Re: [PATCH] shm: optimize exit_shm()

[Oleg Nesterov]

On 08/03, Vasiliy Kulikov wrote:
>
> On Wed, Aug 03, 2011 at 21:21 +0200, Oleg Nesterov wrote:
> > > we should check .in_use once again after
> > > down_write().
> >
> > Why?
>
> https://lkml.org/lkml/2011/8/3/277
>
> "No, as I said in the comment above, other task may be holding the mutex and
> deleting the last shm segment.

This is obvious,

> "Should" == additional check might speed the things, so it worth checking.

and this is not.

I was confused, the changelog looks as if we _have to_ recheck
or something bad can happen.

But as I said, the patch looks correct anyway. I am not
sure the 2nd optimization really makes sense (this is very
unlikely case) but it doesn't hurt.

Oleg.

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