Re: [PATCH] locking/spinlock_debug: Remove spinlock lockup detection code

From	Peter Zijlstra <peterz@infradead.org>
Newsgroups	linux.kernel
Subject	Re: [PATCH] locking/spinlock_debug: Remove spinlock lockup detection code
Date	2017-02-09 16:50 +0100
Message-ID	<t8Z8R-7WR-3@gated-at.bofh.it> (permalink)
References	<t8Gzg-4w9-1@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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On Wed, Feb 08, 2017 at 02:46:48PM -0500, Waiman Long wrote:
> The current spinlock lockup detection code can sometimes produce false
> positives because of the unfairness of the locking algorithm itself.

Also, __delay(1) can be really terrible, which then causes the timeout
to be highly variable and prone to triggering.

> So the lockup detection code is now removed. Instead, we are relying
> on the NMI watchdog to detect potential lockup. We won't have lockup
> detection if the watchdog isn't running.
> 
> The commented-out read-write lock lockup detection code are also
> removed.

Yes, this retains all the extra validation fields, which I've meanwhile
heard are sometimes useful but does away with all the fragile bits.

Thanks!

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[PATCH] locking/spinlock_debug: Remove spinlock lockup detection code Waiman Long <longman@redhat.com> - 2017-02-08 21:00 +0100
  Re: [PATCH] locking/spinlock_debug: Remove spinlock lockup detection  code Peter Zijlstra <peterz@infradead.org> - 2017-02-09 16:50 +0100

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