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| author | Kirill Tkhai <ktkhai@parallels.com> | 2014-10-28 08:24:34 +0300 |
|---|---|---|
| committer | Jiri Slaby <jslaby@suse.cz> | 2016-05-19 11:00:14 +0200 |
| commit | a1178cc54d48ba39b84bc61eccc30dc92a6b13f6 (patch) | |
| tree | 987592041aed7f3c050be27eed49d6590579802e | |
| parent | 012d81589afb85807b7ebe72f3505d90f34aa265 (diff) | |
| download | lwn-a1178cc54d48ba39b84bc61eccc30dc92a6b13f6.tar.gz lwn-a1178cc54d48ba39b84bc61eccc30dc92a6b13f6.zip | |
sched: Remove lockdep check in sched_move_task()
commit f7b8a47da17c9ee4998f2ca2018fcc424e953c0e upstream.
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>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
| -rw-r--r-- | kernel/sched/core.c | 8 |
1 files changed, 6 insertions, 2 deletions
diff --git a/kernel/sched/core.c b/kernel/sched/core.c index dd794a9b6850..e382c14652d0 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -6865,8 +6865,12 @@ void sched_move_task(struct task_struct *tsk) if (unlikely(running)) tsk->sched_class->put_prev_task(rq, tsk); - tg = container_of(task_css_check(tsk, cpu_cgroup_subsys_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_cgroup_subsys_id, true), struct task_group, css); tg = autogroup_task_group(tsk, tg); tsk->sched_task_group = tg; |