Messages in this thread | | | Date | Fri, 6 Nov 2015 21:37:09 +0100 | From | Peter Zijlstra <> | Subject | Re: [PATCH tip/locking/core v9 6/6] locking/pvqspinlock: Queue node adaptive spinning |
| |
On Fri, Nov 06, 2015 at 12:54:06PM -0500, Waiman Long wrote: > >>+static void pv_wait_node(struct mcs_spinlock *node, struct mcs_spinlock *prev) > >> { > >> struct pv_node *pn = (struct pv_node *)node; > >>+ struct pv_node *pp = (struct pv_node *)prev; > >> int waitcnt = 0; > >> int loop; > >>+ bool wait_early; > >> > >> /* waitcnt processing will be compiled out if !QUEUED_LOCK_STAT */ > >> for (;; waitcnt++) { > >>- for (loop = SPIN_THRESHOLD; loop; loop--) { > >>+ for (wait_early = false, loop = SPIN_THRESHOLD; loop; loop--) { > >> if (READ_ONCE(node->locked)) > >> return; > >>+ if (pv_wait_early(pp, loop)) { > >>+ wait_early = true; > >>+ break; > >>+ } > >> cpu_relax(); > >> } > >> > >So if prev points to another node, it will never see vcpu_running. Was > >that fully intended? > > I had added code in pv_wait_head_or_lock to set the state appropriately for > the queue head vCPU.
Yes, but that's the head, for nodes we'll always have halted or hashed.
| |