mirror of
https://github.com/AuxXxilium/linux_dsm_epyc7002.git
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7d0ae8086b
This commit moves from the old ACCESS_ONCE() API to the new READ_ONCE() and WRITE_ONCE() APIs. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> [ paulmck: Updated to include kernel/torture.c as suggested by Jason Low. ]
832 lines
25 KiB
C
832 lines
25 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, you can access it online at
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* http://www.gnu.org/licenses/gpl-2.0.html.
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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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* http://lse.sourceforge.net/locking/rcupdate.html
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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/interrupt.h>
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#include <linux/sched.h>
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#include <linux/atomic.h>
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#include <linux/bitops.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/export.h>
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#include <linux/hardirq.h>
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#include <linux/delay.h>
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#include <linux/module.h>
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#include <linux/kthread.h>
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#include <linux/tick.h>
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#define CREATE_TRACE_POINTS
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#include "rcu.h"
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MODULE_ALIAS("rcupdate");
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#ifdef MODULE_PARAM_PREFIX
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#undef MODULE_PARAM_PREFIX
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#endif
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#define MODULE_PARAM_PREFIX "rcupdate."
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module_param(rcu_expedited, int, 0);
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#ifndef CONFIG_TINY_RCU
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static atomic_t rcu_expedited_nesting =
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ATOMIC_INIT(IS_ENABLED(CONFIG_RCU_EXPEDITE_BOOT) ? 1 : 0);
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/*
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* Should normal grace-period primitives be expedited? Intended for
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* use within RCU. Note that this function takes the rcu_expedited
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* sysfs/boot variable into account as well as the rcu_expedite_gp()
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* nesting. So looping on rcu_unexpedite_gp() until rcu_gp_is_expedited()
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* returns false is a -really- bad idea.
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*/
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bool rcu_gp_is_expedited(void)
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{
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return rcu_expedited || atomic_read(&rcu_expedited_nesting);
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}
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EXPORT_SYMBOL_GPL(rcu_gp_is_expedited);
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/**
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* rcu_expedite_gp - Expedite future RCU grace periods
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*
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* After a call to this function, future calls to synchronize_rcu() and
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* friends act as the corresponding synchronize_rcu_expedited() function
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* had instead been called.
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*/
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void rcu_expedite_gp(void)
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{
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atomic_inc(&rcu_expedited_nesting);
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}
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EXPORT_SYMBOL_GPL(rcu_expedite_gp);
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/**
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* rcu_unexpedite_gp - Cancel prior rcu_expedite_gp() invocation
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*
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* Undo a prior call to rcu_expedite_gp(). If all prior calls to
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* rcu_expedite_gp() are undone by a subsequent call to rcu_unexpedite_gp(),
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* and if the rcu_expedited sysfs/boot parameter is not set, then all
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* subsequent calls to synchronize_rcu() and friends will return to
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* their normal non-expedited behavior.
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*/
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void rcu_unexpedite_gp(void)
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{
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atomic_dec(&rcu_expedited_nesting);
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}
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EXPORT_SYMBOL_GPL(rcu_unexpedite_gp);
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#endif /* #ifndef CONFIG_TINY_RCU */
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/*
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* Inform RCU of the end of the in-kernel boot sequence.
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*/
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void rcu_end_inkernel_boot(void)
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{
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if (IS_ENABLED(CONFIG_RCU_EXPEDITE_BOOT))
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rcu_unexpedite_gp();
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}
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#ifdef CONFIG_PREEMPT_RCU
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/*
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* Preemptible RCU implementation for rcu_read_lock().
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* Just increment ->rcu_read_lock_nesting, shared state will be updated
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* if we block.
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*/
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void __rcu_read_lock(void)
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{
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current->rcu_read_lock_nesting++;
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barrier(); /* critical section after entry code. */
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}
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EXPORT_SYMBOL_GPL(__rcu_read_lock);
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/*
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* Preemptible RCU implementation for rcu_read_unlock().
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* Decrement ->rcu_read_lock_nesting. If the result is zero (outermost
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* rcu_read_unlock()) and ->rcu_read_unlock_special is non-zero, then
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* invoke rcu_read_unlock_special() to clean up after a context switch
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* in an RCU read-side critical section and other special cases.
