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    SubjectRe: [PATCH] Fix race between attach_task and cpuset_exit
    On Sun, Mar 25, 2007 at 11:22:15PM +0530, Balbir Singh wrote:
    > >+ struct cpuset *oldcs_tobe_released = NULL;
    >
    > How about oldcs_to_be_released?

    Yes, I wanted to use that, but my typo I guess.

    > >@@ -2242,19 +2241,20 @@ void cpuset_exit(struct task_struct *tsk
    > > {
    > > struct cpuset *cs;
    > >
    > >+ task_lock(tsk);
    > > cs = tsk->cpuset;
    > > tsk->cpuset = &top_cpuset; /* the_top_cpuset_hack - see above */
    > >+ atomic_dec(&cs->count);
    >
    > How about using a local variable like ref_count and using
    >
    > ref_count = atomic_dec_and_test(&cs->count); This will avoid the two
    > atomic operations, atomic_dec() and atomic_read() below.

    Well, someone may have attached to this cpuset while we were waiting on the
    mutex_lock(). So we need to do a atomic_read again to ensure it is still
    unused. But I notice that check_for_release() has that
    atomic_read-and-check-for-zero-refcount inbuilt into it, which means we can
    blindly call it. Modified patch in another mail.

    --
    Regards,
    vatsa
    -
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