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![Ingo Molnar](/assets/img/avatar_default.png)
Impact: build fix for all non-x86 architectures We want to remove percpu.h from rcuclassic.h/rcutree.h (for upcoming kmemtrace changes) but that would break the DECLARE_PER_CPU based declarations in these files. Move the quiescent counter management functions to their respective RCU implementation .c files - they were slightly above the inlining limit anyway. Cc: Pekka Enberg <penberg@cs.helsinki.fi> Cc: Eduard - Gabriel Munteanu <eduard.munteanu@linux360.ro> Cc: paulmck@linux.vnet.ibm.com LKML-Reference: <1237898630.25315.83.camel@penberg-laptop> Signed-off-by: Ingo Molnar <mingo@elte.hu>
807 lines
22 KiB
C
807 lines
22 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, 2001
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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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*
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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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* Papers:
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* http://www.rdrop.com/users/paulmck/paper/rclockpdcsproof.pdf
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* http://lse.sourceforge.net/locking/rclock_OLS.2001.05.01c.sc.pdf (OLS2001)
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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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*/
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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 <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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#ifdef CONFIG_DEBUG_LOCK_ALLOC
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static struct lock_class_key rcu_lock_key;
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struct lockdep_map rcu_lock_map =
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STATIC_LOCKDEP_MAP_INIT("rcu_read_lock", &rcu_lock_key);
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EXPORT_SYMBOL_GPL(rcu_lock_map);
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#endif
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/* Definition for rcupdate control block. */
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static struct rcu_ctrlblk rcu_ctrlblk = {
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.cur = -300,
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.completed = -300,
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.pending = -300,
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.lock = __SPIN_LOCK_UNLOCKED(&rcu_ctrlblk.lock),
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.cpumask = CPU_BITS_NONE,
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};
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static struct rcu_ctrlblk rcu_bh_ctrlblk = {
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.cur = -300,
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.completed = -300,
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.pending = -300,
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.lock = __SPIN_LOCK_UNLOCKED(&rcu_bh_ctrlblk.lock),
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.cpumask = CPU_BITS_NONE,
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};
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static DEFINE_PER_CPU(struct rcu_data, rcu_data);
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static DEFINE_PER_CPU(struct rcu_data, rcu_bh_data);
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/*
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* Increment the quiescent state counter.
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* The counter is a bit degenerated: 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. Thus just a flag.
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*/
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void rcu_qsctr_inc(int cpu)
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{
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struct rcu_data *rdp = &per_cpu(rcu_data, cpu);
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rdp->passed_quiesc = 1;
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}
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void rcu_bh_qsctr_inc(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 = 1;
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}
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static int blimit = 10;
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static int qhimark = 10000;
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static int qlowmark = 100;
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#ifdef CONFIG_SMP
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static void force_quiescent_state(struct rcu_data *rdp,
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struct rcu_ctrlblk *rcp)
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{
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int cpu;
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unsigned long flags;
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set_need_resched();
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spin_lock_irqsave(&rcp->lock, flags);
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if (unlikely(!rcp->signaled)) {
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rcp->signaled = 1;
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/*
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* Don't send IPI to itself. With irqs disabled,
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* rdp->cpu is the current cpu.
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*
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* cpu_online_mask is updated by the _cpu_down()
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* using __stop_machine(). Since we're in irqs disabled
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* section, __stop_machine() is not exectuting, hence
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* the cpu_online_mask is stable.
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*
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* However, a cpu might have been offlined _just_ before
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* we disabled irqs while entering here.
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* And rcu subsystem might not yet have handled the CPU_DEAD
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* notification, leading to the offlined cpu's bit
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* being set in the rcp->cpumask.
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*
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* Hence cpumask = (rcp->cpumask & cpu_online_mask) to prevent
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* sending smp_reschedule() to an offlined CPU.
