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Date: Wed, 19 Feb 2014 17:16:57 +0100 From: Peter Zijlstra <peterz@...radead.org> To: Michael wang <wangyun@...ux.vnet.ibm.com> Cc: Sasha Levin <sasha.levin@...cle.com>, Ingo Molnar <mingo@...nel.org>, Dave Jones <davej@...hat.com>, LKML <linux-kernel@...r.kernel.org> Subject: Re: sched: fair: NULL ptr deref in check_preempt_wakeup On Mon, Feb 17, 2014 at 04:11:09PM +0800, Michael wang wrote: > > While fuzzing with trinity inside a KVM tools guest running latest -next > > kernel, I've > > stumbled on the following: > > I've reproduced the same issue with tip/master, and below patch fixed the > problem on my box along with some rcu stall info disappeared, would you > like to have a try? > > BTW, I reproduced it by steps: > 1. change current to RT > 2. move to a different depth cpu-cgroup > 3. change it back to FAIR > > Seems like it was caused by that RT has no task_move_group() implemented > which could maintain depth, and that lead to a wrong depth after switched > back to FAIR... > > Regards, > Michael Wang > > > > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c > index 235cfa7..4445e56 100644 > --- a/kernel/sched/fair.c > +++ b/kernel/sched/fair.c > @@ -7317,7 +7317,11 @@ static void switched_from_fair(struct rq *rq, struct task_struct *p) > */ > static void switched_to_fair(struct rq *rq, struct task_struct *p) > { > - if (!p->se.on_rq) > + struct sched_entity *se = &p->se; > +#ifdef CONFIG_FAIR_GROUP_SCHED > + se->depth = se->parent ? se->parent->depth + 1 : 0; > +#endif > + if (!se->on_rq) > return; > > /* Michael, do you think you can send a proper patch for this? -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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