linux-kernel - Re: [PATCH] sched/deadline: fix BUG_ON() ENQUEUE

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Date:   Mon, 8 Feb 2021 11:41:31 +0100
From:   Juri Lelli <juri.lelli@...hat.com>
To:     trix@...hat.com
Cc:     mingo@...hat.com, peterz@...radead.org, vincent.guittot@...aro.org,
        dietmar.eggemann@....com, rostedt@...dmis.org, bsegall@...gle.com,
        mgorman@...e.de, bristot@...hat.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] sched/deadline: fix BUG_ON() ENQUEUE_REPLENISH check

Hi,

On 06/02/21 12:48, trix@...hat.com wrote:
> From: Tom Rix <trix@...hat.com>
> 
> When the BUG_ON check for (flags != ENQUEUE_REPLENISH) was created, the
> flag was set to ENQUEUE_REPLENISH in rt_mutex_setprio(), now it is or-ed
> in.  So the checking logic needs to change.
> 
> Fixes: 1de64443d755 ("sched/core: Fix task and run queue sched_info::run_delay inconsistencies")
> Signed-off-by: Tom Rix <trix@...hat.com>
> ---
>  kernel/sched/deadline.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
> index 1508d126e88b..f50d20b7fe7c 100644
> --- a/kernel/sched/deadline.c
> +++ b/kernel/sched/deadline.c
> @@ -1561,7 +1561,7 @@ static void enqueue_task_dl(struct rq *rq, struct task_struct *p, int flags)
>  		 * the throttle.
>  		 */
>  		p->dl.dl_throttled = 0;
> -		BUG_ON(!is_dl_boosted(&p->dl) || flags != ENQUEUE_REPLENISH);
> +		BUG_ON(!is_dl_boosted(&p->dl) || !(flags & ENQUEUE_REPLENISH));

Uhu, isn't this actually the else branch of "if (is_dl_boosted())"? If
yes, I don't see how this is not always triggering. :-/

Thanks,
Juri