On 04/18/2014 03:46 AM, Ingo Molnar wrote:
* Waiman Long<waiman.long@xxxxxx> wrote:
On 04/17/2014 11:58 AM, Peter Zijlstra wrote:
On Thu, Apr 17, 2014 at 11:03:57AM -0400, Waiman Long wrote:
+static __always_inline void
+clear_pending_set_locked(struct qspinlock *lock, u32 val)
+{
+ struct __qspinlock *l = (void *)lock;
+
+ ACCESS_ONCE(l->locked_pending) = 1;
+}
@@ -157,8 +251,13 @@ static inline int trylock_pending(struct qspinlock *lock, u32 *pval)
* we're pending, wait for the owner to go away.
*
* *,1,1 -> *,1,0
+ *
+ * this wait loop must be a load-acquire such that we match the
+ * store-release that clears the locked bit and create lock
+ * sequentiality; this because not all try_clear_pending_set_locked()
+ * implementations imply full barriers.
You renamed the function referred in the above comment.
Sorry, will fix the comments.
I suggest not renaming the function instead.
try_clear_pending_set_locked() tells the intent in a clearer fashion.
Thanks,
Ingo
I usually use the word "try" if there is a possibility of failure.
However, the function will always succeed, albeit by waiting a bit in
some cases. That is why I remove "try" from the name.
-Longman
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