linux-kernel - Re: [RFC] "mustnotsleep"

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Message-ID: <87hb87lsb0.fsf@gmail.com>
Date:	Fri, 03 Jun 2011 00:36:19 +0100
From:	Luis Henriques <luis.henrix@...il.com>
To:	Dan Magenheimer <dan.magenheimer@...cle.com>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: [RFC] "mustnotsleep"

Dan Magenheimer <dan.magenheimer@...cle.com> writes:

> In development of RAMster, I have frequently been bitten
> by indirect use of existing kernel subsystems that
> unexpectedly sleep.  As such, I have hacked the
> following "debug" code fragments for use where I need to
> ensure that doesn't happen.
>
> DEFINE_PER_CPU(int, mustnotsleep_count);
>
> void mustnotsleep_start(void)
> {
> 	int cpu = smp_processor_id();
> 	per_cpu(mustnotsleep_count, cpu)++;
> }
>
> void mustnotsleep_done(void)
> {
> 	int cpu = smp_processor_id();
> 	per_cpu(mustnotsleep_count, cpu)--;
> }
>
> and in schedule.c in schedule():
>
> if (per_cpu(mustnotsleep_count))
> 	panic("scheduler called in mustnotsleep code");
>
> This has enabled me to start identifying code that
> is causing me problems.  (I know this is a horrible
> hack, but that's OK right now.)

I'm pretty sure I'm missing something here but... what if you just use
CONFIG_DEBUG_PREEMPT?  Isn't that good enough?

Cheers,
--
Luis Henriques
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