linux-kernel - Re: [PATCH 2/6] ipc/sem.c: Bugfix for semctl(,,GETZCNT)

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Date:	Tue, 13 May 2014 19:43:50 +0200
From:	Manfred Spraul <manfred@...orfullife.com>
To:	Davidlohr Bueso <davidlohr@...com>
CC:	Davidlohr Bueso <davidlohr.bueso@...com>,
	Michael Kerrisk <mtk.manpages@...il.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>, 1vier1@....de
Subject: Re: [PATCH 2/6] ipc/sem.c: Bugfix for semctl(,,GETZCNT)

Hi Davidlohr,

On 05/12/2014 08:11 PM, Davidlohr Bueso wrote:
> On Sat, 2014-05-10 at 12:03 +0200, Manfred Spraul wrote:
>> GETZCNT is supposed to return the number of threads that wait until
>> a semaphore value becomes 0.
>> The current implementation overlooks complex operations that contain
>> both wait-for-zero operation and operations that alter at least one semaphore.
> Indeed. the pending_alter list does represent blocked processes on the
> sem. Good catch. Btw, how on earth did you run into this? reading the
> code or a real case?
Reading the code.
Or more accurately:
Rewriting it, i.e. I first starting coding the new semncnt/semzcnt code, 
then I noticed that the current code is buggy.

>> The patch fixes that.
>> It's intentionally copy&paste, this will be cleaned up in the next patch.
> Instead I would have expected this patch to actually come after the
> count_* refactoring.
>
In this case:
First the bugfix, as simple as possible, then the new features.

--
     Manfred
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