e0ecfa7917
Fix rcu_barrier() to work properly in preemptive kernel environment. Also, the ordering of callback must be preserved while moving callbacks to another CPU during CPU hotplug. Signed-off-by: Gautham R Shenoy <ego@in.ibm.com> Signed-off-by: Dipankar Sarma <dipankar@in.ibm.com> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Reviewed-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
139 lines
4.1 KiB
C
139 lines
4.1 KiB
C
/*
|
|
* Read-Copy Update mechanism for mutual exclusion
|
|
*
|
|
* This program is free software; you can redistribute it and/or modify
|
|
* it under the terms of the GNU General Public License as published by
|
|
* the Free Software Foundation; either version 2 of the License, or
|
|
* (at your option) any later version.
|
|
*
|
|
* This program is distributed in the hope that it will be useful,
|
|
* but WITHOUT ANY WARRANTY; without even the implied warranty of
|
|
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
|
|
* GNU General Public License for more details.
|
|
*
|
|
* You should have received a copy of the GNU General Public License
|
|
* along with this program; if not, write to the Free Software
|
|
* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
|
|
*
|
|
* Copyright IBM Corporation, 2001
|
|
*
|
|
* Authors: Dipankar Sarma <dipankar@in.ibm.com>
|
|
* Manfred Spraul <manfred@colorfullife.com>
|
|
*
|
|
* Based on the original work by Paul McKenney <paulmck@us.ibm.com>
|
|
* and inputs from Rusty Russell, Andrea Arcangeli and Andi Kleen.
|
|
* Papers:
|
|
* http://www.rdrop.com/users/paulmck/paper/rclockpdcsproof.pdf
|
|
* http://lse.sourceforge.net/locking/rclock_OLS.2001.05.01c.sc.pdf (OLS2001)
|
|
*
|
|
* For detailed explanation of Read-Copy Update mechanism see -
|
|
* http://lse.sourceforge.net/locking/rcupdate.html
|
|
*
|
|
*/
|
|
#include <linux/types.h>
|
|
#include <linux/kernel.h>
|
|
#include <linux/init.h>
|
|
#include <linux/spinlock.h>
|
|
#include <linux/smp.h>
|
|
#include <linux/interrupt.h>
|
|
#include <linux/sched.h>
|
|
#include <asm/atomic.h>
|
|
#include <linux/bitops.h>
|
|
#include <linux/completion.h>
|
|
#include <linux/percpu.h>
|
|
#include <linux/notifier.h>
|
|
#include <linux/cpu.h>
|
|
#include <linux/mutex.h>
|
|
#include <linux/module.h>
|
|
|
|
struct rcu_synchronize {
|
|
struct rcu_head head;
|
|
struct completion completion;
|
|
};
|
|
|
|
static DEFINE_PER_CPU(struct rcu_head, rcu_barrier_head) = {NULL};
|
|
static atomic_t rcu_barrier_cpu_count;
|
|
static DEFINE_MUTEX(rcu_barrier_mutex);
|
|
static struct completion rcu_barrier_completion;
|
|
|
|
/* Because of FASTCALL declaration of complete, we use this wrapper */
|
|
static void wakeme_after_rcu(struct rcu_head *head)
|
|
{
|
|
struct rcu_synchronize *rcu;
|
|
|
|
rcu = container_of(head, struct rcu_synchronize, head);
|
|
complete(&rcu->completion);
|
|
}
|
|
|
|
/**
|
|
* synchronize_rcu - wait until a grace period has elapsed.
|
|
*
|
|
* Control will return to the caller some time after a full grace
|
|
* period has elapsed, in other words after all currently executing RCU
|
|
* read-side critical sections have completed. RCU read-side critical
|
|
* sections are delimited by rcu_read_lock() and rcu_read_unlock(),
|
|
* and may be nested.
|
|
*/
|
|
void synchronize_rcu(void)
|
|
{
|
|
struct rcu_synchronize rcu;
|
|
|
|
init_completion(&rcu.completion);
|
|
/* Will wake me after RCU finished */
|
|
call_rcu(&rcu.head, wakeme_after_rcu);
|
|
|
|
/* Wait for it */
|
|
wait_for_completion(&rcu.completion);
|
|
}
|
|
EXPORT_SYMBOL_GPL(synchronize_rcu);
|
|
|
|
static void rcu_barrier_callback(struct rcu_head *notused)
|
|
{
|
|
if (atomic_dec_and_test(&rcu_barrier_cpu_count))
|
|
complete(&rcu_barrier_completion);
|
|
}
|
|
|
|
/*
|
|
* Called with preemption disabled, and from cross-cpu IRQ context.
|
|
*/
|
|
static void rcu_barrier_func(void *notused)
|
|
{
|
|
int cpu = smp_processor_id();
|
|
struct rcu_head *head = &per_cpu(rcu_barrier_head, cpu);
|
|
|
|
atomic_inc(&rcu_barrier_cpu_count);
|
|
call_rcu(head, rcu_barrier_callback);
|
|
}
|
|
|
|
/**
|
|
* rcu_barrier - Wait until all the in-flight RCUs are complete.
|
|
*/
|
|
void rcu_barrier(void)
|
|
{
|
|
BUG_ON(in_interrupt());
|
|
/* Take cpucontrol mutex to protect against CPU hotplug */
|
|
mutex_lock(&rcu_barrier_mutex);
|
|
init_completion(&rcu_barrier_completion);
|
|
atomic_set(&rcu_barrier_cpu_count, 0);
|
|
/*
|
|
* The queueing of callbacks in all CPUs must be atomic with
|
|
* respect to RCU, otherwise one CPU may queue a callback,
|
|
* wait for a grace period, decrement barrier count and call
|
|
* complete(), while other CPUs have not yet queued anything.
|
|
* So, we need to make sure that grace periods cannot complete
|
|
* until all the callbacks are queued.
|
|
*/
|
|
rcu_read_lock();
|
|
on_each_cpu(rcu_barrier_func, NULL, 0, 1);
|
|
rcu_read_unlock();
|
|
wait_for_completion(&rcu_barrier_completion);
|
|
mutex_unlock(&rcu_barrier_mutex);
|
|
}
|
|
EXPORT_SYMBOL_GPL(rcu_barrier);
|
|
|
|
void __init rcu_init(void)
|
|
{
|
|
__rcu_init();
|
|
}
|
|
|