Hi Steven, On Fri, Jan 19, 2018 at 10:03:53AM -0500, Steven Rostedt wrote: > On Fri, 19 Jan 2018 14:53:05 +0530 > Pavan Kondeti <pkond...@codeaurora.org> wrote: > > > I am seeing "spinlock already unlocked" BUG for rd->rto_lock on a 4.9 > > stable kernel based system. This issue is observed only after > > inclusion of this patch. It appears to me that rq->rd can change > > between spinlock is acquired and released in rto_push_irq_work_func() > > IRQ work if hotplug is in progress. It was only reported couple of > > times during long stress testing. The issue can be easily reproduced > > if an artificial delay is introduced between lock and unlock of > > rto_lock. The rq->rd is changed under rq->lock, so we can protect this > > race with rq->lock. The below patch solved the problem. we are taking > > rq->lock in pull_rt_task()->tell_cpu_to_push(), so I extended the same > > here. Please let me know your thoughts on this. > > As so rq->rd can change. Interesting. > > > > > diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c > > index d863d39..478192b 100644 > > --- a/kernel/sched/rt.c > > +++ b/kernel/sched/rt.c > > @@ -2284,6 +2284,7 @@ void rto_push_irq_work_func(struct irq_work *work) > > raw_spin_unlock(&rq->lock); > > } > > > > + raw_spin_lock(&rq->lock); > > > What about just saving the rd then? > > struct root_domain *rd; > > rd = READ_ONCE(rq->rd); > > then use that. Then we don't need to worry about it changing. >
Yeah, it should work. I will give it a try and send the patch for review. -- Qualcomm India Private Limited, on behalf of Qualcomm Innovation Center, Inc. Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a Linux Foundation Collaborative Project.
