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author | Oleg Nesterov <oleg@redhat.com> | 2008-11-10 14:39:30 (GMT) |
---|---|---|
committer | Ingo Molnar <mingo@elte.hu> | 2008-11-11 07:01:43 (GMT) |
commit | ad474caca3e2a0550b7ce0706527ad5ab389a4d4 (patch) | |
tree | 6d4e5cbcee3a85230317a33d66655ece0c873f5c /kernel/exit.c | |
parent | 5ac5c4d604bf894ef672a7971d03fefdc7ea7e49 (diff) | |
download | linux-fsl-qoriq-ad474caca3e2a0550b7ce0706527ad5ab389a4d4.tar.xz |
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>
Diffstat (limited to 'kernel/exit.c')
-rw-r--r-- | kernel/exit.c | 5 |
1 files changed, 5 insertions, 0 deletions
diff --git a/kernel/exit.c b/kernel/exit.c index 80137a5..ae2b92b 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); } } |