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*/
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void __rcu_read_unlock(void)
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{
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struct task_struct *t = current;
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if (t->rcu_read_lock_nesting != 1) {
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--t->rcu_read_lock_nesting;
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} else {
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barrier(); /* critical section before exit code. */
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t->rcu_read_lock_nesting = INT_MIN;
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barrier(); /* assign before ->rcu_read_unlock_special load */
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if (unlikely(READ_ONCE(t->rcu_read_unlock_special.s)))
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rcu_read_unlock_special(t);
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barrier(); /* ->rcu_read_unlock_special load before assign */
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t->rcu_read_lock_nesting = 0;
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}
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#ifdef CONFIG_PROVE_LOCKING
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{
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int rrln = READ_ONCE(t->rcu_read_lock_nesting);
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WARN_ON_ONCE(rrln < 0 && rrln > INT_MIN / 2);
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}
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#endif /* #ifdef CONFIG_PROVE_LOCKING */
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}
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EXPORT_SYMBOL_GPL(__rcu_read_unlock);
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#endif /* #ifdef CONFIG_PREEMPT_RCU */
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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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static struct lock_class_key rcu_bh_lock_key;
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struct lockdep_map rcu_bh_lock_map =
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STATIC_LOCKDEP_MAP_INIT("rcu_read_lock_bh", &rcu_bh_lock_key);
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EXPORT_SYMBOL_GPL(rcu_bh_lock_map);
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static struct lock_class_key rcu_sched_lock_key;
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struct lockdep_map rcu_sched_lock_map =
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STATIC_LOCKDEP_MAP_INIT("rcu_read_lock_sched", &rcu_sched_lock_key);
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EXPORT_SYMBOL_GPL(rcu_sched_lock_map);
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static struct lock_class_key rcu_callback_key;
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struct lockdep_map rcu_callback_map =
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STATIC_LOCKDEP_MAP_INIT("rcu_callback", &rcu_callback_key);
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EXPORT_SYMBOL_GPL(rcu_callback_map);
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int notrace debug_lockdep_rcu_enabled(void)
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{
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return rcu_scheduler_active && debug_locks &&
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current->lockdep_recursion == 0;
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}
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EXPORT_SYMBOL_GPL(debug_lockdep_rcu_enabled);
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/**
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* rcu_read_lock_held() - might we be in RCU read-side critical section?
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*
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* If CONFIG_DEBUG_LOCK_ALLOC is selected, returns nonzero iff in an RCU
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* read-side critical section. In absence of CONFIG_DEBUG_LOCK_ALLOC,
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* this assumes we are in an RCU read-side critical section unless it can
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* prove otherwise. This is useful for debug checks in functions that
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* require that they be called within an RCU read-side critical section.
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*
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* Checks debug_lockdep_rcu_enabled() to prevent false positives during boot
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* and while lockdep is disabled.
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*
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* Note that rcu_read_lock() and the matching rcu_read_unlock() must
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* occur in the same context, for example, it is illegal to invoke
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* rcu_read_unlock() in process context if the matching rcu_read_lock()
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* was invoked from within an irq handler.
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*
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* Note that rcu_read_lock() is disallowed if the CPU is either idle or
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* offline from an RCU perspective, so check for those as well.
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*/
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int rcu_read_lock_held(void)
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{
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if (!debug_lockdep_rcu_enabled())
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return 1;
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if (!rcu_is_watching())
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return 0;
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if (!rcu_lockdep_current_cpu_online())
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return 0;
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return lock_is_held(&rcu_lock_map);
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}
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EXPORT_SYMBOL_GPL(rcu_read_lock_held);
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/**
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* rcu_read_lock_bh_held() - might we be in RCU-bh read-side critical section?
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*
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* Check for bottom half being disabled, which covers both the
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* CONFIG_PROVE_RCU and not cases. Note that if someone uses
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* rcu_read_lock_bh(), but then later enables BH, lockdep (if enabled)
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* will show the situation. This is useful for debug checks in functions
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* that require that they be called within an RCU read-side critical
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* section.
