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authorKirill Tkhai <ktkhai@parallels.com>2014-10-28 08:24:34 +0300
committerIngo Molnar <mingo@kernel.org>2014-11-04 07:07:30 +0100
commitf7b8a47da17c9ee4998f2ca2018fcc424e953c0e (patch)
tree90a76aa80a49f4a93b1dc162a26323f4661e893d /kernel
parent980d0d51b1c9617a472b2c0fcbe33d2d15eadc4c (diff)
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sched: Remove lockdep check in sched_move_task()
sched_move_task() is the only interface to change sched_task_group: cpu_cgrp_subsys methods and autogroup_move_group() use it. Everything is synchronized by task_rq_lock(), so cpu_cgroup_attach() is ordered with other users of sched_move_task(). This means we do no need RCU here: if we've dereferenced a tg here, the .attach method hasn't been called for it yet. Thus, we should pass "true" to task_css_check() to silence lockdep warnings. Fixes: eeb61e53ea19 ("sched: Fix race between task_group and sched_task_group") Reported-by: Oleg Nesterov <oleg@redhat.com> Reported-by: Fengguang Wu <fengguang.wu@intel.com> Signed-off-by: Kirill Tkhai <ktkhai@parallels.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Link: http://lkml.kernel.org/r/1414473874.8574.2.camel@tkhai Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/sched/core.c8
1 files changed, 6 insertions, 2 deletions
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 240157c13ddc..6841fb46eb07 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -7444,8 +7444,12 @@ void sched_move_task(struct task_struct *tsk)
if (unlikely(running))
put_prev_task(rq, tsk);
- tg = container_of(task_css_check(tsk, cpu_cgrp_id,
- lockdep_is_held(&tsk->sighand->siglock)),
+ /*
+ * All callers are synchronized by task_rq_lock(); we do not use RCU
+ * which is pointless here. Thus, we pass "true" to task_css_check()
+ * to prevent lockdep warnings.
+ */
+ tg = container_of(task_css_check(tsk, cpu_cgrp_id, true),
struct task_group, css);
tg = autogroup_task_group(tsk, tg);
tsk->sched_task_group = tg;