Re: 2.4.2-ac3: loop threads in D state

From: Alexander Viro (viro@math.psu.edu)
Date: Sun Feb 25 2001 - 19:36:11 EST


On Mon, 26 Feb 2001, Jens Axboe wrote:

> On Sun, Feb 25 2001, Alexander Viro wrote:
> > Erm... Jens, it really should be
> > if (atomic_dec_and_test(...))
> > up(...);
> > not just
> > atomic_dec(...);
> > up(...);
> >
> > Otherwise you can end up with too early exit of loop_thread. Normally
> > it would not matter, but in pathological cases...
>
> How so? We dec it and up the semaphore, loop_thread runs until it's
> done and ups lo_sem.

You are risking an extra up() here. Think what happens if you already had a
pending request.

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