Fix: consumerd: slow metadata push slows down application registration

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

diff --git a/src/common/waiter.cpp b/src/common/waiter.cpp
index b1e0adeccba00638a206c9e8171b6af44af6f201..d185e299720617e64e7514d114e33cea4a0eb386 100644 (file)
--- a/src/common/waiter.cpp
+++ b/src/common/waiter.cpp
@@ -7,6 +7,7 @@
  */
 
 #include "error.hpp"
+#include "macros.hpp"
 #include "waiter.hpp"
 
 #include <poll.h>
@@ -41,17 +42,21 @@ 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)) {
+               if (!futex_noasync(
+                           &waiter->state, FUTEX_WAIT, WAITER_WAITING, nullptr, nullptr, 0)) {
                        /*
                         * Prior queued wakeups queued by unrelated code
                         * using the same address can cause futex wait to
@@ -62,6 +67,7 @@ void lttng_waiter_wait(struct lttng_waiter *waiter)
                         */
                        continue;
                }
+
                switch (errno) {
                case EAGAIN:
                        /* Value already changed. */
@@ -88,13 +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);
+               poll(nullptr, 0, 10);
        }
+
        LTTNG_ASSERT(uatomic_read(&waiter->state) & WAITER_TEARDOWN);
-       DBG("End of waiter wait period");
+       DBG("End of waiter \"wait\" period");
 }
 
 /*
@@ -102,17 +111,49 @@ skip_futex_wait:
  * execution. In this scheme, the waiter owns the node memory, and we only allow
  * it to free this memory when it sees the WAITER_TEARDOWN flag.
  */
-void lttng_waiter_wake_up(struct lttng_waiter *waiter)
+void lttng_waiter_wake(struct lttng_waiter *waiter)
 {
        cmm_smp_mb();
        LTTNG_ASSERT(uatomic_read(&waiter->state) == WAITER_WAITING);
        uatomic_set(&waiter->state, WAITER_WOKEN_UP);
        if (!(uatomic_read(&waiter->state) & WAITER_RUNNING)) {
-               if (futex_noasync(&waiter->state, FUTEX_WAKE, 1, NULL, NULL, 0) < 0) {
+               if (futex_noasync(&waiter->state, FUTEX_WAKE, 1, nullptr, nullptr, 0) < 0) {
                        PERROR("futex_noasync");
                        abort();
                }
        }
+
        /* Allow teardown of struct urcu_wait memory. */
        uatomic_or(&waiter->state, WAITER_TEARDOWN);
 }
+
+void lttng_wait_queue_init(struct lttng_wait_queue *queue)
+{
+       cds_wfs_init(&queue->stack);
+}
+
+void lttng_wait_queue_add(struct lttng_wait_queue *queue, struct lttng_waiter *waiter)
+{
+       (void) cds_wfs_push(&queue->stack, &waiter->wait_queue_node);
+}
+
+void lttng_wait_queue_wake_all(struct lttng_wait_queue *queue)
+{
+       cds_wfs_head *waiters;
+       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) {
+               auto *waiter = lttng::utils::container_of(iter, &lttng_waiter::wait_queue_node);
+
+               /* Don't wake already running threads. */
+               if (waiter->state & WAITER_RUNNING) {
+                       continue;
+               }
+
+               lttng_waiter_wake(waiter);
+       }
+}