Messages in this thread Patch in this message | | | Date | Fri, 7 Nov 2008 19:42:05 +0100 | From | Oleg Nesterov <> | Subject | Re: [PATCH] account_group_exec_runtime: fix the racy usage of ->signal |
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On 11/07, Doug Chapman wrote: > > On Fri, 2008-11-07 at 17:21 +0100, Ingo Molnar wrote: > > * Oleg Nesterov <oleg@redhat.com> wrote: > > > > > @@ -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. > > I can confirm that this does hang on bootup.
Thanks a lot Doug.
If only I could understand what happens. I am running the 2.6.27 kernel with the patch below just fine.
Ingo, could you please explain?
OK, perhaps we can check ->exit_state... I'll return on Monday.
--- linux-2.6.27/kernel/sched_fair.c~DBG 2008-10-10 00:13:53.000000000 +0200 +++ linux-2.6.27/kernel/sched_fair.c 2008-11-07 19:15:28.000000000 +0100 @@ -484,6 +484,16 @@ __update_curr(struct cfs_rq *cfs_rq, str curr->vruntime += delta_exec_weighted; } +static void ttt(struct task_struct *tsk) +{ + unsigned long flags; + + if (unlikely(!lock_task_sighand(tsk, &flags))) + return; + + unlock_task_sighand(tsk, &flags); +} + static void update_curr(struct cfs_rq *cfs_rq) { struct sched_entity *curr = cfs_rq->curr; @@ -507,6 +517,7 @@ static void update_curr(struct cfs_rq *c struct task_struct *curtask = task_of(curr); cpuacct_charge(curtask, delta_exec); + ttt(curtask); } }
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