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From: Daniel Phillips <phillips@arcor.de>
To: Arnd Bergmann <arnd@bergmann-dalldorf.de>, linux-kernel@vger.kernel.org
Subject: Re: spinlock assertion macros
Date: Fri, 12 Jul 2002 19:42:09 +0200
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Cc: Jesse Barnes <jbarnes@sgi.com>,
       kernel-janitor-discuss@lists.sourceforge.net
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On Friday 12 July 2002 21:24, Arnd Bergmann wrote:
> Daniel Phillips wrote:
> 
> > Any idea how one might implement NEVER_SLEEPS()?  Maybe as:
> 
> Why would you want that? AFAICS there are two kinds of "never
> sleeping" functions: 1. those that don't sleep but don't care
> about it and 2. those that must not sleep because a lock is
> held.
> 
> For 1. no point marking it because it might change without
> being a bug. You also don't want to mark every function
> in the kernel SLEEPS() or NEVER_SLEEPS().
> 
> For 2. we already have MUST_HOLD(foo) or similar, which implicitly 
> means it can never sleep. The same is true for functions
> with spinlocks or preempt_disable around their body.

Thanks for that.

So far, only the MUST_HOLD style of executable locking documentation has 
really survived scrutiny.  It needs some variants: MUST_HOLD_READ, 
MUST_HOLD_WRITE, MUST_HOLD_SEM, MUST_HOLD_READ_SEM and MUST_HOLD_WRITE_SEM, 
or names to that effect.

-- 
Daniel
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