lkml.org 
[lkml]   [2011]   [Feb]   [23]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Date
From
Subject[tip:sched/core] sched, autogroup: Stop going ahead if autogroup is disabled
Commit-ID:  800d4d30c8f20bd728e5741a3b77c4859a613f7c
Gitweb: http://git.kernel.org/tip/800d4d30c8f20bd728e5741a3b77c4859a613f7c
Author: Yong Zhang <yong.zhang0@gmail.com>
AuthorDate: Sun, 20 Feb 2011 15:08:14 +0800
Committer: Ingo Molnar <mingo@elte.hu>
CommitDate: Wed, 23 Feb 2011 11:33:59 +0100

sched, autogroup: Stop going ahead if autogroup is disabled

when autogroup is disable from the beginning,
sched_autogroup_create_attach()
autogroup_move_group() <== 1
sched_move_task() <== 2
task_move_group_fair()
set_task_rq()
task_group()
autogroup_task_group()

We go the whole path without doing anything useful.

Then stop going further if autogroup is disabled.

But there will be a race window between 1 and 2, in which
sysctl_sched_autogroup_enabled is enabled. This issue
will be toke by following patch.

Signed-off-by: Yong Zhang <yong.zhang0@gmail.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Mike Galbraith <efault@gmx.de>
LKML-Reference: <1298185696-4403-4-git-send-email-yong.zhang0@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
---
kernel/sched_autogroup.c | 4 ++++
kernel/sched_autogroup.h | 5 +++++
2 files changed, 9 insertions(+), 0 deletions(-)
diff --git a/kernel/sched_autogroup.c b/kernel/sched_autogroup.c
index 9fb6562..137a096 100644
--- a/kernel/sched_autogroup.c
+++ b/kernel/sched_autogroup.c
@@ -161,11 +161,15 @@ autogroup_move_group(struct task_struct *p, struct autogroup *ag)

p->signal->autogroup = autogroup_kref_get(ag);

+ if (!ACCESS_ONCE(sysctl_sched_autogroup_enabled))
+ goto out;
+
t = p;
do {
sched_move_task(t);
} while_each_thread(p, t);

+out:
unlock_task_sighand(p, &flags);
autogroup_kref_put(prev);
}
diff --git a/kernel/sched_autogroup.h b/kernel/sched_autogroup.h
index 7b859ff..0557705 100644
--- a/kernel/sched_autogroup.h
+++ b/kernel/sched_autogroup.h
@@ -1,6 +1,11 @@
#ifdef CONFIG_SCHED_AUTOGROUP

struct autogroup {
+ /*
+ * reference doesn't mean how many thread attach to this
+ * autogroup now. It just stands for the number of task
+ * could use this autogroup.
+ */
struct kref kref;
struct task_group *tg;
struct rw_semaphore lock;

\
 
 \ /
  Last update: 2011-02-23 13:09    [from the cache]
©2003-2011 Jasper Spaans