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*
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* Check debug_lockdep_rcu_enabled() to prevent false positives during boot.
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*
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* Note that rcu_read_lock() is disallowed if the CPU is either idle or
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* offline from an RCU perspective, so check for those as well.
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*/
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int rcu_read_lock_bh_held(void)
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{
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if (!debug_lockdep_rcu_enabled())
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return 1;
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if (!rcu_is_watching())
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return 0;
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if (!rcu_lockdep_current_cpu_online())
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return 0;
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return in_softirq() || irqs_disabled();
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}
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EXPORT_SYMBOL_GPL(rcu_read_lock_bh_held);
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#endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
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/**
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* wakeme_after_rcu() - Callback function to awaken a task after grace period
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* @head: Pointer to rcu_head member within rcu_synchronize structure
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*
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* Awaken the corresponding task now that a grace period has elapsed.
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*/
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void wakeme_after_rcu(struct rcu_head *head)
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{
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struct rcu_synchronize *rcu;
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rcu = container_of(head, struct rcu_synchronize, head);
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complete(&rcu->completion);
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}
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void wait_rcu_gp(call_rcu_func_t crf)
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{
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struct rcu_synchronize rcu;
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init_rcu_head_on_stack(&rcu.head);
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init_completion(&rcu.completion);
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/* Will wake me after RCU finished. */
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crf(&rcu.head, wakeme_after_rcu);
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/* Wait for it. */
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wait_for_completion(&rcu.completion);
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destroy_rcu_head_on_stack(&rcu.head);
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}
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EXPORT_SYMBOL_GPL(wait_rcu_gp);
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#ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD
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void init_rcu_head(struct rcu_head *head)
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{
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debug_object_init(head, &rcuhead_debug_descr);
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}
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void destroy_rcu_head(struct rcu_head *head)
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{
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debug_object_free(head, &rcuhead_debug_descr);
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}
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/*
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* fixup_activate is called when:
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* - an active object is activated
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* - an unknown object is activated (might be a statically initialized object)
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* Activation is performed internally by call_rcu().
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*/
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static int rcuhead_fixup_activate(void *addr, enum debug_obj_state state)
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{
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struct rcu_head *head = addr;
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switch (state) {
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case ODEBUG_STATE_NOTAVAILABLE:
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/*
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* This is not really a fixup. We just make sure that it is
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* tracked in the object tracker.
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*/
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debug_object_init(head, &rcuhead_debug_descr);
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debug_object_activate(head, &rcuhead_debug_descr);
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return 0;
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default:
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return 1;
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}
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}
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/**
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* init_rcu_head_on_stack() - initialize on-stack rcu_head for debugobjects
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* @head: pointer to rcu_head structure to be initialized
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*
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* This function informs debugobjects of a new rcu_head structure that
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* has been allocated as an auto variable on the stack. This function
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* is not required for rcu_head structures that are statically defined or
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* that are dynamically allocated on the heap. This function has no
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* effect for !CONFIG_DEBUG_OBJECTS_RCU_HEAD kernel builds.
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*/
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void init_rcu_head_on_stack(struct rcu_head *head)
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{
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debug_object_init_on_stack(head, &rcuhead_debug_descr);
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}
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EXPORT_SYMBOL_GPL(init_rcu_head_on_stack);
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/**
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* destroy_rcu_head_on_stack() - destroy on-stack rcu_head for debugobjects
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* @head: pointer to rcu_head structure to be initialized
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*
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* This function informs debugobjects that an on-stack rcu_head structure
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* is about to go out of scope. As with init_rcu_head_on_stack(), this
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* function is not required for rcu_head structures that are statically
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* defined or that are dynamically allocated on the heap. Also as with
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* init_rcu_head_on_stack(), this function has no effect for
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* !CONFIG_DEBUG_OBJECTS_RCU_HEAD kernel builds.
