mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
synced 2024-09-03 17:40:04 +00:00
![Paul E. McKenney](/assets/img/avatar_default.png)
Ingo Molnar reported this lockup: [ 200.380003] Hangcheck: hangcheck value past margin! [ 248.192003] INFO: task S99local:2974 blocked for more than 120 seconds. [ 248.194532] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. [ 248.202330] S99local D 0000000c 6256 2974 2687 0x00000000 [ 248.208929] 9c7ebe90 00000086 6b67ef8b 0000000c 9f25a610 81a69869 00000001 820b6990 [ 248.216123] 820b6990 820b6990 9c6e4c20 9c6e4eb4 82c78990 00000000 6b993559 0000000c [ 248.220616] 9c7ebe90 8105f22a 9c6e4eb4 9c6e4c20 00000001 9c7ebe98 9c7ebeb4 81a65cb3 [ 248.229990] Call Trace: [ 248.234049] [<81a69869>] ? _spin_unlock_irqrestore+0x22/0x37 [ 248.239769] [<8105f22a>] ? prepare_to_wait+0x48/0x4e [ 248.244796] [<81a65cb3>] rcu_barrier_cpu_hotplug+0xaa/0xc9 [ 248.250343] [<8105f029>] ? autoremove_wake_function+0x0/0x38 [ 248.256063] [<81062cf2>] notifier_call_chain+0x49/0x71 [ 248.261263] [<81062da0>] raw_notifier_call_chain+0x11/0x13 [ 248.266809] [<81a0b475>] _cpu_down+0x272/0x288 [ 248.271316] [<81a0b4d5>] cpu_down+0x4a/0xa2 [ 248.275563] [<81a0c48a>] store_online+0x2a/0x5e [ 248.280156] [<81a0c460>] ? store_online+0x0/0x5e [ 248.284836] [<814ddc35>] sysdev_store+0x20/0x28 [ 248.289429] [<8112e403>] sysfs_write_file+0xb8/0xe3 [ 248.294369] [<8112e34b>] ? sysfs_write_file+0x0/0xe3 [ 248.299396] [<810e4c8f>] vfs_write+0x91/0x120 [ 248.303817] [<810e4dc1>] sys_write+0x40/0x65 [ 248.308150] [<81002d73>] sysenter_do_call+0x12/0x28 This change moves an RCU grace period delay off of the critical path for CPU-hotunplug operations. Since RCU callback migration is only performed on CPU-hotunplug operations, and since the rcu_barrier() race is provoked only by consecutive CPU-hotunplug operations, it is not necessary to delay the end of a given CPU-hotunplug operation. We can instead choose to delay the beginning of the next CPU-hotunplug operation. Reported-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Josh Triplett <josht@linux.vnet.ibm.com> Cc: laijs@cn.fujitsu.com Cc: dipankar@in.ibm.com Cc: akpm@linux-foundation.org Cc: mathieu.desnoyers@polymtl.ca Cc: dvhltc@us.ibm.com Cc: niv@us.ibm.com Cc: peterz@infradead.org Cc: rostedt@goodmis.org Cc: hugh.dickins@tiscali.co.uk Cc: benh@kernel.crashing.org LKML-Reference: <20090819060614.GA14383@linux.vnet.ibm.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
271 lines
7.8 KiB
C
271 lines
7.8 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/percpu.h>
|
|
#include <linux/notifier.h>
|
|
#include <linux/cpu.h>
|
|
#include <linux/mutex.h>
|
|
#include <linux/module.h>
|
|
#include <linux/kernel_stat.h>
|
|
|
|
enum rcu_barrier {
|
|
RCU_BARRIER_STD,
|
|
RCU_BARRIER_BH,
|
|
RCU_BARRIER_SCHED,
|
|
};
|
|
|
|
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;
|
|
int rcu_scheduler_active __read_mostly;
|
|
|
|
static atomic_t rcu_migrate_type_count = ATOMIC_INIT(0);
|
|
static struct rcu_head rcu_migrate_head[3];
|
|
static DECLARE_WAIT_QUEUE_HEAD(rcu_migrate_wq);
|
|
|
|
/*
|
|
* Awaken the corresponding synchronize_rcu() instance now that a
|
|
* grace period has elapsed.
