Messages in this thread | | | Date | Fri, 7 Nov 2008 17:21:01 +0100 | From | Ingo Molnar <> | Subject | Re: [PATCH] account_group_exec_runtime: fix the racy usage of ->signal |
| |
* Oleg Nesterov <oleg@redhat.com> wrote:
> Compile tested. > > Unlike other similar routines, account_group_exec_runtime() could be > called "implicitly" after exit_notify(). This means we can race with > the parent doing release_task(), we can't just check ->signal != NULL. > > Take ->siglock to make sure ->signal can't go away. > > This is the minimal fix, with this patch we don't need need get/put cpu, > and I think we should uninline this function. > > Signed-off-by: Oleg Nesterov <oleg@redhat.com>
> > --- 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: the signal lock must not nest inside the rq lock, and these accounting functions are called from within the scheduler.
Ingo
| |