50 lines
1.8 KiB
Diff
50 lines
1.8 KiB
Diff
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From: Kirill Tkhai <ktkhai@parallels.com>
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Date: Tue, 28 Oct 2014 08:24:34 +0300
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Subject: [PATCH] sched: Remove lockdep check in sched_move_task()
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sched_move_task() is the only interface to change sched_task_group:
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cpu_cgrp_subsys methods and autogroup_move_group() use it.
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Everything is synchronized by task_rq_lock(), so cpu_cgroup_attach()
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is ordered with other users of sched_move_task(). This means we do no
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need RCU here: if we've dereferenced a tg here, the .attach method
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hasn't been called for it yet.
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Thus, we should pass "true" to task_css_check() to silence lockdep
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warnings.
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Fixes: eeb61e53ea19 ("sched: Fix race between task_group and sched_task_group")
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Reported-by: Oleg Nesterov <oleg@redhat.com>
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Reported-by: Fengguang Wu <fengguang.wu@intel.com>
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Signed-off-by: Kirill Tkhai <ktkhai@parallels.com>
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Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
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Cc: Linus Torvalds <torvalds@linux-foundation.org>
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Link: http://lkml.kernel.org/r/1414473874.8574.2.camel@tkhai
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Signed-off-by: Ingo Molnar <mingo@kernel.org>
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---
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kernel/sched/core.c | 8 ++++++--
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1 file changed, 6 insertions(+), 2 deletions(-)
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diff --git a/kernel/sched/core.c b/kernel/sched/core.c
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index 240157c13ddc..6841fb46eb07 100644
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--- a/kernel/sched/core.c
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+++ b/kernel/sched/core.c
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@@ -7444,8 +7444,12 @@ void sched_move_task(struct task_struct *tsk)
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if (unlikely(running))
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put_prev_task(rq, tsk);
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- tg = container_of(task_css_check(tsk, cpu_cgrp_id,
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- lockdep_is_held(&tsk->sighand->siglock)),
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+ /*
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+ * All callers are synchronized by task_rq_lock(); we do not use RCU
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+ * which is pointless here. Thus, we pass "true" to task_css_check()
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+ * to prevent lockdep warnings.
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+ */
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+ tg = container_of(task_css_check(tsk, cpu_cgrp_id, true),
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struct task_group, css);
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tg = autogroup_task_group(tsk, tg);
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tsk->sched_task_group = tg;
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--
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1.9.3
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