Re: [PATCH] might_sleep() improvements

[Nick Piggin]

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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