Messages in this thread | | | Date | Tue, 12 Mar 2019 08:59:22 +0100 | From | luca abeni <> | Subject | Re: WARN ON at kernel/sched/deadline.c task_non_contending |
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Hi all,
On Tue, 12 Mar 2019 10:03:12 +0800 "chengjian (D)" <cj.chengjian@huawei.com> wrote:
> Hi. > > When looking to test SCHED_DEADLINE syzkaller report an warn in > task_non_contending(). I tested the mainline kernel with the C program > and captured the same call trace. [...] > diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c > index 31c050a0d0ce..d73cb033a06d 100644 > --- a/kernel/sched/deadline.c > +++ b/kernel/sched/deadline.c > @@ -252,7 +252,6 @@ static void task_non_contending(struct > task_struct *p) if (dl_entity_is_special(dl_se)) > return; > > - WARN_ON(hrtimer_active(&dl_se->inactive_timer)); > WARN_ON(dl_se->dl_non_contending); > > zerolag_time = dl_se->deadline - > @@ -287,7 +286,9 @@ static void task_non_contending(struct > task_struct *p) } > > dl_se->dl_non_contending = 1; > - get_task_struct(p); > + > + if (!hrtimer_active(&dl_se->inactive_timer)); > + get_task_struct(p); > hrtimer_start(timer, ns_to_ktime(zerolag_time), > HRTIMER_MODE_REL); }
At a first glance, I think the patch is OK, but I need some more time to look at the details.
I'll run some experiments with the reproducer, and I'll let you know my conclusions.
> Did I miss something ? > > I saw it directly remove the hrtimer in hrtime_start() if hrtime is > queued, it may be unsafe here when the timer handler is running.
This is probably why I added that WARN_ON()... I'll look at a possible solution.
Thanks, Luca
> > Help ? > > I put the syzkaller log and C demo in attachments. > > Thanks. > > >
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