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SubjectRe: [crash, bisected] Re: clocksource: Resolve cpu hotplug dead lock with TSC unstable

* Ingo Molnar <mingo@elte.hu> wrote:

>
> * Ingo Molnar <mingo@elte.hu> wrote:
>
> >
> > * Jens Axboe <jens.axboe@oracle.com> wrote:
> >
> > > I went to try -tip btw, but it crashes on boot. Here's the
> > > backtrace, typed manually, it's crashing in
> > > queue_work_on+0x28/0x60.
> > >
> > > Call Trace:
> > > queue_work
> > > schedule_work
> > > clocksource_mark_unstable
> > > mark_tsc_unstable
> > > check_tsc_sync_source
> > > native_cpu_up
> > > relay_hotcpu_callback
> > > do_forK_idle
> > > _cpu_up
> > > cpu_up
> > > kernel_init
> > > kernel_thread_helper
> >
> > hm, that looks like an old bug i fixed days ago via:
> >
> > 00a3273: Revert "x86: Make tsc=reliable override boot time stability checks"
> >
> > Have you tested tip:master - do you still know which sha1?
>
> Ok, i reproduced it on a testbox and bisected it, the crash is
> caused by:
>
> 7285dd7fd375763bfb8ab1ac9cf3f1206f503c16 is first bad commit
> commit 7285dd7fd375763bfb8ab1ac9cf3f1206f503c16
> Author: Thomas Gleixner <tglx@linutronix.de>
> Date: Fri Aug 28 20:25:24 2009 +0200
>
> clocksource: Resolve cpu hotplug dead lock with TSC unstable
>
> Martin Schwidefsky analyzed it:
>
> I've reverted it in tip/master for now.

and that uncovers the circular locking bug that this commit was
supposed to fix ...

Martin?

Ingo


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