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    SubjectRe: 2.4.2-ac3: loop threads in D state


    On Sun, 25 Feb 2001, Alexander Viro wrote:

    >
    >
    > 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.

    Let me elaborate: the race is very narrow and takes deliberate efforts to
    hit. It _can_ be triggered, unfortunately. This extra up() will mess your
    life later on.

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