On Mon, May 27, 2013 at 12:52:00PM +0200, Maarten Lankhorst wrote: > The reason ttm needed it was because there was another lock that interacted > with the ctx lock in a weird way. The ww lock it was using was inverted with another > lock, so it had to grab that lock first, perform a trylock on the ww lock, and if that failed > unlock the lock, wait for it to be unlocked, then retry the same thing again. > I'm so glad I managed to fix that mess, if you really need ww_mutex_trylock with a ctx, > it's an indication your locking is wrong. > > For ww_mutex_trylock with a context to be of any use you would also need to return > 0 or a -errno, (-EDEADLK, -EBUSY (already locked by someone else), or -EALREADY). > This would make the trylock very different from other trylocks, and very confusing because > if (ww_mutex_trylock(lock, ctx)) would not do what you would think it would do. Yuck ;-) Anyway, what I was thinking of is something like: T0 T1 try A lock B lock B lock A Now, if for some reason T1 won the lottery such that T0 would have to be wounded, T0's context would indicate its the first entry and not return -EDEADLK. OTOH, anybody doing creative things like that might well deserve whatever they get ;-) > > The thing is; if there could exist something like: > > > > ww_mutex_trylock(struct ww_mutex *, struct ww_acquire_ctx *ctx); > > > > Then we should not now take away that name and make it mean something > > else; namely: ww_mutex_trylock_single(). > > > > Unless we want to allow .ctx=NULL to mean _single. > > > > As to why I proposed that (.ctx=NULL meaning _single); I suppose because > > I'm a minimalist at heart. > Minimalism isn't bad, it's just knowing when to sto :-) _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx http://lists.freedesktop.org/mailman/listinfo/dri-devel
