From 800d4d30c8f20bd728e5741a3b77c4859a613f7c Mon Sep 17 00:00:00 2001 From: Yong Zhang Date: Sun, 20 Feb 2011 15:08:14 +0800 Subject: [PATCH] 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 Signed-off-by: Peter Zijlstra Cc: Mike Galbraith LKML-Reference: <1298185696-4403-4-git-send-email-yong.zhang0@gmail.com> Signed-off-by: Ingo Molnar --- kernel/sched_autogroup.c | 4 ++++ kernel/sched_autogroup.h | 5 +++++ 2 files changed, 9 insertions(+) diff --git a/kernel/sched_autogroup.c b/kernel/sched_autogroup.c index 9fb65628315..137a096ae9d 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 7b859ffe5da..05577055cfc 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;