linux-kernel - Re: [PATCH 1/5] sched: Enable might_sleep before initializing drivers.

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Date:	Sat, 20 Nov 2010 11:42:35 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	John Stultz <john.stultz@...aro.org>
Cc:	lkml <linux-kernel@...r.kernel.org>,
	Arve Hjønnevåg <arve@...roid.com>,
	Ingo Molnar <mingo@...e.hu>
Subject: Re: [PATCH 1/5] sched: Enable might_sleep before initializing
 drivers.

On Fri, 2010-11-19 at 18:08 -0800, John Stultz wrote:
> From: Arve Hjønnevåg <arve@...roid.com>
> 
> This allows detection of init bugs in built-in drivers.
> 
> CC: Ingo Molnar <mingo@...e.hu>
> CC: Peter Zijlstra <peterz@...radead.org>
> Signed-off-by: Arve Hjønnevåg <arve@...roid.com>
> Signed-off-by: John Stultz <john.stultz@...aro.org>
> ---
>  kernel/sched.c |   13 ++++++++++++-
>  1 files changed, 12 insertions(+), 1 deletions(-)
> 
> diff --git a/kernel/sched.c b/kernel/sched.c
> index aa14a56..0b58415 100644
> --- a/kernel/sched.c
> +++ b/kernel/sched.c
> @@ -8104,13 +8104,24 @@ static inline int preempt_count_equals(int preempt_offset)
>  	return (nested == PREEMPT_INATOMIC_BASE + preempt_offset);
>  }
>  
> +static int __might_sleep_init_called;
> +int __init __might_sleep_init(void)
> +{
> +	__might_sleep_init_called = 1;
> +	return 0;
> +}
> +early_initcall(__might_sleep_init);
> +
>  void __might_sleep(const char *file, int line, int preempt_offset)
>  {
>  #ifdef in_atomic
>  	static unsigned long prev_jiffy;	/* ratelimiting */
>  
>  	if ((preempt_count_equals(preempt_offset) && !irqs_disabled()) ||
> -	    system_state != SYSTEM_RUNNING || oops_in_progress)
> +	    oops_in_progress)
> +		return;
> +	if (system_state != SYSTEM_RUNNING &&
> +	    (!__might_sleep_init_called || system_state != SYSTEM_BOOTING))
>  		return;
>  	if (time_before(jiffies, prev_jiffy + HZ) && prev_jiffy)
>  		return;

Remind me, why isn't scheduler_running good enough?
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