Messages in this thread |  | | | Date | Tue, 28 Apr 2009 13:08:47 -0700 | | From | Andrew Morton <> | | Subject | Re: [PATCH -V2 01/13] mutex: add atomic_dec_and_mutex_lock |
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On Tue, 7 Apr 2009 16:06:01 -0700 Andrew Morton <akpm@linux-foundation.org> wrote:
> 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?
It still looks too large to be inlined.
Take a look at atomic_add_unless(), and split your sides laughing.
Once you factor in all the lockdep and other debug goop, the code generation here is pretty bewildering, but it won't be small.
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