diff options
| author | Oleg Nesterov <oleg@redhat.com> | 2008-11-10 15:39:30 +0100 |
|---|---|---|
| committer | Ingo Molnar <mingo@elte.hu> | 2008-11-11 08:01:43 +0100 |
| commit | ad474caca3e2a0550b7ce0706527ad5ab389a4d4 (patch) | |
| tree | 6d4e5cbcee3a85230317a33d66655ece0c873f5c | |
| parent | 5ac5c4d604bf894ef672a7971d03fefdc7ea7e49 (diff) | |
fix for account_group_exec_runtime(), make sure ->signal can't be freed under rq->lock
Impact: fix hang/crash on ia64 under high load
This is ugly, but the simplest patch by far.
Unlike other similar routines, account_group_exec_runtime() could be
called "implicitly" from within scheduler after exit_notify(). This
means we can race with the parent doing release_task(), we can't just
check ->signal != NULL.
Change __exit_signal() to do spin_unlock_wait(&task_rq(tsk)->lock)
before __cleanup_signal() to make sure ->signal can't be freed under
task_rq(tsk)->lock. Note that task_rq_unlock_wait() doesn't care
about the case when tsk changes cpu/rq under us, this should be OK.
Thanks to Ingo who nacked my previous buggy patch.
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Reported-by: Doug Chapman <doug.chapman@hp.com>
| -rw-r--r-- | include/linux/sched.h | 1 | ||||
| -rw-r--r-- | kernel/exit.c | 5 | ||||
| -rw-r--r-- | kernel/sched.c | 8 |
3 files changed, 14 insertions, 0 deletions
diff --git a/include/linux/sched.h b/include/linux/sched.h index 295b7c756ca..644ffbda17c 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -247,6 +247,7 @@ extern void init_idle(struct task_struct *idle, int cpu); extern void init_idle_bootup_task(struct task_struct *idle); extern int runqueue_is_locked(void); +extern void task_rq_unlock_wait(struct task_struct *p); extern cpumask_t nohz_cpu_mask; #if defined(CONFIG_SMP) && defined(CONFIG_NO_HZ) diff --git a/kernel/exit.c b/kernel/exit.c index 80137a5d946..ae2b92be5fa 100644 --- a/kernel/exit.c +++ b/kernel/exit.c @@ -141,6 +141,11 @@ static void __exit_signal(struct task_struct *tsk) if (sig) { flush_sigqueue(&sig->shared_pending); taskstats_tgid_free(sig); + /* + * Make sure ->signal can't go away under rq->lock, + * see account_group_exec_runtime(). + */ + task_rq_unlock_wait(tsk); __cleanup_signal(sig); } } diff --git a/kernel/sched.c b/kernel/sched.c index f3149244e32..50a21f96467 100644 --- a/kernel/sched.c +++ b/kernel/sched.c @@ -969,6 +969,14 @@ static struct rq *task_rq_lock(struct task_struct *p, unsigned long *flags) } } +void task_rq_unlock_wait(struct task_struct *p) +{ + struct rq *rq = task_rq(p); + + smp_mb(); /* spin-unlock-wait is not a full memory barrier */ + spin_unlock_wait(&rq->lock); +} + static void __task_rq_unlock(struct rq *rq) __releases(rq->lock) { |