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4446a36ff8
Fourth cut of patch to provide the call_rcu_sched(). This is again to synchronize_sched() as call_rcu() is to synchronize_rcu(). Should be fine for experimental and -rt use, but not ready for inclusion. With some luck, I will be able to tell Andrew to come out of hiding on the next round. Passes multi-day rcutorture sessions with concurrent CPU hotplugging. Fixes since the first version include a bug that could result in indefinite blocking (spotted by Gautham Shenoy), better resiliency against CPU-hotplug operations, and other minor fixes. Fixes since the second version include reworking grace-period detection to avoid deadlocks that could happen when running concurrently with CPU hotplug, adding Mathieu's fix to avoid the softlockup messages, as well as Mathieu's fix to allow use earlier in boot. Fixes since the third version include a wrong-CPU bug spotted by Andrew, getting rid of the obsolete synchronize_kernel API that somehow snuck back in, merging spin_unlock() and local_irq_restore() in a few places, commenting the code that checks for quiescent states based on interrupting from user-mode execution or the idle loop, removing some inline attributes, and some code-style changes. Known/suspected shortcomings: o I still do not entirely trust the sleep/wakeup logic. Next step will be to use a private snapshot of the CPU online mask in rcu_sched_grace_period() -- if the CPU wasn't there at the start of the grace period, we don't need to hear from it. And the bit about accounting for changes in online CPUs inside of rcu_sched_grace_period() is ugly anyway. o It might be good for rcu_sched_grace_period() to invoke resched_cpu() when a given CPU wasn't responding quickly, but resched_cpu() is declared static... This patch also fixes a long-standing bug in the earlier preemptable-RCU implementation of synchronize_rcu() that could result in loss of concurrent external changes to a task's CPU affinity mask. I still cannot remember who reported this... Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
136 lines
4.3 KiB
C
136 lines
4.3 KiB
C
/*
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* Read-Copy Update mechanism for mutual exclusion (RT implementation)
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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 (C) IBM Corporation, 2006
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*
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* Author: Paul McKenney <paulmck@us.ibm.com>
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*
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* Based on the original work by Paul McKenney <paul.mckenney@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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#ifndef __LINUX_RCUPREEMPT_H
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#define __LINUX_RCUPREEMPT_H
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#include <linux/cache.h>
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#include <linux/spinlock.h>
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#include <linux/threads.h>
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#include <linux/percpu.h>
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#include <linux/cpumask.h>
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#include <linux/seqlock.h>
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struct rcu_dyntick_sched {
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int dynticks;
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int dynticks_snap;
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int sched_qs;
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int sched_qs_snap;
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int sched_dynticks_snap;
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};
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DECLARE_PER_CPU(struct rcu_dyntick_sched, rcu_dyntick_sched);
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static inline void rcu_qsctr_inc(int cpu)
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{
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struct rcu_dyntick_sched *rdssp = &per_cpu(rcu_dyntick_sched, cpu);
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rdssp->sched_qs++;
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}
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#define rcu_bh_qsctr_inc(cpu)
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#define call_rcu_bh(head, rcu) call_rcu(head, rcu)
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/**
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* call_rcu_sched - Queue RCU callback for invocation after sched 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
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* synchronize_sched()-style grace period elapses, in other words after
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* all currently executing preempt-disabled sections of code (including
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* hardirq handlers, NMI handlers, and local_irq_save() blocks) have
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* completed.
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*/
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extern void call_rcu_sched(struct rcu_head *head,
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void (*func)(struct rcu_head *head));
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extern void __rcu_read_lock(void) __acquires(RCU);
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extern void __rcu_read_unlock(void) __releases(RCU);
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extern int rcu_pending(int cpu);
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extern int rcu_needs_cpu(int cpu);
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#define __rcu_read_lock_bh() { rcu_read_lock(); local_bh_disable(); }
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#define __rcu_read_unlock_bh() { local_bh_enable(); rcu_read_unlock(); }
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extern void __synchronize_sched(void);
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extern void __rcu_init(void);
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extern void rcu_init_sched(void);
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extern void rcu_check_callbacks(int cpu, int user);
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extern void rcu_restart_cpu(int cpu);
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extern long rcu_batches_completed(void);
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/*
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* Return the number of RCU batches processed thus far. Useful for debug
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* and statistic. The _bh variant is identifcal to straight RCU
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*/
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static inline long rcu_batches_completed_bh(void)
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{
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return rcu_batches_completed();
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}
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#ifdef CONFIG_RCU_TRACE
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struct rcupreempt_trace;
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extern long *rcupreempt_flipctr(int cpu);
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extern long rcupreempt_data_completed(void);
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extern int rcupreempt_flip_flag(int cpu);
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extern int rcupreempt_mb_flag(int cpu);
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extern char *rcupreempt_try_flip_state_name(void);
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extern struct rcupreempt_trace *rcupreempt_trace_cpu(int cpu);
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#endif
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struct softirq_action;
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#ifdef CONFIG_NO_HZ
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DECLARE_PER_CPU(struct rcu_dyntick_sched, rcu_dyntick_sched);
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static inline void rcu_enter_nohz(void)
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{
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smp_mb(); /* CPUs seeing ++ must see prior RCU read-side crit sects */
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__get_cpu_var(rcu_dyntick_sched).dynticks++;
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WARN_ON(__get_cpu_var(rcu_dyntick_sched).dynticks & 0x1);
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}
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static inline void rcu_exit_nohz(void)
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{
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smp_mb(); /* CPUs seeing ++ must see later RCU read-side crit sects */
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__get_cpu_var(rcu_dyntick_sched).dynticks++;
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WARN_ON(!(__get_cpu_var(rcu_dyntick_sched).dynticks & 0x1));
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}
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#else /* CONFIG_NO_HZ */
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#define rcu_enter_nohz() do { } while (0)
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#define rcu_exit_nohz() do { } while (0)
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#endif /* CONFIG_NO_HZ */
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#endif /* __LINUX_RCUPREEMPT_H */
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