From: Peter Zijlstra <peterz@infradead.org>
To: will.deacon@arm.com, mingo@kernel.org
Cc: linux-kernel@vger.kernel.org, longman@redhat.com,
andrea.parri@amarulasolutions.com, tglx@linutronix.de,
Peter Zijlstra <peterz@infradead.org>
Subject: [RFC][PATCH 0/3] locking/qspinlock: Improve determinism for x86
Date: Wed, 26 Sep 2018 13:01:17 +0200 [thread overview]
Message-ID: <20180926110117.405325143@infradead.org> (raw)
Back when Will did his qspinlock determinism patches, we were left with one
cmpxchg loop on x86 due to the use of atomic_fetch_or(). Will proposed a nifty
trick:
http://lkml.kernel.org/r/20180409145409.GA9661@arm.com
But at the time we didn't pursue it. This series implements that and argues for
its correctness. In particular it places an smp_mb__after_atomic() in
between the two operations, which forces the load to come after the
store (which is free on x86 anyway).
In particular this ordering ensures a concurrent unlock cannot trigger
the uncontended handoff. Also it ensures that if the xchg() happens
after a (successful) trylock, we must observe that LOCKED bit.
next reply other threads:[~2018-09-26 11:30 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-09-26 11:01 Peter Zijlstra [this message]
2018-09-26 11:01 ` [RFC][PATCH 1/3] locking/qspinlock: Re-order code Peter Zijlstra
2018-10-01 17:17 ` Will Deacon
2018-09-26 11:01 ` [RFC][PATCH 2/3] locking/qspinlock: Rework some comments Peter Zijlstra
2018-10-01 17:17 ` Will Deacon
2018-10-01 19:10 ` Peter Zijlstra
2018-10-02 13:20 ` Will Deacon
2018-10-02 13:43 ` Peter Zijlstra
2018-09-26 11:01 ` [RFC][PATCH 3/3] locking/qspinlock: Optimize for x86 Peter Zijlstra
2018-09-26 16:30 ` Waiman Long
2018-09-26 17:54 ` Peter Zijlstra
2018-09-27 7:29 ` Peter Zijlstra
2018-09-26 20:52 ` Andrea Parri
2018-09-27 7:17 ` Peter Zijlstra
2018-09-27 7:47 ` Andrea Parri
2018-09-27 7:59 ` Peter Zijlstra
2018-09-27 8:13 ` Andrea Parri
2018-09-27 8:57 ` Peter Zijlstra
2018-09-27 12:16 ` David Laight
2018-10-01 17:17 ` Will Deacon
2018-10-01 20:00 ` Peter Zijlstra
2018-10-02 13:19 ` Will Deacon
2018-10-02 14:14 ` Peter Zijlstra
2018-10-02 12:31 ` Andrea Parri
2018-10-02 13:22 ` Will Deacon
2018-10-02 13:44 ` Andrea Parri
2018-09-26 15:01 ` [RFC][PATCH 0/3] locking/qspinlock: Improve determinism " Sebastian Andrzej Siewior
2018-09-26 15:08 ` Thomas Gleixner
2018-09-26 15:38 ` Sebastian Andrzej Siewior
2018-09-26 16:20 ` Waiman Long
2018-09-26 17:51 ` Peter Zijlstra
2018-09-26 23:21 ` Waiman Long
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