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]
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=4E97332C.8020202@colorfullife.com \
--to=manfred@colorfullife.com \
--cc=a.p.zijlstra@chello.nl \
--cc=akpm@linux-foundation.org \
--cc=efault@gmx.de \
--cc=linux-kernel@vger.kernel.org \
--cc=tglx@linutronix.de \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.