Message-ID: <3F545883.8090800@cyberone.com.au>
Date: Tue, 02 Sep 2003 18:44:51 +1000
From: Nick Piggin <piggin@cyberone.com.au>
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To: torvalds@osdl.org
CC: linux-kernel@vger.kernel.org
Subject: Re: [PATCH] might_sleep() improvements
References: <20030902075145.GA12817@sfgoth.com> <3F545175.1080505@cyberone.com.au> <bj1kr3$a2g$1@build.pdx.osdl.net>
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Linus Torvalds wrote:

>Nick Piggin wrote:
>
>>I think these should be pushed down to where the sleeping
>>actually happens if possible.
>>
>
>No, that ends up doing the wrong thing for most of the really common cases.
>
>In particular, most of the memory allocation functions very seldom actually
>sleep. After all, they'll find plenty of free memory (or easily freeable
>memory) without having to wait for any pageouts or anything like that.
>
>Yet the bug is there - the call _could_ have slept.
>
>So "might_sleep()" really does what the name suggests: it is used to say
>that a particular case _may_ sleep, even if it ends up being unlikely.
>
>Because what we're after is not a bug actually happening, but a latent bug
>that has been hidden by the fact that it happens so rarely in practice.
>
>This is why "might_sleep()" should happen as early as possible, and not
>get pushed down.
>
>

Yes I see. I agree. I thought some could be pushed down further without
losing info. I was mainly worried about adding the might_sleep_if
function.


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