|
|
*/
|
|
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;
|
|
|
|
if (rcu_blocking_is_gp())
|
|
return;
|
|
|
|
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);
|
|
|
|
/**
|
|
* synchronize_rcu_bh - wait until an rcu_bh grace period has elapsed.
|
|
*
|
|
* Control will return to the caller some time after a full rcu_bh grace
|
|
* period has elapsed, in other words after all currently executing rcu_bh
|
|
* read-side critical sections have completed. RCU read-side critical
|
|
* sections are delimited by rcu_read_lock_bh() and rcu_read_unlock_bh(),
|
|
* and may be nested.
|
|
*/
|
|
void synchronize_rcu_bh(void)
|
|
{
|
|
struct rcu_synchronize rcu;
|
|
|
|
if (rcu_blocking_is_gp())
|
|
return;
|
|
|
|
init_completion(&rcu.completion);
|
|
/* Will wake me after RCU finished. */
|
|
call_rcu_bh(&rcu.head, wakeme_after_rcu);
|
|
/* Wait for it. */
|
|
wait_for_completion(&rcu.completion);
|
|
}
|
|
EXPORT_SYMBOL_GPL(synchronize_rcu_bh);
|
|
|
|
static void rcu_barrier_callback(struct rcu_head *notused)
|
|
{
|
|
if (atomic_dec_and_test(&rcu_barrier_cpu_count))
|
|
complete(&rcu_barrier_completion);
|
|
}
|
|
|
|
/*
|
|
* Called with preemption disabled, and from cross-cpu IRQ context.
|
|
*/
|
|
static void rcu_barrier_func(void *type)
|
|
{
|
|
int cpu = smp_processor_id();
|
|
struct rcu_head *head = &per_cpu(rcu_barrier_head, cpu);
|
|
|
|
atomic_inc(&rcu_barrier_cpu_count);
|
|
switch ((enum rcu_barrier)type) {
|
|
case RCU_BARRIER_STD:
|
|
call_rcu(head, rcu_barrier_callback);
|
|
break;
|
|
case RCU_BARRIER_BH:
|
|
call_rcu_bh(head, rcu_barrier_callback);
|
|
break;
|
|
case RCU_BARRIER_SCHED:
|
|
call_rcu_sched(head, rcu_barrier_callback);
|
|
break;
|
|
}
|
|
}
|
|
|
|
static inline void wait_migrated_callbacks(void)
|
|
{
|
|
wait_event(rcu_migrate_wq, !atomic_read(&rcu_migrate_type_count));
|
|
smp_mb(); /* In case we didn't sleep. */
|
|
}
|
|
|
|
/*
|
|
* Orchestrate the specified type of RCU barrier, waiting for all
|
|
* RCU callbacks of the specified type to complete.
|
|
*/
|
|
static void _rcu_barrier(enum rcu_barrier type)
|
|
{
|
|
BUG_ON(in_interrupt());
|
|
/* Take cpucontrol mutex to protect against CPU hotplug */
|
|
mutex_lock(&rcu_barrier_mutex);
|
|
init_completion(&rcu_barrier_completion);
|
|
/*
|
|
* Initialize rcu_barrier_cpu_count to 1, then invoke
|
|
* rcu_barrier_func() on each CPU, so that each CPU also has
|
|
* incremented rcu_barrier_cpu_count. Only then is it safe to
|
|
* decrement rcu_barrier_cpu_count -- otherwise the first CPU
|
|
* might complete its grace period before all of the other CPUs
|
|
* did their increment, causing this function to return too
|
|
* early.
