On 10/13/2015 03:56 PM, Peter Zijlstra wrote:
On Tue, Sep 22, 2015 at 04:50:43PM -0400, Waiman Long wrote:+gotlock: /* + * We now have the lock. We need to either clear the tail code or + * notify the next one in queue as the new queue head. */ + old = atomic_read(&lock->val); + while ((old& _Q_TAIL_MASK) == tail) { + int val; + int new = old& ~_Q_TAIL_MASK; + + /* + * We are the only one in the queue, so clear the tail code + * and return. + */ + val = atomic_cmpxchg(&lock->val, old, new); + if (old == val) + goto done; + old = val; + } +This i need to think about a wee bit; its almost the same... So the below is exactly duplicated from the normal slowpath, so why don't you keep that there? It would get you something like: if (pv_wait_head_or_steal(..)) goto stolen; stolen:+ /* + * contended path; wait for next, release. + */ + while (!(next = READ_ONCE(node->next))) + cpu_relax(); + + arch_mcs_spin_unlock_contended(&next->locked); + pv_kick_node(lock, next);release: ...
Yes, it is largely the same. I thought that you don't like too much change in the logic flow of the generic qspinlock code. I will make the change in the next revision.
Cheers, Longman -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
