linux-kernel - Re: [PATCH] ipc/sem.c: fix update sem_otime when calling sem

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Message-ID: <52429591.9080701@gmail.com>
Date:	Wed, 25 Sep 2013 15:49:37 +0800
From:	Jia He <jiakernel@...il.com>
To:	Manfred Spraul <manfred@...orfullife.com>
CC:	Mike Galbraith <bitbucket@...ine.de>, linux-kernel@...r.kernel.org,
	Davidlohr Bueso <davidlohr.bueso@...com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Rik van Riel <riel@...hat.com>,
	Al Viro <viro@...iv.linux.org.uk>
Subject: Re: [PATCH] ipc/sem.c: fix update sem_otime when calling sem_op in
 semaphore initialization

 
Hi Manfred
got it :) I am so glad that my minor is on top of yours
Anyway,
Do you think it is more safe to update the otime like this:

-      sma->sem_base[sops[0].sem_num].sem_otime =
-                                get_seconds();
+        if (sops == NULL) {
+            sma->sem_base[0].sem_otime = get_seconds();
+        } else {
+            sma->sem_base[sops[0].sem_num].sem_otime =
+                                get_seconds();
+        }

If u think so, i will update my patch according to it

On Wed, 25 Sep 2013 08:55:16 +0200 from manfred@...orfullife.com wrote:
> Hi Jia,
>
> On 09/25/2013 05:05 AM, Jia He wrote:
>>   Hi Manfred
>> IIUC after reivewing your patch and src code, does it seem
>> sem_otime lost the chance to be updated when calling
>> semctl_main/semctl_setval?
>> In old codes, even whendo_smart_update(sma, NULL, 0, 0, &tasks),
>> the otime can be updated after several conditions checking.
> The update is performed now performed inside perform_atomic_semop():
>
> Old code:
> perform_atomic_semop() does not update sem_otime. It just returns 0 for
> successfull operations.
> This "0 returned" is passed upwards ("semop_completed") into do_smart_update()
> do_smart_update() updates sem_otime.
>
> New code:
> perform_atomic_semop() updates sem_otime immediately (your change).
> No need to keep track if a waiting operation was completed (my change).
>
> I don't see a problem - perhaps I overlook something.
> Which problem do you see?
>
> -- 
>     Manfred
>
>

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