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From: Peter Zijlstra <peterz@infradead.org>
To: Jason Low <jason.low2@hp.com>
Cc: mingo@redhat.com, paulmck@linux.vnet.ibm.com, Waiman.Long@hp.com,
	torvalds@linux-foundation.org, tglx@linutronix.de,
	linux-kernel@vger.kernel.org, riel@redhat.com,
	akpm@linux-foundation.org, davidlohr@hp.com, hpa@zytor.com,
	andi@firstfloor.org, aswin@hp.com, scott.norton@hp.com,
	chegu_vinod@hp.com
Subject: Re: [RFC][PATCH v2 4/5] mutex: Disable preemtion between modifying lock->owner and locking/unlocking mutex
Date: Tue, 28 Jan 2014 21:54:06 +0100	[thread overview]
Message-ID: <20140128205406.GI11314@laptop.programming.kicks-ass.net> (raw)
In-Reply-To: <1390936396-3962-5-git-send-email-jason.low2@hp.com>

On Tue, Jan 28, 2014 at 11:13:15AM -0800, Jason Low wrote:
> This RFC patch disables preemption between modifying lock->owner and
> locking/unlocking the mutex lock. This prevents situations where the owner
> can preempt between those 2 operations, which causes optimistic spinners to
> be unable to check if lock->owner is not on CPU. As mentioned in the
> thread for this v1 patchset, disabling preemption is a cheap operation.

In that same thread it was also said that this wasn't really an issue at
all. So what is the justification?

The patch is rather hideous.

  reply	other threads:[~2014-01-28 20:54 UTC|newest]

Thread overview: 50+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-01-28 19:13 [PATCH v2 0/5] mutex: Mutex scalability patches Jason Low
2014-01-28 19:13 ` [PATCH v2 1/5] mutex: In mutex_can_spin_on_owner(), return false if task need_resched() Jason Low
2014-01-28 20:20   ` Paul E. McKenney
2014-01-28 22:01     ` Jason Low
2014-01-28 21:09   ` Davidlohr Bueso
2014-03-11 12:41   ` [tip:core/locking] locking/mutexes: Return false if task need_resched() in mutex_can_spin_on_owner() tip-bot for Jason Low
2014-01-28 19:13 ` [PATCH v2 2/5] mutex: Modify the way optimistic spinners are queued Jason Low
2014-01-28 20:23   ` Paul E. McKenney
2014-01-28 20:24     ` Paul E. McKenney
2014-01-28 21:17     ` Davidlohr Bueso
2014-01-28 22:10     ` Jason Low
2014-02-02 21:58       ` Paul E. McKenney
2014-03-11 12:41   ` [tip:core/locking] locking/mutexes: " tip-bot for Jason Low
2014-03-11 15:24     ` Jason Low
2014-03-11 15:33       ` Peter Zijlstra
2014-01-28 19:13 ` [PATCH v2 3/5] mutex: Unlock the mutex without the wait_lock Jason Low
2014-03-11 12:41   ` [tip:core/locking] locking/mutexes: " tip-bot for Jason Low
2014-03-12 12:24     ` Peter Zijlstra
2014-03-12 18:44       ` Jason Low
2014-03-13  7:28       ` [tip:core/locking] locking/mutex: Fix debug checks tip-bot for Peter Zijlstra
2014-01-28 19:13 ` [RFC][PATCH v2 4/5] mutex: Disable preemtion between modifying lock->owner and locking/unlocking mutex Jason Low
2014-01-28 20:54   ` Peter Zijlstra [this message]
2014-01-28 22:17     ` Jason Low
2014-01-28 19:13 ` [RFC][PATCH v2 5/5] mutex: Give spinners a chance to spin_on_owner if need_resched() triggered while queued Jason Low
2014-01-28 21:07   ` Peter Zijlstra
2014-01-28 22:51     ` Jason Low
2014-01-29 11:51       ` Peter Zijlstra
2014-01-31  3:29         ` Jason Low
2014-01-31 14:09           ` Peter Zijlstra
2014-01-31 20:01             ` Jason Low
2014-01-31 20:08               ` Peter Zijlstra
2014-02-02 21:01                 ` Jason Low
2014-02-02 21:12                   ` Peter Zijlstra
2014-02-03 18:39                     ` Jason Low
2014-02-03 19:25                       ` Peter Zijlstra
2014-02-03 20:55                         ` Jason Low
2014-02-03 21:06                           ` Peter Zijlstra
2014-02-03 21:56                             ` Jason Low
2014-02-04  7:13                         ` Jason Low
2014-02-02 22:02                 ` Paul E. McKenney
2014-02-02 20:02             ` Peter Zijlstra
2014-02-05 21:44         ` Waiman Long
2014-02-06 14:04           ` Peter Zijlstra
2014-02-06 18:45             ` Waiman Long
2014-02-06 20:10               ` Norton, Scott J
2014-02-10 17:01                 ` Peter Zijlstra
2014-02-06 17:44           ` Jason Low
2014-02-06 18:37             ` Waiman Long
2014-01-28 21:08 ` [PATCH v2 0/5] mutex: Mutex scalability patches Davidlohr Bueso
2014-01-28 23:11   ` Jason Low

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