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*/
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for_each_cpu_and(cpu,
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to_cpumask(rcp->cpumask), cpu_online_mask) {
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if (cpu != rdp->cpu)
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smp_send_reschedule(cpu);
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}
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}
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spin_unlock_irqrestore(&rcp->lock, flags);
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}
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#else
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static inline void force_quiescent_state(struct rcu_data *rdp,
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struct rcu_ctrlblk *rcp)
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{
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set_need_resched();
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}
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#endif
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static void __call_rcu(struct rcu_head *head, struct rcu_ctrlblk *rcp,
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struct rcu_data *rdp)
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{
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long batch;
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head->next = NULL;
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smp_mb(); /* Read of rcu->cur must happen after any change by caller. */
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/*
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* Determine the batch number of this callback.
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*
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* Using ACCESS_ONCE to avoid the following error when gcc eliminates
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* local variable "batch" and emits codes like this:
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* 1) rdp->batch = rcp->cur + 1 # gets old value
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* ......
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* 2)rcu_batch_after(rcp->cur + 1, rdp->batch) # gets new value
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* then [*nxttail[0], *nxttail[1]) may contain callbacks
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* that batch# = rdp->batch, see the comment of struct rcu_data.
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*/
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batch = ACCESS_ONCE(rcp->cur) + 1;
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if (rdp->nxtlist && rcu_batch_after(batch, rdp->batch)) {
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/* process callbacks */
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rdp->nxttail[0] = rdp->nxttail[1];
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rdp->nxttail[1] = rdp->nxttail[2];
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if (rcu_batch_after(batch - 1, rdp->batch))
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rdp->nxttail[0] = rdp->nxttail[2];
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}
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rdp->batch = batch;
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*rdp->nxttail[2] = head;
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rdp->nxttail[2] = &head->next;
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if (unlikely(++rdp->qlen > qhimark)) {
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rdp->blimit = INT_MAX;
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force_quiescent_state(rdp, &rcu_ctrlblk);
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}
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}
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#ifdef CONFIG_RCU_CPU_STALL_DETECTOR
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static void record_gp_stall_check_time(struct rcu_ctrlblk *rcp)
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{
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rcp->gp_start = jiffies;
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rcp->jiffies_stall = jiffies + RCU_SECONDS_TILL_STALL_CHECK;
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}
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static void print_other_cpu_stall(struct rcu_ctrlblk *rcp)
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{
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int cpu;
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long delta;
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unsigned long flags;
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/* Only let one CPU complain about others per time interval. */
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spin_lock_irqsave(&rcp->lock, flags);
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delta = jiffies - rcp->jiffies_stall;
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if (delta < 2 || rcp->cur != rcp->completed) {
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spin_unlock_irqrestore(&rcp->lock, flags);
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return;
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}
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rcp->jiffies_stall = jiffies + RCU_SECONDS_TILL_STALL_RECHECK;
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spin_unlock_irqrestore(&rcp->lock, flags);
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/* OK, time to rat on our buddy... */
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printk(KERN_ERR "INFO: RCU detected CPU stalls:");
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for_each_possible_cpu(cpu) {
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if (cpumask_test_cpu(cpu, to_cpumask(rcp->cpumask)))
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printk(" %d", cpu);
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}
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printk(" (detected by %d, t=%ld jiffies)\n",
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smp_processor_id(), (long)(jiffies - rcp->gp_start));
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}
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static void print_cpu_stall(struct rcu_ctrlblk *rcp)
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{
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unsigned long flags;
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printk(KERN_ERR "INFO: RCU detected CPU %d stall (t=%lu/%lu jiffies)\n",
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smp_processor_id(), jiffies,
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jiffies - rcp->gp_start);
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dump_stack();
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spin_lock_irqsave(&rcp->lock, flags);
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if ((long)(jiffies - rcp->jiffies_stall) >= 0)
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rcp->jiffies_stall =
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jiffies + RCU_SECONDS_TILL_STALL_RECHECK;
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spin_unlock_irqrestore(&rcp->lock, flags);
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set_need_resched(); /* kick ourselves to get things going. */
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}
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static void check_cpu_stall(struct rcu_ctrlblk *rcp)
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{
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long delta;
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delta = jiffies - rcp->jiffies_stall;
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if (cpumask_test_cpu(smp_processor_id(), to_cpumask(rcp->cpumask)) &&
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delta >= 0) {
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/* We haven't checked in, so go dump stack. */
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print_cpu_stall(rcp);
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} else if (rcp->cur != rcp->completed && delta >= 2) {
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/* They had two seconds to dump stack, so complain. */
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print_other_cpu_stall(rcp);
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}
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}
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#else /* #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */
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static void record_gp_stall_check_time(struct rcu_ctrlblk *rcp)
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{
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}
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static inline void check_cpu_stall(struct rcu_ctrlblk *rcp)
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{
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}
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#endif /* #else #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */
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/**
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* call_rcu - Queue an RCU callback for invocation after a grace period.
