqs_need_gp) {
|
|
raw_spin_unlock(&rsp->fqslock); /* irqs remain disabled */
|
|
rsp->fqs_need_gp = 0;
|
|
rcu_start_gp(rsp, flags); /* releases rnp->lock */
|
|
return;
|
|
}
|
|
raw_spin_unlock(&rnp->lock); /* irqs remain disabled */
|
|
unlock_fqs_ret:
|
|
raw_spin_unlock_irqrestore(&rsp->fqslock, flags);
|
|
}
|
|
|
|
#else /* #ifdef CONFIG_SMP */
|
|
|
|
static void force_quiescent_state(struct rcu_state *rsp, int relaxed)
|
|
{
|
|
set_need_resched();
|
|
}
|
|
|
|
#endif /* #else #ifdef CONFIG_SMP */
|
|
|
|
/*
|
|
* This does the RCU processing work from softirq context 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, struct rcu_data *rdp)
|
|
{
|
|
unsigned long flags;
|
|
|
|
WARN_ON_ONCE(rdp->beenonline == 0);
|
|
|
|
/*
|
|
* If an RCU GP has gone long enough, go check for dyntick
|
|
* idle CPUs and, if needed, send resched IPIs.
|
|
*/
|
|
if (ULONG_CMP_LT(ACCESS_ONCE(rsp->jiffies_force_qs), jiffies))
|
|
force_quiescent_state(rsp, 1);
|
|
|
|
/*
|
|
* Advance callbacks in response to end of earlier 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? */
|
|
if (cpu_needs_another_gp(rsp, rdp)) {
|
|
raw_spin_lock_irqsave(&rcu_get_root(rsp)->lock, flags);
|
|
rcu_start_gp(rsp, flags); /* releases above lock */
|
|
}
|
|
|
|
/* If there are callbacks ready, invoke them. */
|
|
rcu_do_batch(rsp, rdp);
|
|
}
|
|
|
|
/*
|
|
* Do softirq processing for the current CPU.
|
|
*/
|
|
static void rcu_process_callbacks(struct softirq_action *unused)
|
|
{
|
|
/*
|
|
* Memory references from any prior RCU read-side critical sections
|
|
* executed by the interrupted code must be seen before any RCU
|
|
* grace-period manipulations below.
|
|
*/
|
|
smp_mb(); /* See above block comment. */
|
|
|
|
__rcu_process_callbacks(&rcu_sched_state,
|
|
&__get_cpu_var(rcu_sched_data));
|
|
__rcu_process_callbacks(&rcu_bh_state, &__get_cpu_var(rcu_bh_data));
|
|
rcu_preempt_process_callbacks();
|
|
|
|
/*
|
|
* Memory references from any later RCU read-side critical sections
|
|
* executed by the interrupted code must be seen after any RCU
|
|
* grace-period manipulations above.
|
|
*/
|
|
smp_mb(); /* See above block comment. */
|
|
|
|
/* If we are last CPU on way to dyntick-idle mode, accelerate it. */
|
|
rcu_needs_cpu_flush();
|
|
}
|
|
|
|
static void
|
|
__call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu),
|
|
struct rcu_state *rsp)
|
|
{
|
|
unsigned long flags;
|
|
struct rcu_data *rdp;
|
|
|
|
debug_rcu_head_queue(head);
|
|
head->func = func;
|
|
head->next = NULL;
|
|
|
|
smp_mb(); /* Ensure RCU update seen before callback registry. */
|
|
|
|
/*
|
|
* 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. */
|
|
*rdp->nxttail[RCU_NEXT_TAIL] = head;
|
|
rdp->nxttail[RCU_NEXT_TAIL] = &head->next;
|
|
|
|
/*
|
|
* 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, 0);
|
|
rdp->n_force_qs_snap = rsp->n_force_qs;
|
|
rdp->qlen_last_fqs_check = rdp->qlen;
|
|
}
|
|
} else if (ULONG_CMP_LT(ACCESS_ONCE(rsp->jiffies_force_qs), jiffies))
|
|
force_quiescent_state(rsp, 1);
|
|
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);
|
|
}
|
|
EXPORT_SYMBOL_GPL(call_rcu_sched);
|
|
|
|
/*
|
|
* Queue an RCU 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);
|
|
}
|
|
EXPORT_SYMBOL_GPL(call_rcu_bh);
|
|
|
|
/**
|
|
* 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
|
|
* 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.
|
|
*
|
|
* 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)
|
|
{
|
|
struct rcu_synchronize rcu;
|
|
|
|
if (rcu_blocking_is_gp())
|
|
return;
|
|
|
|
init_rcu_head_on_stack(&rcu.head);
|
|
init_completion(&rcu.completion);
|
|
/* Will wake me after RCU finished. */
|
|
call_rcu_sched(&rcu.head, wakeme_after_rcu);
|
|
/* Wait for it. */
|
|
wait_for_completion(&rcu.completion);
|
|
destroy_rcu_head_on_stack(&rcu.head);
|
|
}
|
|
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.
