Messages in this thread | | | Date | Thu, 25 Aug 2016 10:11:41 +0200 | From | Peter Zijlstra <> | Subject | Re: [RFC][PATCH 3/3] locking/mutex: Add lock handoff to avoid starvation |
| |
On Wed, Aug 24, 2016 at 03:50:10PM -0400, Waiman Long wrote:
> --- a/kernel/locking/mutex.c > +++ b/kernel/locking/mutex.c > @@ -97,6 +97,8 @@ static void __mutex_handoff(struct mutex *lock, struct > task_st > for (;;) { > unsigned long old, new; > > + if ((owner & ~MUTEX_FLAG_ALL) != current) > + break; > new = (owner & MUTEX_FLAG_WAITERS); > new |= (unsigned long)task; > > I also think that the MUTEX_FLAG_HANDOFF bit needs to be cleared if the list > is empty. > > @@ -614,7 +633,7 @@ __mutex_lock_common(struct mutex *lock, long state, > unsigned > mutex_remove_waiter(lock, &waiter, task); > /* set it to 0 if there are no waiters left: */ > if (likely(list_empty(&lock->wait_list))) > - __mutex_clear_flag(lock, MUTEX_FLAG_WAITERS); > + __mutex_clear_flag(lock, > MUTEX_FLAG_WAITERS|MUTEX_FLAG_HANDOFF); > > Or we should try to reset the handoff bit after the while loop exit if the > bit is still set.
Yes, I think you're right. I've also found another issue wrt WAITERS in patch 1.
I'm not trying to get aim7 running to see if I can reproduce Jason's results and verify things.
| |