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From: Srivatsa Vaddagiri <vatsa@in.ibm.com>
To: "Paul Menage" <menage@google.com>
Cc: "Paul Jackson" <pj@sgi.com>,
	akpm@linux-foundation.org, dev@sw.ru, xemul@sw.ru,
	serue@us.ibm.com, ebiederm@xmission.com, haveblue@us.ibm.com,
	svaidy@linux.vnet.ibm.com, balbir@in.ibm.com,
	ckrm-tech@lists.sourceforge.net, linux-kernel@vger.kernel.org,
	rohitseth@google.com, mbligh@google.com,
	containers@lists.osdl.org, devel@openvz.org
Subject: Re: [PATCH 0/9] Containers (V9): Generic Process Containers
Date: Mon, 30 Apr 2007 23:36:53 +0530	[thread overview]
Message-ID: <20070430180653.GA31001@in.ibm.com> (raw)
In-Reply-To: <6599ad830704301009k11100a78we98e20deba9b1fdc@mail.gmail.com>

On Mon, Apr 30, 2007 at 10:09:38AM -0700, Paul Menage wrote:
> Paul, is there any reason why we need to do a write_lock() on
> tasklist_lock if we're just trying to block fork, or is it just
> historical accident? Wouldn't it be fine to do a read_lock()?

Good point ..read_lock() will probably suffice in update_nodemask which
means we don't need the patch I sent earlier.

Paul (Jackson),
	This made me see another race in update_nodemask vs fork:

Lets say cpuset CS1 has only one task T1 to begin with.

update_nodemask(CS1)			T1 in do_fork()
	CPU0				     CPU1
=============================================================


					cpuset_fork();
					mpol_copy();


ntasks = atomic_read(&cs->count);
[ntasks = 2, accounting new born child T2]
cs->mems_allowed = something;
set_cpuset_being_rebound()


write/read_lock(tasklist_lock);


do_each_thread {

	/* Finds only T1 */

	mmarray[] = ..

} while_each_thread();

write/read_unlock(tasklist_lock);

					write_lock(tasklist_lock);

					/* Add T2, child of T1 to tasklist */

					write_unlock(tasklist_lock);


for (i = 0; i < n; i++) {

	mpol_rebind_mm(..);

}


In this for loop, we migrate only T1's ->mm. T2's->mm isn't migrated
AFAICS.

Is that fine?

-- 
Regards,
vatsa

  reply	other threads:[~2007-04-30 17:58 UTC|newest]

Thread overview: 36+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2007-04-27 10:46 menage
2007-04-27 10:46 ` [PATCH 1/9] Containers (V9): Basic container framework menage
2007-04-29  3:12   ` [ckrm-tech] " Paul Jackson
2007-05-01 17:40   ` Balbir Singh
2007-05-01 17:46     ` Paul Menage
2007-05-01 18:40     ` [ckrm-tech] " Paul Jackson
2007-05-02  3:44       ` Balbir Singh
2007-05-02  6:12         ` Paul Jackson
2007-05-10  4:09           ` Balbir Singh
2007-05-10  4:47             ` Paul Jackson
2007-05-10  4:49               ` Balbir Singh
2007-04-27 10:46 ` [PATCH 2/9] Containers (V9): Example CPU accounting subsystem menage
2007-05-01 17:52   ` Balbir Singh
2007-04-27 10:46 ` [PATCH 3/9] Containers (V9): Add tasks file interface menage
2007-05-01 18:12   ` Balbir Singh
2007-05-01 20:37     ` [ckrm-tech] " Paul Menage
2007-05-02  3:25       ` Srivatsa Vaddagiri
2007-05-02  3:25         ` Paul Menage
2007-05-02  3:46           ` Srivatsa Vaddagiri
2007-05-08 14:51           ` Balbir Singh
2007-05-10 21:21             ` Paul Menage
2007-05-11  2:31               ` Balbir Singh
2007-05-02  3:58       ` Balbir Singh
2007-04-27 10:46 ` [PATCH 4/9] Containers (V9): Add fork/exit hooks menage
2007-04-27 10:46 ` [PATCH 5/9] Containers (V9): Add container_clone() interface menage
2007-04-27 10:46 ` [PATCH 6/9] Containers (V9): Add procfs interface menage
2007-04-27 10:46 ` [PATCH 7/9] Containers (V9): Make cpusets a client of containers menage
2007-04-27 10:46 ` [PATCH 8/9] Containers (V9): Share css_group arrays between tasks with same container memberships menage
2007-04-27 10:46 ` [PATCH 9/9] Containers (V9): Simple debug info subsystem menage
2007-04-29  1:47 ` [PATCH 0/9] Containers (V9): Generic Process Containers Paul Jackson
2007-04-29  9:37 ` Paul Jackson
2007-04-30 17:12   ` Srivatsa Vaddagiri
2007-04-30 17:09     ` Paul Menage
2007-04-30 18:06       ` Srivatsa Vaddagiri [this message]
2007-04-30 17:23     ` Christoph Hellwig
2007-04-30 18:16       ` [ckrm-tech] " Srivatsa Vaddagiri

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