Messages in this thread | | | Date | Fri, 7 Nov 2008 18:40:16 +0100 | From | Oleg Nesterov <> | Subject | Re: [PATCH] account_group_exec_runtime: fix the racy usage of ->signal |
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On 11/07, Ingo Molnar wrote: > > * Oleg Nesterov <oleg@redhat.com> wrote: > > > --- K-28/kernel/sched_stats.h~A_G_E_R_FIX 2008-11-07 17:32:02.000000000 +0100 > > +++ K-28/kernel/sched_stats.h 2008-11-07 17:44:39.000000000 +0100 > > @@ -351,10 +351,12 @@ static inline void account_group_exec_ru > > unsigned long long ns) > > { > > struct signal_struct *sig; > > + unsigned long flags; > > > > - sig = tsk->signal; > > - if (unlikely(!sig)) > > + if (unlikely(!lock_task_sighand(tsk, &flags))) > > return; > > i think this will lock up:
Ah. I worried about this, but convinced myself this is OK...
> the signal lock must not nest inside the rq > lock, and these accounting functions are called from within the > scheduler.
Why? we seem to never do task_rq_lock() under ->siglock ?
Oleg.
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