linux-kernel - [PATCH] task containersv11 add tasks file interface fix for cpusets

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Date:	Wed, 03 Oct 2007 01:42:41 -0700
From:	Paul Jackson <pj@....com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Nick Piggin <nickpiggin@...oo.com.au>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	"Serge E. Hallyn" <serue@...ibm.com>,
	Cedric Le Goater <clg@...ibm.com>,
	Paul Menage <menage@...gle.com>, linux-kernel@...r.kernel.org,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	David Rientjes <rientjes@...gle.com>,
	Vaidyanathan Srinivasan <svaidy@...ux.vnet.ibm.com>,
	Pavel Emelianov <xemul@...nvz.org>, containers@...ts.osdl.org,
	Paul Jackson <pj@....com>, balbir@...ux.vnet.ibm.com
Subject: [PATCH] task containersv11 add tasks file interface fix for cpusets

From: Paul Jackson <pj@....com>

The code in kernel/cgroup.c attach_task() which skips the
attachment of a task to the group it is already in has to be
removed.  Cpusets depends on reattaching a task to its current
cpuset, in order to trigger updating the cpus_allowed mask in the
task struct.

The dependency of cpusets on this is a hack, granted, but an
important one.  It lets us avoid checking for a changed cpuset
'cpus' setting in critical scheduler code paths.

Signed-off-by: Paul Jackson <pj@....com>
Cc: Paul Menage <menage@...gle.com>

---

Andrew - this patch applies directly following the patch:
    task-containersv11-add-tasks-file-interface.patch

 kernel/cgroup.c |    3 ---
 1 file changed, 3 deletions(-)

--- 2.6.23-rc8-mm1.orig/kernel/cgroup.c	2007-10-02 20:24:11.078925442 -0700
+++ 2.6.23-rc8-mm1/kernel/cgroup.c	2007-10-02 20:25:41.352279374 -0700
@@ -739,10 +739,7 @@ static int attach_task(struct cgroup *co
 
 	get_first_subsys(cont, NULL, &subsys_id);
 
-	/* Nothing to do if the task is already in that cgroup */
 	oldcont = task_cgroup(tsk, subsys_id);
-	if (cont == oldcont)
-		return 0;
 
 	for_each_subsys(root, ss) {
 		if (ss->can_attach) {

-- 
                          I won't rest till it's the best ...
                          Programmer, Linux Scalability
                          Paul Jackson <pj@....com> 1.650.933.1373
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