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* @head: structure to be used for queueing the RCU updates.
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* @func: actual update function to be invoked after the grace period
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*
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* The update function will be invoked some time after a full grace
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* period elapses, in other words after all currently executing RCU
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* read-side critical sections have completed. RCU read-side critical
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* sections are delimited by rcu_read_lock() and rcu_read_unlock(),
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* and may be nested.
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*/
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void call_rcu(struct rcu_head *head,
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void (*func)(struct rcu_head *rcu))
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{
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unsigned long flags;
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head->func = func;
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local_irq_save(flags);
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__call_rcu(head, &rcu_ctrlblk, &__get_cpu_var(rcu_data));
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local_irq_restore(flags);
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}
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EXPORT_SYMBOL_GPL(call_rcu);
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/**
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* call_rcu_bh - Queue an RCU for invocation after a quicker grace period.
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* @head: structure to be used for queueing the RCU updates.
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* @func: actual update function to be invoked after the grace period
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*
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* The update function will be invoked some time after a full grace
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* period elapses, in other words after all currently executing RCU
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* read-side critical sections have completed. call_rcu_bh() assumes
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* that the read-side critical sections end on completion of a softirq
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* handler. This means that read-side critical sections in process
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* context must not be interrupted by softirqs. This interface is to be
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* used when most of the read-side critical sections are in softirq context.
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* RCU read-side critical sections are delimited by rcu_read_lock() and
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* rcu_read_unlock(), * if in interrupt context or rcu_read_lock_bh()
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* and rcu_read_unlock_bh(), if in process context. These may be nested.
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*/
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void call_rcu_bh(struct rcu_head *head,
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void (*func)(struct rcu_head *rcu))
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{
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unsigned long flags;
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head->func = func;
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local_irq_save(flags);
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__call_rcu(head, &rcu_bh_ctrlblk, &__get_cpu_var(rcu_bh_data));
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local_irq_restore(flags);
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}
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EXPORT_SYMBOL_GPL(call_rcu_bh);
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/*
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* Return the number of RCU batches processed thus far. Useful
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* for debug and statistics.
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*/
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long rcu_batches_completed(void)
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{
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return rcu_ctrlblk.completed;
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}
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EXPORT_SYMBOL_GPL(rcu_batches_completed);
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/*
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* Return the number of RCU batches processed thus far. Useful
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* for debug and statistics.
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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_ctrlblk.completed;
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}
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EXPORT_SYMBOL_GPL(rcu_batches_completed_bh);
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/* Raises the softirq for processing rcu_callbacks. */
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static inline void raise_rcu_softirq(void)
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{
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raise_softirq(RCU_SOFTIRQ);
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}
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/*
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* Invoke the completed RCU callbacks. They are expected to be in
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* a per-cpu list.
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*/
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static void rcu_do_batch(struct rcu_data *rdp)
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{
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unsigned long flags;
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struct rcu_head *next, *list;
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int count = 0;
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list = rdp->donelist;
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while (list) {
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next = list->next;
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prefetch(next);
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list->func(list);
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list = next;
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if (++count >= rdp->blimit)
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break;
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}
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rdp->donelist = list;
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local_irq_save(flags);
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rdp->qlen -= count;
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local_irq_restore(flags);
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if (rdp->blimit == INT_MAX && rdp->qlen <= qlowmark)
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rdp->blimit = blimit;
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if (!rdp->donelist)
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rdp->donetail = &rdp->donelist;
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else
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raise_rcu_softirq();
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}
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/*
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* Grace period handling:
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* The grace period handling consists out of two steps:
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* - A new grace period is started.
