From: Oleg Nesterov <oleg@redhat.com>
To: Ingo Molnar <mingo@elte.hu>
Cc: Andrew Morton <akpm@linux-foundation.org>,
adobriyan@gmail.com, Doug Chapman <doug.chapman@hp.com>,
Peter Zijlstra <peterz@infradead.org>,
Roland McGrath <roland@redhat.com>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] account_group_exec_runtime: fix the racy usage of ->signal
Date: Fri, 7 Nov 2008 18:40:16 +0100 [thread overview]
Message-ID: <20081107174016.GA24812@redhat.com> (raw)
In-Reply-To: <20081107162101.GA2178@elte.hu>
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.
next prev parent reply other threads:[~2008-11-07 16:39 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-11-07 16:52 [PATCH] account_group_exec_runtime: fix the racy usage of ->signal Oleg Nesterov
2008-11-07 16:21 ` Ingo Molnar
2008-11-07 16:58 ` Doug Chapman
2008-11-07 18:42 ` Oleg Nesterov
2008-11-07 17:40 ` Oleg Nesterov [this message]
2008-11-08 9:28 ` Ingo Molnar
2008-11-10 13:04 ` Oleg Nesterov
2008-11-10 12:13 ` Peter Zijlstra
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