Re: [PATCH] scheduler: convert BUG_ON()s in try_to_wake_up_local() to WARN_ON_ONCE()s

Steven Rostedt
2013-03-18T19:32:24Z

On Mon, 2013-03-18 at 12:22 -0700, Tejun Heo wrote:
> try_to_wake_up_local() should only be invoked to wake up another task
> in the same runqueue and BUG_ON()s are used to enforce the rule.
> Missing try_to_wake_up_local() can stall workqueue execution but such
> stalls are likely to be finite either by another work item being
> queued or the one blocked getting unblocked. There's no reason to
> trigger BUG while holding rq lock crashing the whole system.
>
> Convert BUG_ON()s in try_to_wake_up_local() to WARN_ON_ONCE()s.
>
> Signed-off-by: Tejun Heo <tj@kernel.org>
> Cc: Steven Rostedt <rostedt@goodmis.org>

Acked-by: Steven Rostedt <rostedt@goodmis.org>

-- Steve

> ---
> kernel/sched/core.c | 6 ++++--
> 1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index 7f12624..a2eda4d 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -1498,8 +1498,10 @@ static void try_to_wake_up_local(struct task_struct *p)
> {
> struct rq *rq = task_rq(p);
>
> - BUG_ON(rq != this_rq());
> - BUG_ON(p == current);
> + if (WARN_ON_ONCE(rq != this_rq()) ||
> + WARN_ON_ONCE(p == current))
> + return;
> +
> lockdep_assert_held(&rq->lock);
>
> if (!raw_spin_trylock(&p->pi_lock)) {