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* This is done by rcu_start_batch. The start is not broadcasted to
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* all cpus, they must pick this up by comparing rcp->cur with
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* rdp->quiescbatch. All cpus are recorded in the
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* rcu_ctrlblk.cpumask bitmap.
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* - All cpus must go through a quiescent state.
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* Since the start of the grace period is not broadcasted, at least two
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* calls to rcu_check_quiescent_state are required:
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* The first call just notices that a new grace period is running. The
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* following calls check if there was a quiescent state since the beginning
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* of the grace period. If so, it updates rcu_ctrlblk.cpumask. If
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* the bitmap is empty, then the grace period is completed.
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* rcu_check_quiescent_state calls rcu_start_batch(0) to start the next grace
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* period (if necessary).
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*/
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/*
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* Register a new batch of callbacks, and start it up if there is currently no
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* active batch and the batch to be registered has not already occurred.
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* Caller must hold rcu_ctrlblk.lock.
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*/
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static void rcu_start_batch(struct rcu_ctrlblk *rcp)
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{
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if (rcp->cur != rcp->pending &&
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rcp->completed == rcp->cur) {
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rcp->cur++;
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record_gp_stall_check_time(rcp);
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/*
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* Accessing nohz_cpu_mask before incrementing rcp->cur needs a
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* Barrier Otherwise it can cause tickless idle CPUs to be
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* included in rcp->cpumask, which will extend graceperiods
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* unnecessarily.
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*/
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smp_mb();
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cpumask_andnot(to_cpumask(rcp->cpumask),
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cpu_online_mask, nohz_cpu_mask);
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rcp->signaled = 0;
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}
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}
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/*
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* cpu went through a quiescent state since the beginning of the grace period.
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* Clear it from the cpu mask and complete the grace period if it was the last
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* cpu. Start another grace period if someone has further entries pending
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*/
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static void cpu_quiet(int cpu, struct rcu_ctrlblk *rcp)
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{
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cpumask_clear_cpu(cpu, to_cpumask(rcp->cpumask));
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if (cpumask_empty(to_cpumask(rcp->cpumask))) {
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/* batch completed ! */
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rcp->completed = rcp->cur;
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rcu_start_batch(rcp);
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}
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}
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/*
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* Check if the cpu has gone through a quiescent state (say context
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* switch). If so and if it already hasn't done so in this RCU
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* quiescent cycle, then indicate that it has done so.
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*/
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static void rcu_check_quiescent_state(struct rcu_ctrlblk *rcp,
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struct rcu_data *rdp)
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{
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unsigned long flags;
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if (rdp->quiescbatch != rcp->cur) {
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/* start new grace period: */
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rdp->qs_pending = 1;
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rdp->passed_quiesc = 0;
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rdp->quiescbatch = rcp->cur;
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return;
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}
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/* Grace period already completed for this cpu?
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* qs_pending is checked instead of the actual bitmap to avoid
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* cacheline trashing.
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*/
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if (!rdp->qs_pending)
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return;
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/*
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* Was there a quiescent state since the beginning of the grace
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* period? If no, then exit and wait for the next call.
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*/
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if (!rdp->passed_quiesc)
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return;
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rdp->qs_pending = 0;
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spin_lock_irqsave(&rcp->lock, flags);
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/*
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* rdp->quiescbatch/rcp->cur and the cpu bitmap can come out of sync
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* during cpu startup. Ignore the quiescent state.
|
|
*/
|
|
if (likely(rdp->quiescbatch == rcp->cur))
|
|
cpu_quiet(rdp->cpu, rcp);
|
|
|
|
spin_unlock_irqrestore(&rcp->lock, flags);
|
|
}
|
|
|
|
|
|
#ifdef CONFIG_HOTPLUG_CPU
|
|
|
|
/* warning! helper for rcu_offline_cpu. do not use elsewhere without reviewing
|
|
* locking requirements, the list it's pulling from has to belong to a cpu
|
|
* which is dead and hence not processing interrupts.
