On Wed, May 22, 2013 at 07:24:38PM +0200, Maarten Lankhorst wrote: > >> +static inline void ww_acquire_init(struct ww_acquire_ctx *ctx, > >> + struct ww_class *ww_class) > >> +{ > >> + ctx->task = current; > >> + do { > >> + ctx->stamp = atomic_long_inc_return(&ww_class->stamp); > >> + } while (unlikely(!ctx->stamp)); > > I suppose we'll figure something out when this becomes a bottleneck. Ideally > > we'd do something like: > > > > ctx->stamp = local_clock(); > > > > but for now we cannot guarantee that's not jiffies, and I suppose that's a > > tad > > too coarse to work for this. > This might mess up when 2 cores happen to return exactly the same time, how > do you choose a winner in that case? > EDIT: Using pointer address like you suggested below is fine with me. ctx > pointer would be static enough.
Right, but for now I suppose the 'global' atomic is ok, if/when we find it hurts performance we can revisit. I was just spewing ideas :-) > > Also, why is 0 special? > Oops, 0 is no longer special. > > I used to set the samp directly on the lock, so 0 used to mean no ctx set. Ah, ok :-) > >> +static inline int __must_check ww_mutex_trylock_single(struct ww_mutex > >> *lock) > >> +{ > >> + return mutex_trylock(&lock->base); > >> +} > > trylocks can never deadlock they don't block per definition, I don't see the > > point of the _single() thing here. > I called it single because they weren't annotated into any ctx. I can drop > the _single suffix though, > but you'd still need to unlock with unlock_single, or we need to remove that > distinction altogether, > lose a few lockdep checks and only have a one unlock function. Again, early.. monday.. would a trylock, even if successful still need the ctx? -- 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/