On Fri, 2013-11-22 at 21:40 -0800, Darren Hart wrote: > On Fri, 2013-11-22 at 16:56 -0800, Davidlohr Bueso wrote: > > In futex_wake() there is clearly no point in taking the hb->lock if > > we know beforehand that there are no tasks to be woken. This comes > > at the smaller cost of doing some atomic operations to keep track of > > the list's size. Specifically, increment the counter when an element is > > added to the list, and decrement when it is removed. Of course, if the > > counter is 0, then there are no tasks blocked on a futex. Some special > > considerations: > > > > - increment the counter at queue_lock() as we always end up calling > > queue_me() which adds the element to the list. Upon any error, > > queue_unlock() is called for housekeeping, for which we decrement > > to mach the increment done in queue_lock(). > > > > - decrement the counter at __unqueue_me() to reflect when an element is > > removed from the queue for wakeup related purposes. > > What is the problem you are trying to solve here?
Apologies, too quick on the trigger. I see plenty of detail in 0/5. Will spend some time reviewing that. -- Darren Hart Intel Open Source Technology Center Yocto Project - Linux Kernel