|
|
*/
|
|
static void rcu_move_batch(struct rcu_data *this_rdp, struct rcu_head *list,
|
|
struct rcu_head **tail, long batch)
|
|
{
|
|
unsigned long flags;
|
|
|
|
if (list) {
|
|
local_irq_save(flags);
|
|
this_rdp->batch = batch;
|
|
*this_rdp->nxttail[2] = list;
|
|
this_rdp->nxttail[2] = tail;
|
|
local_irq_restore(flags);
|
|
}
|
|
}
|
|
|
|
static void __rcu_offline_cpu(struct rcu_data *this_rdp,
|
|
struct rcu_ctrlblk *rcp, struct rcu_data *rdp)
|
|
{
|
|
unsigned long flags;
|
|
|
|
/*
|
|
* if the cpu going offline owns the grace period
|
|
* we can block indefinitely waiting for it, so flush
|
|
* it here
|
|
*/
|
|
spin_lock_irqsave(&rcp->lock, flags);
|
|
if (rcp->cur != rcp->completed)
|
|
cpu_quiet(rdp->cpu, rcp);
|
|
rcu_move_batch(this_rdp, rdp->donelist, rdp->donetail, rcp->cur + 1);
|
|
rcu_move_batch(this_rdp, rdp->nxtlist, rdp->nxttail[2], rcp->cur + 1);
|
|
spin_unlock(&rcp->lock);
|
|
|
|
this_rdp->qlen += rdp->qlen;
|
|
local_irq_restore(flags);
|
|
}
|
|
|
|
static void rcu_offline_cpu(int cpu)
|
|
{
|
|
struct rcu_data *this_rdp = &get_cpu_var(rcu_data);
|
|
struct rcu_data *this_bh_rdp = &get_cpu_var(rcu_bh_data);
|
|
|
|
__rcu_offline_cpu(this_rdp, &rcu_ctrlblk,
|
|
&per_cpu(rcu_data, cpu));
|
|
__rcu_offline_cpu(this_bh_rdp, &rcu_bh_ctrlblk,
|
|
&per_cpu(rcu_bh_data, cpu));
|
|
put_cpu_var(rcu_data);
|
|
put_cpu_var(rcu_bh_data);
|
|
}
|
|
|
|
#else
|
|
|
|
static void rcu_offline_cpu(int cpu)
|
|
{
|
|
}
|
|
|
|
#endif
|
|
|
|
/*
|
|
* This does the RCU processing work from softirq context.
|
|
*/
|
|
static void __rcu_process_callbacks(struct rcu_ctrlblk *rcp,
|
|
struct rcu_data *rdp)
|
|
{
|
|
unsigned long flags;
|
|
long completed_snap;
|
|
|
|
if (rdp->nxtlist) {
|
|
local_irq_save(flags);
|
|
completed_snap = ACCESS_ONCE(rcp->completed);
|
|
|
|
/*
|
|
* move the other grace-period-completed entries to
|
|
* [rdp->nxtlist, *rdp->nxttail[0]) temporarily
|
|
*/
|
|
if (!rcu_batch_before(completed_snap, rdp->batch))
|
|
rdp->nxttail[0] = rdp->nxttail[1] = rdp->nxttail[2];
|
|
else if (!rcu_batch_before(completed_snap, rdp->batch - 1))
|
|
rdp->nxttail[0] = rdp->nxttail[1];
|
|
|
|
/*
|
|
* the grace period for entries in
|
|
* [rdp->nxtlist, *rdp->nxttail[0]) has completed and
|
|
* move these entries to donelist
|
|
*/
|
|
if (rdp->nxttail[0] != &rdp->nxtlist) {
|
|
*rdp->donetail = rdp->nxtlist;
|
|
rdp->donetail = rdp->nxttail[0];
|
|
rdp->nxtlist = *rdp->nxttail[0];
|
|
*rdp->donetail = NULL;
|
|
|
|
if (rdp->nxttail[1] == rdp->nxttail[0])
|
|
rdp->nxttail[1] = &rdp->nxtlist;
|
|
if (rdp->nxttail[2] == rdp->nxttail[0])
|
|
rdp->nxttail[2] = &rdp->nxtlist;
|
|
rdp->nxttail[0] = &rdp->nxtlist;
|
|
}
|
|
|
|
local_irq_restore(flags);
|
|
|
|
if (rcu_batch_after(rdp->batch, rcp->pending)) {
|
|
unsigned long flags2;
|
|
|
|
/* and start it/schedule start if it's a new batch */
|
|
spin_lock_irqsave(&rcp->lock, flags2);
|
|
if (rcu_batch_after(rdp->batch, rcp->pending)) {
|
|
rcp->pending = rdp->batch;
|
|
rcu_start_batch(rcp);
|
|
}
|
|
spin_unlock_irqrestore(&rcp->lock, flags2);
|
|
}
|
|
}
|
|
|
|
rcu_check_quiescent_state(rcp, rdp);
|
|
if (rdp->donelist)
|
|
rcu_do_batch(rdp);
|
|
}
|
|
|
|
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 see before any RCU
|
|
* grace-period manupulations below.
