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SubjectRe: [PATCH 1/4] freezer_cg: fix improper BUG_ON() causing oops
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On Tue, 2008-10-21 at 08:48 +0800, Li Zefan wrote:
> 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: Matt Helsley <matthltc@us.ibm.com>

> ---
> kernel/cgroup_freezer.c | 3 ++-
> 1 files changed, 2 insertions(+), 1 deletions(-)
>
> diff --git a/kernel/cgroup_freezer.c b/kernel/cgroup_freezer.c
> index e950569..7f54d1c 100644
> --- a/kernel/cgroup_freezer.c
> +++ b/kernel/cgroup_freezer.c
> @@ -190,8 +190,9 @@ static void freezer_fork(struct cgroup_subsys *ss, struct task_struct *task)
> freezer = task_freezer(task);
> task_unlock(task);
>
> - BUG_ON(freezer->state == CGROUP_FROZEN);
> spin_lock_irq(&freezer->lock);
> + BUG_ON(freezer->state == CGROUP_FROZEN);
> +
> /* Locking avoids race with FREEZING -> THAWED transitions. */
> if (freezer->state == CGROUP_FREEZING)
> freeze_task(task, true);



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