From: Jia He <jiakernel@gmail.com>
To: Mike Galbraith <bitbucket@online.de>,
Manfred Spraul <manfred@colorfullife.com>
Cc: linux-kernel@vger.kernel.org,
Davidlohr Bueso <davidlohr.bueso@hp.com>,
Andrew Morton <akpm@linux-foundation.org>,
Rik van Riel <riel@redhat.com>, Al Viro <viro@zeniv.linux.org.uk>
Subject: Re: [PATCH] ipc/sem.c: fix update sem_otime when calling sem_op in semaphore initialization
Date: Mon, 23 Sep 2013 10:24:36 +0800 [thread overview]
Message-ID: <523FA664.2070101@gmail.com> (raw)
In-Reply-To: <1379898516.5476.27.camel@marge.simpson.net>
On Mon, 23 Sep 2013 03:08:36 +0200 from bitbucket@online.de wrote:
> On Sun, 2013-09-22 at 12:42 +0200, Manfred Spraul wrote:
>
>> Mike: no, your patch makes it worse:
>> - wait-for-zero semops still don't update sem_otime
>> - sem_otime is initialized to sem_ctime. That's not mentioned in the
>> sysv standard.
> So sem_otime = 0 is a specified semaphore state? I thought the proggy
> was busted for spinning on a (busted and) irrelevant stamp.
Please refer to the words from Unix Network Programming - Volume 2 2nd
Edition Chapter 11
"Fortunately, there is a way around this race condition. We are guaranteed
that thesem-otime member of the semid-ds structure is set to 0 when a
new semaphore set iscreated. (The System V manuals have stated this
fact for a long time, as do the XPG3and Unix 98 standards.) This member
is set to the current time only by a successful callto semop."
>
> Man lernt nie aus.
>
> -Mike
>
>
prev parent reply other threads:[~2013-09-23 2:24 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-09-22 2:11 [PATCH] ipc/sem.c: fix update sem_otime when calling sem_op in semaphore initialization Jia He
2013-09-22 8:17 ` Mike Galbraith
2013-09-22 8:26 ` Mike Galbraith
2013-09-22 9:34 ` Jia He
2013-09-22 10:00 ` Mike Galbraith
2013-09-22 12:44 ` Jia He
2013-09-22 10:42 ` Manfred Spraul
2013-09-22 12:53 ` Jia He
2013-09-22 15:14 ` Jia He
2013-09-24 21:09 ` Manfred Spraul
2013-09-25 3:05 ` Jia He
2013-09-25 6:55 ` Manfred Spraul
2013-09-25 7:49 ` Jia He
2013-09-23 1:08 ` Mike Galbraith
2013-09-23 2:24 ` Jia He [this message]
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