|
|
*/
|
|
|
|
smp_mb(); /* See above block comment. */
|
|
|
|
__rcu_process_callbacks(&rcu_ctrlblk, &__get_cpu_var(rcu_data));
|
|
__rcu_process_callbacks(&rcu_bh_ctrlblk, &__get_cpu_var(rcu_bh_data));
|
|
|
|
/*
|
|
* Memory references from any later RCU read-side critical sections
|
|
* executed by the interrupted code must be see after any RCU
|
|
* grace-period manupulations above.
|
|
*/
|
|
|
|
smp_mb(); /* See above block comment. */
|
|
}
|
|
|
|
static int __rcu_pending(struct rcu_ctrlblk *rcp, struct rcu_data *rdp)
|
|
{
|
|
/* Check for CPU stalls, if enabled. */
|
|
check_cpu_stall(rcp);
|
|
|
|
if (rdp->nxtlist) {
|
|
long completed_snap = ACCESS_ONCE(rcp->completed);
|
|
|
|
/*
|
|
* This cpu has pending rcu entries and the grace period
|
|
* for them has completed.
|
|
*/
|
|
if (!rcu_batch_before(completed_snap, rdp->batch))
|
|
return 1;
|
|
if (!rcu_batch_before(completed_snap, rdp->batch - 1) &&
|
|
rdp->nxttail[0] != rdp->nxttail[1])
|
|
return 1;
|
|
if (rdp->nxttail[0] != &rdp->nxtlist)
|
|
return 1;
|
|
|
|
/*
|
|
* This cpu has pending rcu entries and the new batch
|
|
* for then hasn't been started nor scheduled start
|
|
*/
|
|
if (rcu_batch_after(rdp->batch, rcp->pending))
|
|
return 1;
|
|
}
|
|
|
|
/* This cpu has finished callbacks to invoke */
|
|
if (rdp->donelist)
|
|
return 1;
|
|
|
|
/* The rcu core waits for a quiescent state from the cpu */
|
|
if (rdp->quiescbatch != rcp->cur || rdp->qs_pending)
|
|
return 1;
|
|
|
|
/* nothing to do */
|
|
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.
|
|
*/
|
|
int rcu_pending(int cpu)
|
|
{
|
|
return __rcu_pending(&rcu_ctrlblk, &per_cpu(rcu_data, cpu)) ||
|
|
__rcu_pending(&rcu_bh_ctrlblk, &per_cpu(rcu_bh_data, 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. This function is part of the RCU implementation; it is -not-
|
|
* an exported member of the RCU API.
|
|
*/
|
|
int rcu_needs_cpu(int cpu)
|
|
{
|
|
struct rcu_data *rdp = &per_cpu(rcu_data, cpu);
|
|
struct rcu_data *rdp_bh = &per_cpu(rcu_bh_data, cpu);
|
|
|
|
return !!rdp->nxtlist || !!rdp_bh->nxtlist || rcu_pending(cpu);
|
|
}
|
|
|
|
/*
|
|
* Top-level function driving RCU grace-period detection, normally
|
|
* invoked from the scheduler-clock interrupt. This function simply
|
|
* increments counters that are read only from softirq by this same
|
|
* CPU, so there are no memory barriers required.
