From: Manfred Spraul <manfred@colorfullife.com>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: LKML <linux-kernel@vger.kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
Mike Galbraith <efault@gmx.de>,
Peter Zijlstra <a.p.zijlstra@chello.nl>
Subject: Re: [PATCH 2/3] ipc/sem.c: handle spurious wakeups
Date: Thu, 13 Oct 2011 20:51:24 +0200 [thread overview]
Message-ID: <4E97332C.8020202@colorfullife.com> (raw)
In-Reply-To: <20111011145441.228e4c94.akpm@linux-foundation.org>
On 10/11/2011 11:54 PM, Andrew Morton wrote:
> On Sat, 24 Sep 2011 19:37:11 +0200
> Manfred Spraul<manfred@colorfullife.com> wrote:
>
>> semtimedop() does not handle spurious wakeups, it returns -EINTR to user space.
>> Most other schedule() users would just loop and not return to user space.
>> The patch adds such a loop to semtimedop()
> What is a "spurious wakeup" and how can a process receive one?
A spurious wakeup means that someone calls wake_up_process() without a
proper reason.
The most common case would be a wake_up_process() that was somehow delayed.
Peter's patch made such delayed wakeups very common, this is how we
found the issue.
The "standard" kernel primitives handle such wakeups, ipc/sem.c doesn't
handle that.
> I'm wondering about the userspace-visible effects of this change, and
> any compatibility issues?
This change has no userspace visible effects.
--
Manfred
prev parent reply other threads:[~2011-10-13 18:44 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-09-24 17:37 [PATCH 2/3] ipc/sem.c: handle spurious wakeups Manfred Spraul
2011-10-11 21:54 ` Andrew Morton
2011-10-12 7:09 ` Peter Zijlstra
2011-10-13 18:51 ` Manfred Spraul [this message]
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