linux-kernel - Re: [TIP/SCHED/DEVEL PATCH v3 4/6] sched: add sched_class->needs_post

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Message-ID: <alpine.DEB.1.10.0809041634580.3849@gandalf.stny.rr.com>
Date:	Thu, 4 Sep 2008 16:36:32 -0400 (EDT)
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Gregory Haskins <ghaskins@...ell.com>
cc:	mingo@...e.hu, peterz@...radead.org, linux-kernel@...r.kernel.org,
	linux-rt-users@...r.kernel.org, npiggin@...e.de,
	gregory.haskins@...il.com
Subject: Re: [TIP/SCHED/DEVEL PATCH v3 4/6] sched: add sched_class->needs_post_schedule()
 member



On Thu, 4 Sep 2008, Gregory Haskins wrote:
> diff --git a/kernel/sched.c b/kernel/sched.c
> index af4c6fa..ddc3877 100644
> --- a/kernel/sched.c
> +++ b/kernel/sched.c
> @@ -2525,6 +2525,14 @@ static void finish_task_switch(struct rq *rq, struct task_struct *prev)
>  {
>  	struct mm_struct *mm = rq->prev_mm;
>  	long prev_state;
> +#ifdef CONFIG_SMP
> +	int post_schedule = 0;
> +
> +	if (current->sched_class->needs_post_schedule) {
> +		BUG_ON(!current->sched_class->post_schedule);

The only one to ever hit this BUG_ON is a kernel developer creating a new
sched class. Since they should be smart enough to figure out why they get 
a segv later on, we really don't need it. Because this BUG_ON is also in 
a hot path, I strongly suggest nuking it.

-- Steve


> +		post_schedule = current->sched_class->needs_post_schedule(rq);
> +	}
> +#endif
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