|
|
*/
|
|
void synchronize_rcu_bh(void)
|
|
{
|
|
struct rcu_synchronize rcu;
|
|
|
|
if (rcu_blocking_is_gp())
|
|
return;
|
|
|
|
init_rcu_head_on_stack(&rcu.head);
|
|
init_completion(&rcu.completion);
|
|
/* Will wake me after RCU finished. */
|
|
call_rcu_bh(&rcu.head, wakeme_after_rcu);
|
|
/* Wait for it. */
|
|
wait_for_completion(&rcu.completion);
|
|
destroy_rcu_head_on_stack(&rcu.head);
|
|
}
|
|
EXPORT_SYMBOL_GPL(synchronize_rcu_bh);
|
|
|
|
/*
|
|
* 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 (rdp->qs_pending && !rdp->passed_quiesc) {
|
|
|
|
/*
|
|
* If force_quiescent_state() coming soon and this CPU
|
|
* needs a quiescent state, and this is either RCU-sched
|
|
* or RCU-bh, force a local reschedule.
|
|
*/
|
|
rdp->n_rp_qs_pending++;
|
|
if (!rdp->preemptable &&
|
|
ULONG_CMP_LT(ACCESS_ONCE(rsp->jiffies_force_qs) - 1,
|
|
jiffies))
|
|
set_need_resched();
|
|
} else if (rdp->qs_pending && rdp->passed_quiesc) {
|
|
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;
|
|
}
|
|
|
|
/* Has an RCU GP gone long enough to send resched IPIs &c? */
|
|
if (rcu_gp_in_progress(rsp) &&
|
|
ULONG_CMP_LT(ACCESS_ONCE(rsp->jiffies_force_qs), jiffies)) {
|
|
rdp->n_rp_need_fqs++;
|
|
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)
|
|
{
|
|
return __rcu_pending(&rcu_sched_state, &per_cpu(rcu_sched_data, cpu)) ||
|
|
__rcu_pending(&rcu_bh_state, &per_cpu(rcu_bh_data, cpu)) ||
|
|
rcu_preempt_pending(cpu);
|
|
}
|
|
|
|
/*
|
|
* 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_needs_cpu_quick_check(int cpu)
|
|
{
|
|
/* RCU callbacks either ready or pending? */
|
|
return per_cpu(rcu_sched_data, cpu).nxtlist ||
|
|
per_cpu(rcu_bh_data, cpu).nxtlist ||
|
|
rcu_preempt_needs_cpu(cpu);
|
|
}
|
|
|
|
static DEFINE_PER_CPU(struct rcu_head, rcu_barrier_head) = {NULL};
|
|
static atomic_t rcu_barrier_cpu_count;
|
|
static DEFINE_MUTEX(rcu_barrier_mutex);
|
|
static struct completion rcu_barrier_completion;
|
|
|
|
static void rcu_barrier_callback(struct rcu_head *notused)
|
|
{
|
|
if (atomic_dec_and_test(&rcu_barrier_cpu_count))
|
|
complete(&rcu_barrier_completion);
|
|
}
|
|
|
|
/*
|
|
* Called with preemption disabled, and from cross-cpu IRQ context.
|
|
*/
|
|
static void rcu_barrier_func(void *type)
|
|
{
|
|
int cpu = smp_processor_id();
|
|
struct rcu_head *head = &per_cpu(rcu_barrier_head, cpu);
|
|
void (*call_rcu_func)(struct rcu_head *head,
|
|
void (*func)(struct rcu_head *head));
|
|
|
|
atomic_inc(&rcu_barrier_cpu_count);
|
|
call_rcu_func = type;
|
|
call_rcu_func(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,
|
|
void (*call_rcu_func)(struct rcu_head *head,
|
|
void (*func)(struct rcu_head *head)))
|
|
{
|
|
BUG_ON(in_interrupt());
|
|
/* Take mutex to serialize concurrent rcu_barrier() requests. */
|
|
mutex_lock(&rcu_barrier_mutex);
|
|
init_completion(&rcu_barrier_completion);
|
|
/*
|
|
* Initialize rcu_barrier_cpu_count to 1, then invoke
|
|
* rcu_barrier_func() on each CPU, so that each CPU also has
|
|
* incremented rcu_barrier_cpu_count. Only then is it safe to
|
|
* decrement rcu_barrier_cpu_count -- otherwise the first CPU
|
|
* might complete its grace period before all of the other CPUs
|
|
* did their increment, causing this function to return too
|
|
* early. Note that on_each_cpu() disables irqs, which prevents
|
|
* any CPUs from coming online or going offline until each online
|
|
* CPU has queued its RCU-barrier callback.