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*/
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void destroy_rcu_head_on_stack(struct rcu_head *head)
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{
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debug_object_free(head, &rcuhead_debug_descr);
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}
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EXPORT_SYMBOL_GPL(destroy_rcu_head_on_stack);
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struct debug_obj_descr rcuhead_debug_descr = {
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.name = "rcu_head",
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.fixup_activate = rcuhead_fixup_activate,
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};
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EXPORT_SYMBOL_GPL(rcuhead_debug_descr);
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#endif /* #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD */
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#if defined(CONFIG_TREE_RCU) || defined(CONFIG_PREEMPT_RCU) || defined(CONFIG_RCU_TRACE)
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void do_trace_rcu_torture_read(const char *rcutorturename, struct rcu_head *rhp,
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unsigned long secs,
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unsigned long c_old, unsigned long c)
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{
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trace_rcu_torture_read(rcutorturename, rhp, secs, c_old, c);
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}
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EXPORT_SYMBOL_GPL(do_trace_rcu_torture_read);
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#else
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#define do_trace_rcu_torture_read(rcutorturename, rhp, secs, c_old, c) \
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do { } while (0)
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#endif
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#ifdef CONFIG_RCU_STALL_COMMON
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#ifdef CONFIG_PROVE_RCU
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#define RCU_STALL_DELAY_DELTA (5 * HZ)
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#else
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#define RCU_STALL_DELAY_DELTA 0
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#endif
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int rcu_cpu_stall_suppress __read_mostly; /* 1 = suppress stall warnings. */
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static int rcu_cpu_stall_timeout __read_mostly = CONFIG_RCU_CPU_STALL_TIMEOUT;
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module_param(rcu_cpu_stall_suppress, int, 0644);
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module_param(rcu_cpu_stall_timeout, int, 0644);
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int rcu_jiffies_till_stall_check(void)
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{
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int till_stall_check = READ_ONCE(rcu_cpu_stall_timeout);
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/*
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* Limit check must be consistent with the Kconfig limits
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* for CONFIG_RCU_CPU_STALL_TIMEOUT.
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*/
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if (till_stall_check < 3) {
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WRITE_ONCE(rcu_cpu_stall_timeout, 3);
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till_stall_check = 3;
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} else if (till_stall_check > 300) {
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WRITE_ONCE(rcu_cpu_stall_timeout, 300);
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till_stall_check = 300;
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}
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return till_stall_check * HZ + RCU_STALL_DELAY_DELTA;
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}
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void rcu_sysrq_start(void)
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{
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if (!rcu_cpu_stall_suppress)
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rcu_cpu_stall_suppress = 2;
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}
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void rcu_sysrq_end(void)
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{
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if (rcu_cpu_stall_suppress == 2)
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rcu_cpu_stall_suppress = 0;
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}
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static int rcu_panic(struct notifier_block *this, unsigned long ev, void *ptr)
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{
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rcu_cpu_stall_suppress = 1;
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return NOTIFY_DONE;
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}
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static struct notifier_block rcu_panic_block = {
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.notifier_call = rcu_panic,
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};
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static int __init check_cpu_stall_init(void)
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{
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atomic_notifier_chain_register(&panic_notifier_list, &rcu_panic_block);
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return 0;
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}
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early_initcall(check_cpu_stall_init);
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#endif /* #ifdef CONFIG_RCU_STALL_COMMON */
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#ifdef CONFIG_TASKS_RCU
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/*
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* Simple variant of RCU whose quiescent states are voluntary context switch,
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* user-space execution, and idle. As such, grace periods can take one good
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* long time. There are no read-side primitives similar to rcu_read_lock()
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* and rcu_read_unlock() because this implementation is intended to get
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* the system into a safe state for some of the manipulations involved in
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* tracing and the like. Finally, this implementation does not support
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* high call_rcu_tasks() rates from multiple CPUs. If this is required,
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* per-CPU callback lists will be needed.
