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?