|
|
*/
|
|
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 count it.
|
|
*
|
|
* Also do a memory barrier. This is needed to handle
|
|
* the case where writes from a preempt-disable section
|
|
* of code get reordered into schedule() by this CPU's
|
|
* write buffer. The memory barrier makes sure that
|
|
* the rcu_qsctr_inc() and rcu_bh_qsctr_inc() are see
|
|
* by other CPUs to happen after any such write.
|
|
*/
|
|
|
|
smp_mb(); /* See above block comment. */
|
|
rcu_qsctr_inc(cpu);
|
|
rcu_bh_qsctr_inc(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 count it. The memory barrier
|
|
* is needed for the same reason as is the above one.
|
|
*/
|
|
|
|
smp_mb(); /* See above block comment. */
|
|
rcu_bh_qsctr_inc(cpu);
|
|
}
|
|
raise_rcu_softirq();
|
|
}
|
|
|
|
static void __cpuinit rcu_init_percpu_data(int cpu, struct rcu_ctrlblk *rcp,
|
|
struct rcu_data *rdp)
|
|
{
|
|
unsigned long flags;
|
|
|
|
spin_lock_irqsave(&rcp->lock, flags);
|
|
memset(rdp, 0, sizeof(*rdp));
|
|
rdp->nxttail[0] = rdp->nxttail[1] = rdp->nxttail[2] = &rdp->nxtlist;
|
|
rdp->donetail = &rdp->donelist;
|
|
rdp->quiescbatch = rcp->completed;
|
|
rdp->qs_pending = 0;
|
|
rdp->cpu = cpu;
|
|
rdp->blimit = blimit;
|
|
spin_unlock_irqrestore(&rcp->lock, flags);
|
|
}
|
|
|
|
static void __cpuinit rcu_online_cpu(int cpu)
|
|
{
|
|
struct rcu_data *rdp = &per_cpu(rcu_data, cpu);
|
|
struct rcu_data *bh_rdp = &per_cpu(rcu_bh_data, cpu);
|
|
|
|
rcu_init_percpu_data(cpu, &rcu_ctrlblk, rdp);
|
|
rcu_init_percpu_data(cpu, &rcu_bh_ctrlblk, bh_rdp);
|
|
open_softirq(RCU_SOFTIRQ, rcu_process_callbacks);
|
|
}
|
|
|
|
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_DEAD:
|
|
case CPU_DEAD_FROZEN:
|
|
rcu_offline_cpu(cpu);
|
|
break;
|
|
default:
|
|
break;
|
|
}
|
|
return NOTIFY_OK;
|
|
}
|
|
|
|
static struct notifier_block __cpuinitdata rcu_nb = {
|
|
.notifier_call = rcu_cpu_notify,
|
|
};
|
|
|
|
/*
|
|
* Initializes rcu mechanism. Assumed to be called early.
|
|
* That is before local timer(SMP) or jiffie timer (uniproc) is setup.
|
|
* Note that rcu_qsctr and friends are implicitly
|
|
* initialized due to the choice of ``0'' for RCU_CTR_INVALID.
|
|
*/
|
|
void __init __rcu_init(void)
|
|
{
|
|
#ifdef CONFIG_RCU_CPU_STALL_DETECTOR
|
|
printk(KERN_INFO "RCU-based detection of stalled CPUs is enabled.\n");
|
|
#endif /* #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */
|
|
rcu_cpu_notify(&rcu_nb, CPU_UP_PREPARE,
|
|
(void *)(long)smp_processor_id());
|
|
/* Register notifier for non-boot CPUs */
|
|
register_cpu_notifier(&rcu_nb);
|
|
}
|
|
|
|
module_param(blimit, int, 0);
|
|
module_param(qhimark, int, 0);
|
|
module_param(qlowmark, int, 0);
|