From: Peter Zijlstra <peterz@infradead.org>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: "chengjian (D)" <cj.chengjian@huawei.com>,
huawei.libin@huawei.com, mingo@redhat.com, dvhart@infradead.org,
linux-kernel@vger.kernel.org
Subject: Re: a competition when some threads acquire futex
Date: Wed, 6 Sep 2017 11:06:31 +0200 [thread overview]
Message-ID: <20170906090631.tcer7olhogwxfrlh@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20170906085608.ogz4jhv2pieybzob@hirez.programming.kicks-ass.net>
On Wed, Sep 06, 2017 at 10:56:08AM +0200, Peter Zijlstra wrote:
> Right, but even if it was a coherent patch, I'm not sure it makes sense.
>
> futex_wait() / futex_wake() don't make ordering guarantees and in
> general you don't get to have wakeup preemption if you don't run a
> PREEMPT kernel.
>
> So what makes this wakeup so special? Any changelog would need to have a
> convincing argument.
Also, even on !PREEMPT, if that wakeup sets NEED_RESCHED, the return to
userspace after futex_wake() should reschedule.
So I'm really not getting it.
next prev parent reply other threads:[~2017-09-06 9:06 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-09-05 1:50 chengjian (D)
2017-09-05 19:37 ` Thomas Gleixner
2017-09-06 0:27 ` chengjian (D)
2017-09-06 8:36 ` Thomas Gleixner
2017-09-06 8:56 ` Peter Zijlstra
2017-09-06 9:06 ` Peter Zijlstra [this message]
2017-09-06 9:09 ` chengjian (D)
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