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*/
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/* Global list of callbacks and associated lock. */
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static struct rcu_head *rcu_tasks_cbs_head;
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static struct rcu_head **rcu_tasks_cbs_tail = &rcu_tasks_cbs_head;
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static DECLARE_WAIT_QUEUE_HEAD(rcu_tasks_cbs_wq);
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static DEFINE_RAW_SPINLOCK(rcu_tasks_cbs_lock);
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/* Track exiting tasks in order to allow them to be waited for. */
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DEFINE_SRCU(tasks_rcu_exit_srcu);
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|
|
|
/* Control stall timeouts. Disable with <= 0, otherwise jiffies till stall. */
|
|
static int rcu_task_stall_timeout __read_mostly = HZ * 60 * 10;
|
|
module_param(rcu_task_stall_timeout, int, 0644);
|
|
|
|
static void rcu_spawn_tasks_kthread(void);
|
|
|
|
/*
|
|
* Post an RCU-tasks callback. First call must be from process context
|
|
* after the scheduler if fully operational.
|
|
*/
|
|
void call_rcu_tasks(struct rcu_head *rhp, void (*func)(struct rcu_head *rhp))
|
|
{
|
|
unsigned long flags;
|
|
bool needwake;
|
|
|
|
rhp->next = NULL;
|
|
rhp->func = func;
|
|
raw_spin_lock_irqsave(&rcu_tasks_cbs_lock, flags);
|
|
needwake = !rcu_tasks_cbs_head;
|
|
*rcu_tasks_cbs_tail = rhp;
|
|
rcu_tasks_cbs_tail = &rhp->next;
|
|
raw_spin_unlock_irqrestore(&rcu_tasks_cbs_lock, flags);
|
|
if (needwake) {
|
|
rcu_spawn_tasks_kthread();
|
|
wake_up(&rcu_tasks_cbs_wq);
|
|
}
|
|
}
|
|
EXPORT_SYMBOL_GPL(call_rcu_tasks);
|
|
|
|
/**
|
|
* synchronize_rcu_tasks - wait until an rcu-tasks grace period has elapsed.
|
|
*
|
|
* Control will return to the caller some time after a full rcu-tasks
|
|
* grace period has elapsed, in other words after all currently
|
|
* executing rcu-tasks read-side critical sections have elapsed. These
|
|
* read-side critical sections are delimited by calls to schedule(),
|
|
* cond_resched_rcu_qs(), idle execution, userspace execution, calls
|
|
* to synchronize_rcu_tasks(), and (in theory, anyway) cond_resched().
|
|
*
|
|
* This is a very specialized primitive, intended only for a few uses in
|
|
* tracing and other situations requiring manipulation of function
|
|
* preambles and profiling hooks. The synchronize_rcu_tasks() function
|
|
* is not (yet) intended for heavy use from multiple CPUs.
|
|
*
|
|
* Note that this guarantee implies further memory-ordering guarantees.
|
|
* On systems with more than one CPU, when synchronize_rcu_tasks() returns,
|
|
* each CPU is guaranteed to have executed a full memory barrier since the
|
|
* end of its last RCU-tasks read-side critical section whose beginning
|
|
* preceded the call to synchronize_rcu_tasks(). In addition, each CPU
|
|
* having an RCU-tasks read-side critical section that extends beyond
|
|
* the return from synchronize_rcu_tasks() is guaranteed to have executed
|
|
* a full memory barrier after the beginning of synchronize_rcu_tasks()
|
|
* and before the beginning of that RCU-tasks read-side critical section.
|
|
* Note that these guarantees include CPUs that are offline, idle, or
|
|
* executing in user mode, as well as CPUs that are executing in the kernel.
|
|
*
|
|
* Furthermore, if CPU A invoked synchronize_rcu_tasks(), which returned
|
|
* to its caller on CPU B, then both CPU A and CPU B are guaranteed
|
|
* to have executed a full memory barrier during the execution of
|
|
* synchronize_rcu_tasks() -- even if CPU A and CPU B are the same CPU
|
|
* (but again only if the system has more than one CPU).
|
|
*/
|
|
void synchronize_rcu_tasks(void)
|
|
{
|
|
/* Complain if the scheduler has not started. */
|
|
rcu_lockdep_assert(!rcu_scheduler_active,
|
|
"synchronize_rcu_tasks called too soon");
|
|
|
|
/* Wait for the grace period. */
|
|
wait_rcu_gp(call_rcu_tasks);
|
|
}
|
|
EXPORT_SYMBOL_GPL(synchronize_rcu_tasks);
|
|
|
|
/**
|
|
* rcu_barrier_tasks - Wait for in-flight call_rcu_tasks() callbacks.