|
|
*/
|
|
atomic_set(&rcu_barrier_cpu_count, 1);
|
|
on_each_cpu(rcu_barrier_func, (void *)type, 1);
|
|
if (atomic_dec_and_test(&rcu_barrier_cpu_count))
|
|
complete(&rcu_barrier_completion);
|
|
wait_for_completion(&rcu_barrier_completion);
|
|
mutex_unlock(&rcu_barrier_mutex);
|
|
wait_migrated_callbacks();
|
|
}
|
|
|
|
/**
|
|
* rcu_barrier - Wait until all in-flight call_rcu() callbacks complete.
|
|
*/
|
|
void rcu_barrier(void)
|
|
{
|
|
_rcu_barrier(RCU_BARRIER_STD);
|
|
}
|
|
EXPORT_SYMBOL_GPL(rcu_barrier);
|
|
|
|
/**
|
|
* rcu_barrier_bh - Wait until all in-flight call_rcu_bh() callbacks complete.
|
|
*/
|
|
void rcu_barrier_bh(void)
|
|
{
|
|
_rcu_barrier(RCU_BARRIER_BH);
|
|
}
|
|
EXPORT_SYMBOL_GPL(rcu_barrier_bh);
|
|
|
|
/**
|
|
* rcu_barrier_sched - Wait for in-flight call_rcu_sched() callbacks.
|
|
*/
|
|
void rcu_barrier_sched(void)
|
|
{
|
|
_rcu_barrier(RCU_BARRIER_SCHED);
|
|
}
|
|
EXPORT_SYMBOL_GPL(rcu_barrier_sched);
|
|
|
|
static void rcu_migrate_callback(struct rcu_head *notused)
|
|
{
|
|
if (atomic_dec_and_test(&rcu_migrate_type_count))
|
|
wake_up(&rcu_migrate_wq);
|
|
}
|
|
|
|
extern int rcu_cpu_notify(struct notifier_block *self,
|
|
unsigned long action, void *hcpu);
|
|
|
|
static int __cpuinit rcu_barrier_cpu_hotplug(struct notifier_block *self,
|
|
unsigned long action, void *hcpu)
|
|
{
|
|
rcu_cpu_notify(self, action, hcpu);
|
|
if (action == CPU_DYING) {
|
|
/*
|
|
* preempt_disable() in on_each_cpu() prevents stop_machine(),
|
|
* so when "on_each_cpu(rcu_barrier_func, (void *)type, 1);"
|
|
* returns, all online cpus have queued rcu_barrier_func(),
|
|
* and the dead cpu(if it exist) queues rcu_migrate_callback()s.
|
|
*
|
|
* These callbacks ensure _rcu_barrier() waits for all
|
|
* RCU callbacks of the specified type to complete.
|
|
*/
|
|
atomic_set(&rcu_migrate_type_count, 3);
|
|
call_rcu_bh(rcu_migrate_head, rcu_migrate_callback);
|
|
call_rcu_sched(rcu_migrate_head + 1, rcu_migrate_callback);
|
|
call_rcu(rcu_migrate_head + 2, rcu_migrate_callback);
|
|
} else if (action == CPU_DOWN_PREPARE) {
|
|
/* Don't need to wait until next removal operation. */
|
|
/* rcu_migrate_head is protected by cpu_add_remove_lock */
|
|
wait_migrated_callbacks();
|
|
}
|
|
|
|
return NOTIFY_OK;
|
|
}
|
|
|
|
void __init rcu_init(void)
|
|
{
|
|
int i;
|
|
|
|
__rcu_init();
|
|
cpu_notifier(rcu_barrier_cpu_hotplug, 0);
|
|
|
|
/*
|
|
* We don't need protection against CPU-hotplug here because
|
|
* this is called early in boot, before either interrupts
|
|
* or the scheduler are operational.
|
|
*/
|
|
for_each_online_cpu(i)
|
|
rcu_barrier_cpu_hotplug(NULL, CPU_UP_PREPARE, (void *)(long)i);
|
|
}
|
|
|
|
void rcu_scheduler_starting(void)
|
|
{
|
|
WARN_ON(num_online_cpus() != 1);
|
|
WARN_ON(nr_context_switches() > 0);
|
|
rcu_scheduler_active = 1;
|
|
}
|