From: Jason Low <jason.low2@hp.com>
To: Peter Zijlstra <peterz@infradead.org>
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 14:17:49 -0800 [thread overview]
Message-ID: <1390947469.2807.33.camel@j-VirtualBox> (raw)
In-Reply-To: <20140128205406.GI11314@laptop.programming.kicks-ass.net>
On Tue, 2014-01-28 at 21:54 +0100, Peter Zijlstra wrote:
> 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?
This patch is mainly just a complementary patch for patch 5 so that we
can allow the spinner to wait slightly longer for lock->count to get set
without worrying about need_resched()/owner getting preempted.
Jason
next prev parent reply other threads:[~2014-01-28 22:17 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
2014-01-28 22:17 ` Jason Low [this message]
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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