|
|
*
|
|
* Although the current implementation is guaranteed to wait, it is not
|
|
* obligated to, for example, if there are no pending callbacks.
|
|
*/
|
|
void rcu_barrier_tasks(void)
|
|
{
|
|
/* There is only one callback queue, so this is easy. ;-) */
|
|
synchronize_rcu_tasks();
|
|
}
|
|
EXPORT_SYMBOL_GPL(rcu_barrier_tasks);
|
|
|
|
/* See if tasks are still holding out, complain if so. */
|
|
static void check_holdout_task(struct task_struct *t,
|
|
bool needreport, bool *firstreport)
|
|
{
|
|
int cpu;
|
|
|
|
if (!READ_ONCE(t->rcu_tasks_holdout) ||
|
|
t->rcu_tasks_nvcsw != READ_ONCE(t->nvcsw) ||
|
|
!READ_ONCE(t->on_rq) ||
|
|
(IS_ENABLED(CONFIG_NO_HZ_FULL) &&
|
|
!is_idle_task(t) && t->rcu_tasks_idle_cpu >= 0)) {
|
|
WRITE_ONCE(t->rcu_tasks_holdout, false);
|
|
list_del_init(&t->rcu_tasks_holdout_list);
|
|
put_task_struct(t);
|
|
return;
|
|
}
|
|
if (!needreport)
|
|
return;
|
|
if (*firstreport) {
|
|
pr_err("INFO: rcu_tasks detected stalls on tasks:\n");
|
|
*firstreport = false;
|
|
}
|
|
cpu = task_cpu(t);
|
|
pr_alert("%p: %c%c nvcsw: %lu/%lu holdout: %d idle_cpu: %d/%d\n",
|
|
t, ".I"[is_idle_task(t)],
|
|
"N."[cpu < 0 || !tick_nohz_full_cpu(cpu)],
|
|
t->rcu_tasks_nvcsw, t->nvcsw, t->rcu_tasks_holdout,
|
|
t->rcu_tasks_idle_cpu, cpu);
|
|
sched_show_task(t);
|
|
}
|
|
|
|
/* RCU-tasks kthread that detects grace periods and invokes callbacks. */
|
|
static int __noreturn rcu_tasks_kthread(void *arg)
|
|
{
|
|
unsigned long flags;
|
|
struct task_struct *g, *t;
|
|
unsigned long lastreport;
|
|
struct rcu_head *list;
|
|
struct rcu_head *next;
|
|
LIST_HEAD(rcu_tasks_holdouts);
|
|
|
|
/* Run on housekeeping CPUs by default. Sysadm can move if desired. */
|
|
housekeeping_affine(current);
|
|
|
|
/*
|
|
* Each pass through the following loop makes one check for
|
|
* newly arrived callbacks, and, if there are some, waits for
|
|
* one RCU-tasks grace period and then invokes the callbacks.
|
|
* This loop is terminated by the system going down. ;-)
|
|
*/
|
|
for (;;) {
|
|
|
|
/* Pick up any new callbacks. */
|
|
raw_spin_lock_irqsave(&rcu_tasks_cbs_lock, flags);
|
|
list = rcu_tasks_cbs_head;
|
|
rcu_tasks_cbs_head = NULL;
|
|
rcu_tasks_cbs_tail = &rcu_tasks_cbs_head;
|
|
raw_spin_unlock_irqrestore(&rcu_tasks_cbs_lock, flags);
|
|
|
|
/* If there were none, wait a bit and start over. */
|
|
if (!list) {
|
|
wait_event_interruptible(rcu_tasks_cbs_wq,
|
|
rcu_tasks_cbs_head);
|
|
if (!rcu_tasks_cbs_head) {
|
|
WARN_ON(signal_pending(current));
|
|
schedule_timeout_interruptible(HZ/10);
|
|
}
|
|
continue;
|
|
}
|
|
|
|
/*
|
|
* Wait for all pre-existing t->on_rq and t->nvcsw
|
|
* transitions to complete. Invoking synchronize_sched()
|
|
* suffices because all these transitions occur with
|
|
* interrupts disabled. Without this synchronize_sched(),
|
|
* a read-side critical section that started before the
|
|
* grace period might be incorrectly seen as having started
|
|
* after the grace period.
