linux-kernel - Re: [PATCH] watchdog: perform all-CPU backtrace in case of hard lockup

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Date:	Thu, 1 Oct 2015 12:05:57 +0100
From:	Aaron Tomlin <atomlin@...hat.com>
To:	Jiri Kosina <jikos@...nel.org>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Ulrich Obergfell <uobergfe@...hat.com>,
	Don Zickus <dzickus@...hat.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] watchdog: perform all-CPU backtrace in case of hard
 lockup

On Thu 2015-10-01 09:45 +0200, Jiri Kosina wrote:
> That should be fine. Worst case scenario is hardlockup and softlockup 
> trigerring 'in parallel' on different CPUs, and all-cpu backtrace being 
> triggered twice.
> 
> Frankly, I've never seen this happen in practice (hardlockup and 
> softlockup triggering at different CPUs at the very same time).
> 
> We could possibly make a global 'all_cpus_dump_in_progress' flag so that 
> we guarantee only one stream of dumps, but we'd need to convert everybody 
> using this facility (e.g. RCU stall detector, and whoever else) to be 
> aware of it as well, otherwise it wouldn't make too much sense.
> 
> Something to add to TODO I guess.

This could indeed be worth further investigation.


-- 
Aaron Tomlin
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