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From: Peter Zijlstra <peterz@infradead.org>
To: Waiman Long <longman@redhat.com>
Cc: Ingo Molnar <mingo@redhat.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH] locking/spinlock_debug: Remove spinlock lockup detection code
Date: Thu, 9 Feb 2017 16:46:17 +0100	[thread overview]
Message-ID: <20170209154617.GE6515@twins.programming.kicks-ass.net> (raw)
In-Reply-To: <1486583208-11038-1-git-send-email-longman@redhat.com>

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!

      reply	other threads:[~2017-02-09 15:46 UTC|newest]

Thread overview: 2+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-02-08 19:46 Waiman Long
2017-02-09 15:46 ` Peter Zijlstra [this message]

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