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Date: Wed, 10 Nov 2010 11:05:16 -0500 From: Don Zickus <dzickus@...hat.com> To: Ingo Molnar <mingo@...e.hu> Cc: fweisbec@...il.com, Peter Zijlstra <peterz@...radead.org>, LKML <linux-kernel@...r.kernel.org>, akpm@...ux-foundation.org, sergey.senozhatsky@...il.com Subject: Re: [PATCH v3] watchdog: touch_nmi_watchdog should only touch local cpu not every one On Wed, Nov 10, 2010 at 08:49:41AM +0100, Ingo Molnar wrote: > > * Don Zickus <dzickus@...hat.com> wrote: > > > I ran into a scenario where while one cpu was stuck and should have panic'd > > because of the NMI watchdog, it didn't. The reason was another cpu was spewing > > stack dumps on to the console. Upon investigation, I noticed that when writing to > > the console and also when dumping the stack, the watchdog is touched. > > > > This causes all the cpus to reset their NMI watchdog flags and the 'stuck' cpu > > just spins forever. > > Hm, the flip side is that if a CPU is stuck spewing backtraces, we will now make all > the other CPUs a lot more noisy - which might only 'lock up' because this CPU is > stuck spewing oopses, right? When you say the other CPUs will be a lot more noisy, is that because they are busy processing backtraces for the first cpu to spew? I guess I don't understand how the other CPUs could have their interrupts off the whole time while the first cpu is spewing a backtrace (just trying to educate myself). Cheers, Don -- 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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