Brice Goglin <[email protected]> wrote:
>
> I was seeing a lockup with several -mm releases since 2.6.12-rc2-mm1
> (IIRC). With 2.6.12-rc2-mm1, I remember getting the lockup a few minutes
> after boot time.
> With 2.6.12-rc3-mm1, I waited several days before getting it.
> But, I finally caught this one with netconsole. So here it is:
>
> BUG: soft lockup detected on CPU#0!
> Pid: 0, comm: swapper
> EIP: 0060:[<c02d40a5>] CPU: 0
> EIP is at _spin_unlock_irqrestore+0x5/0x30
> EFLAGS: 00000286 Not tainted (2.6.12-rc3-mm1=Pignouf)
> EAX: c18e8160 EBX: c18e8160 ECX: 00000001 EDX: 00000286
> ESI: c18e0160 EDI: dbf96c64 EBP: ffffffff DS: 007b ES: 007b
> CR0: 8005003b CR2: b6e43000 CR3: 0e912000 CR4: 00000690
> [<c012a635>] __mod_timer+0xc5/0xf0
It could be the timer bug. Can you try it with Oleg's fix?
From: Oleg Nesterov <[email protected]>
The bug was identified by Maneesh Soni.
When __mod_timer() changes timer's base it waits for the completion of
timer->function. It is just stupid: the caller of __mod_timer() can held
locks which would prevent completion of the timer's handler.
Solution: do not change the base of the currently running timer.
Side effect: __mod_timer() doesn't garantees anymore that timer will run on
the local cpu.
Signed-off-by: Oleg Nesterov <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
---
kernel/timer.c | 42 ++++++++++++++++++++----------------------
1 files changed, 20 insertions(+), 22 deletions(-)
diff -puN kernel/timer.c~timers-fix-__mod_timer-vs-__run_timers-deadlock kernel/timer.c
--- 25/kernel/timer.c~timers-fix-__mod_timer-vs-__run_timers-deadlock 2005-05-01 02:20:28.415889280 -0700
+++ 25-akpm/kernel/timer.c 2005-05-01 02:20:28.420888520 -0700
@@ -211,41 +211,39 @@ int __mod_timer(struct timer_list *timer
timer_base_t *base;
tvec_base_t *new_base;
unsigned long flags;
- int ret = -1;
+ int ret;
BUG_ON(!timer->function);
check_timer(timer);
- do {
- base = lock_timer_base(timer, &flags);
- new_base = &__get_cpu_var(tvec_bases);
+ base = lock_timer_base(timer, &flags);
- /* Ensure the timer is serialized. */
- if (base != &new_base->t_base
- && base->running_timer == timer)
- goto unlock;
+ ret = 0;
+ if (timer_pending(timer)) {
+ detach_timer(timer, 0);
+ ret = 1;
+ }
- ret = 0;
- if (timer_pending(timer)) {
- detach_timer(timer, 0);
- ret = 1;
- }
+ new_base = &__get_cpu_var(tvec_bases);
- if (base != &new_base->t_base) {
+ if (base != &new_base->t_base) {
+ if (unlikely(base->running_timer == timer))
+ /* Don't change timer's base while it is running.
+ * Needed for serialization of timer wrt itself. */
+ new_base = container_of(base, tvec_base_t, t_base);
+ else {
timer->base = NULL;
/* Safe: the timer can't be seen via ->entry,
* and lock_timer_base checks ->base != 0. */
spin_unlock(&base->lock);
- base = &new_base->t_base;
- spin_lock(&base->lock);
- timer->base = base;
+ spin_lock(&new_base->t_base.lock);
+ timer->base = &new_base->t_base;
}
+ }
- timer->expires = expires;
- internal_add_timer(new_base, timer);
-unlock:
- spin_unlock_irqrestore(&base->lock, flags);
- } while (ret < 0);
+ timer->expires = expires;
+ internal_add_timer(new_base, timer);
+ spin_unlock_irqrestore(&new_base->t_base.lock, flags);
return ret;
}
_
-
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