|
|
*/
|
|
atomic_set(&rcu_barrier_cpu_count, 1);
|
|
on_each_cpu(rcu_barrier_func, (void *)call_rcu_func, 1);
|
|
if (atomic_dec_and_test(&rcu_barrier_cpu_count))
|
|
complete(&rcu_barrier_completion);
|
|
wait_for_completion(&rcu_barrier_completion);
|
|
mutex_unlock(&rcu_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, call_rcu_bh);
|
|
}
|
|
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, call_rcu_sched);
|
|
}
|
|
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;
|
|
int i;
|
|
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);
|
|
rdp->nxtlist = NULL;
|
|
for (i = 0; i < RCU_NEXT_SIZE; i++)
|
|
rdp->nxttail[i] = &rdp->nxtlist;
|
|
rdp->qlen = 0;
|
|
#ifdef CONFIG_NO_HZ
|
|
rdp->dynticks = &per_cpu(rcu_dynticks, cpu);
|
|
#endif /* #ifdef CONFIG_NO_HZ */
|
|
rdp->cpu = cpu;
|
|
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 preemptable)
|
|
{
|
|
unsigned long flags;
|
|
unsigned long mask;
|
|
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->passed_quiesc = 0; /* We could be racing with new GP, */
|
|
rdp->qs_pending = 1; /* so set up to respond to current GP. */
|
|
rdp->beenonline = 1; /* We have now been online. */
|
|
rdp->preemptable = preemptable;
|
|
rdp->qlen_last_fqs_check = 0;
|
|
rdp->n_force_qs_snap = rsp->n_force_qs;
|
|
rdp->blimit = blimit;
|
|
raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */
|
|
|
|
/*
|
|
* A new grace period might start here. If so, we won't be part
|
|
* of it, but that is OK, as we are currently in a quiescent state.
|
|
*/
|
|
|
|
/* Exclude any attempts to start a new GP on large systems. */
|
|
raw_spin_lock(&rsp->onofflock); /* irqs already 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) {
|
|
rdp->gpnum = rnp->completed; /* if GP in progress... */
|
|
rdp->completed = rnp->completed;
|
|
rdp->passed_quiesc_completed = rnp->completed - 1;
|
|
}
|
|
raw_spin_unlock(&rnp->lock); /* irqs already disabled. */
|
|
rnp = rnp->parent;
|
|
} while (rnp != NULL && !(rnp->qsmaskinit & mask));
|
|
|
|
raw_spin_unlock_irqrestore(&rsp->onofflock, flags);
|
|
}
|
|
|
|
static void __cpuinit rcu_online_cpu(int cpu)
|
|
{
|
|
rcu_init_percpu_data(cpu, &rcu_sched_state, 0);
|
|
rcu_init_percpu_data(cpu, &rcu_bh_state, 0);
|
|
rcu_preempt_init_percpu_data(cpu);
|
|
}
|
|
|
|
/*
|
|
* 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;
|
|
|
|
switch (action) {
|
|
case CPU_UP_PREPARE:
|
|
case CPU_UP_PREPARE_FROZEN:
|
|
rcu_online_cpu(cpu);
|
|
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.
|
|
*/
|
|
rcu_send_cbs_to_online(&rcu_bh_state);
|
|
rcu_send_cbs_to_online(&rcu_sched_state);
|
|
rcu_preempt_send_cbs_to_online();
|
|
break;
|
|
case CPU_DEAD:
|
|
case CPU_DEAD_FROZEN:
|
|
case CPU_UP_CANCELED:
|
|
case CPU_UP_CANCELED_FROZEN:
|
|
rcu_offline_cpu(cpu);
|
|
break;
|
|
default:
|
|
break;
|
|
}
|
|
return NOTIFY_OK;
|
|
}
|
|
|
|
/*
|
|
* 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 = NUM_RCU_LVLS - 1; i > 0; i--)
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|
rsp->levelspread[i] = CONFIG_RCU_FANOUT;
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|
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_CPUS;
|
|
for (i = NUM_RCU_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_level_0",
|
|
"rcu_node_level_1",
|
|
"rcu_node_level_2",
|
|
"rcu_node_level_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! */
|
|
|
|
/* Initialize the level-tracking arrays. */
|
|
|
|
for (i = 1; i < NUM_RCU_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 = NUM_RCU_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]);
|
|
rnp->gpnum = 0;
|
|
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->blocked_tasks[0]);
|
|
INIT_LIST_HEAD(&rnp->blocked_tasks[1]);
|
|
INIT_LIST_HEAD(&rnp->blocked_tasks[2]);
|
|
INIT_LIST_HEAD(&rnp->blocked_tasks[3]);
|
|
}
|
|
}
|
|
|
|
rsp->rda = rda;
|
|
rnp = rsp->level[NUM_RCU_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);
|
|
}
|
|
}
|
|
|
|
void __init rcu_init(void)
|
|
{
|
|
int cpu;
|
|
|
|
rcu_bootup_announce();
|
|
rcu_init_one(&rcu_sched_state, &rcu_sched_data);
|
|
rcu_init_one(&rcu_bh_state, &rcu_bh_data);
|
|
__rcu_init_preempt();
|
|
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);
|
|
check_cpu_stall_init();
|
|
}
|
|
|
|
#include "rcutree_plugin.h"
|