linux-kernel - Re: [PATCH 2/2] ipc/sem.c: move wake_up

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Message-ID: <4BEAF0FC.1000803@colorfullife.com>
Date:	Wed, 12 May 2010 20:18:36 +0200
From:	Manfred Spraul <manfred@...orfullife.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
CC:	LKML <linux-kernel@...r.kernel.org>,
	Chris Mason <chris.mason@...cle.com>,
	Zach Brown <zach.brown@...cle.com>,
	Jens Axboe <jens.axboe@...cle.com>,
	Nick Piggin <npiggin@...e.de>
Subject: Re: [PATCH 2/2] ipc/sem.c: move wake_up_process out of the spinlock
 section

On 05/12/2010 07:34 PM, Manfred Spraul wrote:
>
> The effect would be that e.g. a semctl(SETALL) operation might change 
> sem_otime.
> semctl(SETALL) must only change sem_ctime (and sem_otime only if it 
> causes a wakeup
> and the woken up thread modifies the array)
>
Just for your information: I'm not sure why semctl(SETALL) changes 
sem_ctime at all.
According to the opengroup, it shouldn't do that.

On FreeBSD, it doesn't.

Any proposals how to fix it?
Should I remove the update to sem_ctime?


 > [manfred@...es linux-2.6]$ touch ipc/sem.o
It should have been "touch ipc/sem.c":

 > [manfred@...es linux-2.6]$ touch ipc/sem.c
 > [manfred@...es linux-2.6]$ make ipc
 >   CHK     include/linux/version.h
 >   CHK     include/generated/utsrelease.h
 >  CALL    scripts/checksyscalls.sh
 >  CC      ipc/sem.o
 >  LD      ipc/built-in.o

--
     Manfred
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