Fix: consumerd: slow metadata push slows down application registration

[lttng-tools.git] / src / common / waiter.c

diff --git a/src/common/waiter.c b/src/common/waiter.c
index db2de6557f5df5a5465d66c8e2df591202953983..e72f53bd46ec31ab7582bda10bcd04ceeaf7f86f 100644 (file)
--- a/src/common/waiter.c
+++ b/src/common/waiter.c
@@ -43,15 +43,18 @@ void lttng_waiter_wait(struct lttng_waiter *waiter)
 {
        unsigned int i;
 
-       DBG("Beginning of waiter wait period");
-       /* Load and test condition before read state */
+       DBG("Beginning of waiter \"wait\" period");
+
+       /* Load and test condition before read state. */
        cmm_smp_rmb();
        for (i = 0; i < WAIT_ATTEMPTS; i++) {
                if (uatomic_read(&waiter->state) != WAITER_WAITING) {
                        goto skip_futex_wait;
                }
+
                caa_cpu_relax();
        }
+
        while (uatomic_read(&waiter->state) == WAITER_WAITING) {
                if (!futex_noasync(&waiter->state, FUTEX_WAIT, WAITER_WAITING, NULL, NULL, 0)) {
                        /*
@@ -64,6 +67,7 @@ void lttng_waiter_wait(struct lttng_waiter *waiter)
                         */
                        continue;
                }
+
                switch (errno) {
                case EAGAIN:
                        /* Value already changed. */
@@ -90,13 +94,16 @@ skip_futex_wait:
                if (uatomic_read(&waiter->state) & WAITER_TEARDOWN) {
                        break;
                }
+
                caa_cpu_relax();
        }
+
        while (!(uatomic_read(&waiter->state) & WAITER_TEARDOWN)) {
                poll(NULL, 0, 10);
        }
+
        assert(uatomic_read(&waiter->state) & WAITER_TEARDOWN);
-       DBG("End of waiter wait period");
+       DBG("End of waiter \"wait\" period");
 }
 
 /*
@@ -105,7 +112,7 @@ skip_futex_wait:
  * it to free this memory when it sees the WAITER_TEARDOWN flag.
  */
 LTTNG_HIDDEN
-void lttng_waiter_wake_up(struct lttng_waiter *waiter)
+void lttng_waiter_wake(struct lttng_waiter *waiter)
 {
        cmm_smp_mb();
        assert(uatomic_read(&waiter->state) == WAITER_WAITING);
@@ -117,6 +124,44 @@ void lttng_waiter_wake_up(struct lttng_waiter *waiter)
                        abort();
                }
        }
+
        /* Allow teardown of struct urcu_wait memory. */
        uatomic_or(&waiter->state, WAITER_TEARDOWN);
 }
+
+
+LTTNG_HIDDEN
+void lttng_wait_queue_init(struct lttng_wait_queue *queue)
+{
+       cds_wfs_init(&queue->stack);
+}
+
+LTTNG_HIDDEN
+void lttng_wait_queue_add(struct lttng_wait_queue *queue,
+               struct lttng_waiter *waiter)
+{
+       (void) cds_wfs_push(&queue->stack, &waiter->wait_queue_node);
+}
+
+LTTNG_HIDDEN
+void lttng_wait_queue_wake_all(struct lttng_wait_queue *queue)
+{
+       struct cds_wfs_head *waiters;
+       struct cds_wfs_node *iter, *iter_n;
+
+       /* Move all waiters from the queue to our local stack. */
+       waiters = __cds_wfs_pop_all(&queue->stack);
+
+       /* Wake all waiters in our stack head. */
+       cds_wfs_for_each_blocking_safe(waiters, iter, iter_n) {
+               struct lttng_waiter *waiter =
+                       container_of(iter, struct lttng_waiter, wait_queue_node);
+
+               /* Don't wake already running threads. */
+               if (waiter->state & WAITER_RUNNING) {
+                       continue;
+               }
+
+               lttng_waiter_wake(waiter);
+       }
+}