On Wed, Jan 15, 2014 at 10:46:17PM -0800, Jason Low wrote: > On Thu, 2014-01-16 at 10:14 +0700, Linus Torvalds wrote: > > On Thu, Jan 16, 2014 at 9:45 AM, Jason Low <jason.l...@hp.com> wrote: > > > > > > Any comments on the below change which unlocks the mutex before taking > > > the lock->wait_lock to wake up a waiter? Thanks. > > > > Hmm. Doesn't that mean that a new lock owner can come in *before* > > you've called debug_mutex_unlock and the lockdep stuff, and get the > > lock? And then debug_mutex_lock() will be called *before* the unlocker > > called debug_mutex_unlock(), which I'm sure confuses things. > > If obtaining the wait_lock for debug_mutex_unlock is the issue, then > perhaps we can address that by taking care of > #ifdef CONFIG_DEBUG_MUTEXES. In the CONFIG_DEBUG_MUTEXES case, we can > take the wait_lock first, and in the regular case, take the wait_lock > after releasing the mutex.
I think we're already good for DEBUG_MUTEXES, because DEBUG_MUTEXES has to work for archs that have !__mutex_slowpath_needs_to_unlock() and also the DEBUG_MUTEXES code is entirely serialized on ->wait_lock. Note that we cannot do the optimistic spinning for DEBUG_MUTEXES exactly because of this reason. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
