freezer_cg: fix improper BUG_ON() causing oops
The BUG_ON() should be protected by freezer->lock, otherwise it can be triggered easily when a task has been unfreezed but the corresponding cgroup hasn't been changed to FROZEN state. Signed-off-by: Li Zefan <lizf@cn.fujitsu.com> Acked-by: Cedric Le Goater <clg@fr.ibm.com> Acked-by: Matt Helsley <matthltc@us.ibm.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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@ -190,8 +190,9 @@ static void freezer_fork(struct cgroup_subsys *ss, struct task_struct *task)
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freezer = task_freezer(task);
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task_unlock(task);
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BUG_ON(freezer->state == CGROUP_FROZEN);
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spin_lock_irq(&freezer->lock);
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BUG_ON(freezer->state == CGROUP_FROZEN);
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/* Locking avoids race with FREEZING -> THAWED transitions. */
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if (freezer->state == CGROUP_FREEZING)
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freeze_task(task, true);
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