|
|
*
|
|
* This synchronize_sched() also dispenses with the
|
|
* need for a memory barrier on the first store to
|
|
* ->rcu_tasks_holdout, as it forces the store to happen
|
|
* after the beginning of the grace period.
|
|
*/
|
|
synchronize_sched();
|
|
|
|
/*
|
|
* There were callbacks, so we need to wait for an
|
|
* RCU-tasks grace period. Start off by scanning
|
|
* the task list for tasks that are not already
|
|
* voluntarily blocked. Mark these tasks and make
|
|
* a list of them in rcu_tasks_holdouts.
|
|
*/
|
|
rcu_read_lock();
|
|
for_each_process_thread(g, t) {
|
|
if (t != current && READ_ONCE(t->on_rq) &&
|
|
!is_idle_task(t)) {
|
|
get_task_struct(t);
|
|
t->rcu_tasks_nvcsw = READ_ONCE(t->nvcsw);
|
|
WRITE_ONCE(t->rcu_tasks_holdout, true);
|
|
list_add(&t->rcu_tasks_holdout_list,
|
|
&rcu_tasks_holdouts);
|
|
}
|
|
}
|
|
rcu_read_unlock();
|
|
|
|
/*
|
|
* Wait for tasks that are in the process of exiting.
|
|
* This does only part of the job, ensuring that all
|
|
* tasks that were previously exiting reach the point
|
|
* where they have disabled preemption, allowing the
|
|
* later synchronize_sched() to finish the job.
|
|
*/
|
|
synchronize_srcu(&tasks_rcu_exit_srcu);
|
|
|
|
/*
|
|
* Each pass through the following loop scans the list
|
|
* of holdout tasks, removing any that are no longer
|
|
* holdouts. When the list is empty, we are done.
|
|
*/
|
|
lastreport = jiffies;
|
|
while (!list_empty(&rcu_tasks_holdouts)) {
|
|
bool firstreport;
|
|
bool needreport;
|
|
int rtst;
|
|
struct task_struct *t1;
|
|
|
|
schedule_timeout_interruptible(HZ);
|
|
rtst = READ_ONCE(rcu_task_stall_timeout);
|
|
needreport = rtst > 0 &&
|
|
time_after(jiffies, lastreport + rtst);
|
|
if (needreport)
|
|
lastreport = jiffies;
|
|
firstreport = true;
|
|
WARN_ON(signal_pending(current));
|
|
list_for_each_entry_safe(t, t1, &rcu_tasks_holdouts,
|
|
rcu_tasks_holdout_list) {
|
|
check_holdout_task(t, needreport, &firstreport);
|
|
cond_resched();
|
|
}
|
|
}
|
|
|
|
/*
|
|
* Because ->on_rq and ->nvcsw are not guaranteed
|
|
* to have a full memory barriers prior to them in the
|
|
* schedule() path, memory reordering on other CPUs could
|
|
* cause their RCU-tasks read-side critical sections to
|
|
* extend past the end of the grace period. However,
|
|
* because these ->nvcsw updates are carried out with
|
|
* interrupts disabled, we can use synchronize_sched()
|
|
* to force the needed ordering on all such CPUs.
|
|
*
|
|
* This synchronize_sched() also confines all
|
|
* ->rcu_tasks_holdout accesses to be within the grace
|
|
* period, avoiding the need for memory barriers for
|
|
* ->rcu_tasks_holdout accesses.
|
|
*
|
|
* In addition, this synchronize_sched() waits for exiting
|
|
* tasks to complete their final preempt_disable() region
|
|
* of execution, cleaning up after the synchronize_srcu()
|
|
* above.
