From: Peter Zijlstra <peterz@infradead.org>
To: Waiman Long <longman@redhat.com>
Cc: Ingo Molnar <mingo@redhat.com>, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v3 0/3] locking/spinlock_debug: Change it to a mostly fair lock
Date: Tue, 7 Feb 2017 09:45:53 +0100 [thread overview]
Message-ID: <20170207084553.GW6500@twins.programming.kicks-ass.net> (raw)
In-Reply-To: <1486044929-7244-1-git-send-email-longman@redhat.com>
On Thu, Feb 02, 2017 at 09:15:26AM -0500, Waiman Long wrote:
> v2->v3:
> - Keep the original v1 patches but move patch 3 of v2 in front so
> as to disable GENERIC_LOCKBREAK when DEBUG_LOCK_ALLOC is on.
>
> v1->v2:
> - Pack lockup and break_lock into a single 4-byte slot so as not
> to in increase spinlock size when GENERIC_LOCKBREAK is
> on. Hopefully that will be enough to fix a frame size too large
> warning in 0-day build.
> - Add a new patch to disable GENERIC_LOCKBREAK when DEBUG_LOCK_ALLOC
> is on.
>
> The current debug spinlock implementation is a TATAS unfair lock. This
> can occasionally lead to system lockup with a debug kernel because
> of the unfairness of the lock rather than inherent locking problem.
>
> This patch set changes the debug spinlock implementation to a
> mostly fair spinlock based on the MCS lock similar to what is done
> in qspinlock. It also includes a patch that disable GENERIC_LOCKBREAK
> when DEBUG_LOCK_ALLOC is on.
An alternative is to just delete the thing entirely..
Ingo, much of what this thing does seems to be superseded by both
lockdep and a reliable NMI watchdog. Is there still value in
spinlock_debug?
next prev parent reply other threads:[~2017-02-07 8:45 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-02-02 14:15 [PATCH v3 0/3] locking/spinlock_debug: Change it to a mostly fair lock Waiman Long
2017-02-02 14:15 ` [PATCH v3 1/3] locking/spinlock: Disable GENERIC_LOCKBREAK when DEBUG_LOCK_ALLOC is on Waiman Long
2017-02-02 14:15 ` [PATCH v3 2/3] locking/spinlock_debug: Reduce lockup suspected message clutter Waiman Long
2017-02-02 14:15 ` [PATCH v3 3/3] locking/spinlock_debug: Reduce lock cacheline contention Waiman Long
2017-02-07 8:45 ` Peter Zijlstra [this message]
2017-02-07 9:48 ` [PATCH v3 0/3] locking/spinlock_debug: Change it to a mostly fair lock Ingo Molnar
2017-02-07 19:46 ` Waiman Long
2017-02-07 19:53 ` Paul E. McKenney
2017-02-08 9:27 ` Peter Zijlstra
2017-02-08 13:02 ` Paul E. McKenney
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