From: Davidlohr Bueso <dave@stgolabs.net>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>,
Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
Manfred Spraul <manfred@colorfullife.com>,
LKML <linux-kernel@vger.kernel.org>,
Ingo Molnar <mingo@redhat.com>, Darren Hart <darren@dvhart.com>,
Steven Rostedt <rostedt@goodmis.org>,
fredrik.markstrom@windriver.com,
"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Subject: Re: [PATCH v2] ipc/mqueue: remove STATE_PENDING
Date: Tue, 28 Apr 2015 09:59:21 -0700 [thread overview]
Message-ID: <1430240361.2004.13.camel@stgolabs.net> (raw)
In-Reply-To: <20150428164329.GK5029@twins.programming.kicks-ass.net>
On Tue, 2015-04-28 at 18:43 +0200, Peter Zijlstra wrote:
> Well, if you can 'guarantee' the cmpxchg will not fail, you can then
> rely on the fact that cmpxchg implies a full barrier, which would
> obviate the need for the wmb.
Yes, assuming it implies barriers on both sides. And we could obviously
remove the need for pairing. With wake_q being local to wq_sleep() I
cannot see duplicate tasks trying to add themselves in the list. Failed
cmpxchg should only occur when users start misusing the wake_q.
Manfred, do you have any objections to this? Perhaps I've missed the
real purpose of the barriers.
Thanks,
Davidlohr
next prev parent reply other threads:[~2015-04-28 16:59 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-04-07 15:03 improve futex on -RT by avoiding the double wake-up Sebastian Andrzej Siewior
2015-04-07 15:03 ` [PATCH 1/3] futex: avoid double wake up in PI futex wait / wake on -RT Sebastian Andrzej Siewior
2015-04-07 18:41 ` Thomas Gleixner
2015-04-10 14:42 ` [PATCH 1/3 v2] " Sebastian Andrzej Siewior
2015-04-07 15:03 ` [PATCH 2/3] futex: avoid double wake up in futex_wake() " Sebastian Andrzej Siewior
2015-04-07 19:47 ` Thomas Gleixner
2015-04-10 16:11 ` [PATCH 2/3 v2] " Sebastian Andrzej Siewior
2015-04-13 3:02 ` Davidlohr Bueso
2015-04-16 5:09 ` Davidlohr Bueso
2015-04-16 9:19 ` Thomas Gleixner
2015-04-16 10:16 ` Peter Zijlstra
2015-04-16 10:49 ` Thomas Gleixner
2015-04-16 14:42 ` Davidlohr Bueso
2015-04-16 15:54 ` Peter Zijlstra
2015-04-16 16:22 ` Davidlohr Bueso
2015-04-07 15:03 ` [PATCH 3/3] ipc/mqueue: remove STATE_PENDING Sebastian Andrzej Siewior
2015-04-07 17:48 ` Manfred Spraul
2015-04-07 18:28 ` Thomas Gleixner
2015-04-10 14:37 ` [PATCH v2] " Sebastian Andrzej Siewior
2015-04-23 22:18 ` Thomas Gleixner
2015-04-28 3:24 ` Davidlohr Bueso
2015-04-28 12:37 ` Peter Zijlstra
2015-04-28 16:36 ` Davidlohr Bueso
2015-04-28 16:43 ` Peter Zijlstra
2015-04-28 16:59 ` Davidlohr Bueso [this message]
2015-04-29 19:44 ` Manfred Spraul
2015-04-30 18:46 ` Davidlohr Bueso
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