|
|
*/
|
|
synchronize_sched();
|
|
|
|
/* Invoke the callbacks. */
|
|
while (list) {
|
|
next = list->next;
|
|
local_bh_disable();
|
|
list->func(list);
|
|
local_bh_enable();
|
|
list = next;
|
|
cond_resched();
|
|
}
|
|
schedule_timeout_uninterruptible(HZ/10);
|
|
}
|
|
}
|
|
|
|
/* Spawn rcu_tasks_kthread() at first call to call_rcu_tasks(). */
|
|
static void rcu_spawn_tasks_kthread(void)
|
|
{
|
|
static DEFINE_MUTEX(rcu_tasks_kthread_mutex);
|
|
static struct task_struct *rcu_tasks_kthread_ptr;
|
|
struct task_struct *t;
|
|
|
|
if (READ_ONCE(rcu_tasks_kthread_ptr)) {
|
|
smp_mb(); /* Ensure caller sees full kthread. */
|
|
return;
|
|
}
|
|
mutex_lock(&rcu_tasks_kthread_mutex);
|
|
if (rcu_tasks_kthread_ptr) {
|
|
mutex_unlock(&rcu_tasks_kthread_mutex);
|
|
return;
|
|
}
|
|
t = kthread_run(rcu_tasks_kthread, NULL, "rcu_tasks_kthread");
|
|
BUG_ON(IS_ERR(t));
|
|
smp_mb(); /* Ensure others see full kthread. */
|
|
WRITE_ONCE(rcu_tasks_kthread_ptr, t);
|
|
mutex_unlock(&rcu_tasks_kthread_mutex);
|
|
}
|
|
|
|
#endif /* #ifdef CONFIG_TASKS_RCU */
|
|
|
|
#ifdef CONFIG_PROVE_RCU
|
|
|
|
/*
|
|
* Early boot self test parameters, one for each flavor
|
|
*/
|
|
static bool rcu_self_test;
|
|
static bool rcu_self_test_bh;
|
|
static bool rcu_self_test_sched;
|
|
|
|
module_param(rcu_self_test, bool, 0444);
|
|
module_param(rcu_self_test_bh, bool, 0444);
|
|
module_param(rcu_self_test_sched, bool, 0444);
|
|
|
|
static int rcu_self_test_counter;
|
|
|
|
static void test_callback(struct rcu_head *r)
|
|
{
|
|
rcu_self_test_counter++;
|
|
pr_info("RCU test callback executed %d\n", rcu_self_test_counter);
|
|
}
|
|
|
|
static void early_boot_test_call_rcu(void)
|
|
{
|
|
static struct rcu_head head;
|
|
|
|
call_rcu(&head, test_callback);
|
|
}
|
|
|
|
static void early_boot_test_call_rcu_bh(void)
|
|
{
|
|
static struct rcu_head head;
|
|
|
|
call_rcu_bh(&head, test_callback);
|
|
}
|
|
|
|
static void early_boot_test_call_rcu_sched(void)
|
|
{
|
|
static struct rcu_head head;
|
|
|
|
call_rcu_sched(&head, test_callback);
|
|
}
|
|
|
|
void rcu_early_boot_tests(void)
|
|
{
|
|
pr_info("Running RCU self tests\n");
|
|
|
|
if (rcu_self_test)
|
|
early_boot_test_call_rcu();
|
|
if (rcu_self_test_bh)
|
|
early_boot_test_call_rcu_bh();
|
|
if (rcu_self_test_sched)
|
|
early_boot_test_call_rcu_sched();
|
|
}
|
|
|
|
static int rcu_verify_early_boot_tests(void)
|
|
{
|
|
int ret = 0;
|
|
int early_boot_test_counter = 0;
|
|
|
|
if (rcu_self_test) {
|
|
early_boot_test_counter++;
|
|
rcu_barrier();
|
|
}
|
|
if (rcu_self_test_bh) {
|
|
early_boot_test_counter++;
|
|
rcu_barrier_bh();
|
|
}
|
|
if (rcu_self_test_sched) {
|
|
early_boot_test_counter++;
|
|
rcu_barrier_sched();
|
|
}
|
|
|
|
if (rcu_self_test_counter != early_boot_test_counter) {
|
|
WARN_ON(1);
|
|
ret = -1;
|
|
}
|
|
|
|
return ret;
|
|
}
|
|
late_initcall(rcu_verify_early_boot_tests);
|
|
#else
|
|
void rcu_early_boot_tests(void) {}
|
|
#endif /* CONFIG_PROVE_RCU */
|