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    SubjectRe: [PATCH -V2 01/13] mutex: add atomic_dec_and_mutex_lock
    On Fri, 27 Mar 2009 16:05:08 -0400
    Eric Paris <eparis@redhat.com> wrote:

    > Much like the atomic_dec_and_lock() function in which we take an hold a
    > spin_lock if we drop the atomic to 0 this function takes and holds the
    > mutex if we dec the atomic to 0.
    >
    > Signed-off-by: Eric Paris <eparis@redhat.com>
    > Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
    > Cc: Paul Mackerras <paulus@samba.org>
    > LKML-Reference: <20090323172417.410913479@chello.nl>
    > Signed-off-by: Ingo Molnar <mingo@elte.hu>
    > ---
    >
    > include/linux/mutex.h | 23 +++++++++++++++++++++++
    > 1 files changed, 23 insertions(+), 0 deletions(-)
    >
    > diff --git a/include/linux/mutex.h b/include/linux/mutex.h
    > index 3069ec7..93054fc 100644
    > --- a/include/linux/mutex.h
    > +++ b/include/linux/mutex.h
    > @@ -151,4 +151,27 @@ extern int __must_check mutex_lock_killable(struct mutex *lock);
    > extern int mutex_trylock(struct mutex *lock);
    > extern void mutex_unlock(struct mutex *lock);
    >
    > +/**
    > + * atomic_dec_and_mutex_lock - return holding mutex if we dec to 0
    > + * @cnt: the atomic which we are to dec
    > + * @lock: the mutex to return holding if we dec to 0
    > + *
    > + * return true and hold lock if we dec to 0, return false otherwise
    > + */
    > +static inline int atomic_dec_and_mutex_lock(atomic_t *cnt, struct mutex *lock)
    > +{
    > + /* dec if we can't possibly hit 0 */
    > + if (atomic_add_unless(cnt, -1, 1))
    > + return 0;
    > + /* we might hit 0, so take the lock */
    > + mutex_lock(lock);
    > + if (!atomic_dec_and_test(cnt)) {
    > + /* when we actually did the dec, we didn't hit 0 */
    > + mutex_unlock(lock);
    > + return 0;
    > + }
    > + /* we hit 0, and we hold the lock */
    > + return 1;
    > +}
    > +

    This looks too large to be inlined?


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