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Date: Wed, 10 Apr 2013 12:51:15 +0200 (CEST) From: Thomas Gleixner <tglx@...utronix.de> To: Dave Hansen <dave@...1.net> cc: Borislav Petkov <bp@...en8.de>, "Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com>, LKML <linux-kernel@...r.kernel.org>, Dave Jones <davej@...hat.com>, dhillf@...il.com, Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...nel.org> Subject: Re: [PATCH] kthread: Prevent unpark race which puts threads on the wrong cpu On Wed, 10 Apr 2013, Thomas Gleixner wrote: > On Tue, 9 Apr 2013, Dave Hansen wrote: > > > On 04/09/2013 12:30 PM, Thomas Gleixner wrote: > > > On Tue, 9 Apr 2013, Thomas Gleixner wrote: > > > Thought more about it and found, that the stupid binding only works > > > when the task is really descheduled. So there is a small window left, > > > which could lead to this. Revised patch below. > > > > > > Anyway a trace for that issue would be appreciated nevertheless. > > > > Here you go: > > > > http://sr71.net/~dave/linux/bigbox.1365539189.txt.gz > > Hmm. Unfortunately migration/146 is not in the trace. > > Can you please apply the patch below? That avoids the oops, but might > hang an online operation. Though the machine should stay up and you > should be able to retrieve the trace. > > Thanks, > > tglx > --- > Index: linux-2.6/kernel/smpboot.c > =================================================================== > --- linux-2.6.orig/kernel/smpboot.c > +++ linux-2.6/kernel/smpboot.c > @@ -131,7 +131,10 @@ static int smpboot_thread_fn(void *data) > continue; > } > > - BUG_ON(td->cpu != smp_processor_id()); > + if (td->cpu != smp_processor_id()) { > + tracing_off(); > + schedule(); Bah, that wants a continue. Revised patch below. > + } > > /* Check for state change setup */ > switch (td->status) { Index: linux-2.6/kernel/smpboot.c =================================================================== --- linux-2.6.orig/kernel/smpboot.c +++ linux-2.6/kernel/smpboot.c @@ -131,7 +131,11 @@ static int smpboot_thread_fn(void *data) continue; } - BUG_ON(td->cpu != smp_processor_id()); + if (td->cpu != smp_processor_id()) { + tracing_off(); + schedule(); + continue; + } /* Check for state change setup */ switch (td->status) { -- 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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