Initial checkin of gRPC to third_party/

third_party/grpc/src/core/support/sync.c

+/*
+ *
+ * Copyright 2015-2016, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+/* Generic implementation of synchronization primitives. */
+
+#include <grpc/support/log.h>
+#include <grpc/support/sync.h>
+#include <grpc/support/atm.h>
+
+/* Number of mutexes to allocate for events, to avoid lock contention.
+   Should be a prime. */
+enum { event_sync_partitions = 31 };
+
+/* Events are partitioned by address to avoid lock contention. */
+static struct sync_array_s {
+  gpr_mu mu;
+  gpr_cv cv;
+} sync_array[event_sync_partitions];
+
+/* This routine is executed once on first use, via event_once */
+static gpr_once event_once = GPR_ONCE_INIT;
+static void event_initialize(void) {
+  int i;
+  for (i = 0; i != event_sync_partitions; i++) {
+    gpr_mu_init(&sync_array[i].mu);
+    gpr_cv_init(&sync_array[i].cv);
+  }
+}
+
+/* Hash ev into an element of sync_array[]. */
+static struct sync_array_s *hash(gpr_event *ev) {
+  return &sync_array[((uintptr_t)ev) % event_sync_partitions];
+}
+
+void gpr_event_init(gpr_event *ev) {
+  gpr_once_init(&event_once, &event_initialize);
+  ev->state = 0;
+}
+
+void gpr_event_set(gpr_event *ev, void *value) {
+  struct sync_array_s *s = hash(ev);
+  gpr_mu_lock(&s->mu);
+  GPR_ASSERT(gpr_atm_acq_load(&ev->state) == 0);
+  gpr_atm_rel_store(&ev->state, (gpr_atm)value);
+  gpr_cv_broadcast(&s->cv);
+  gpr_mu_unlock(&s->mu);
+  GPR_ASSERT(value != NULL);
+}
+
+void *gpr_event_get(gpr_event *ev) {
+  return (void *)gpr_atm_acq_load(&ev->state);
+}
+
+void *gpr_event_wait(gpr_event *ev, gpr_timespec abs_deadline) {
+  void *result = (void *)gpr_atm_acq_load(&ev->state);
+  if (result == NULL) {
+    struct sync_array_s *s = hash(ev);
+    gpr_mu_lock(&s->mu);
+    do {
+      result = (void *)gpr_atm_acq_load(&ev->state);
+    } while (result == NULL && !gpr_cv_wait(&s->cv, &s->mu, abs_deadline));
+    gpr_mu_unlock(&s->mu);
+  }
+  return result;
+}
+
+void gpr_ref_init(gpr_refcount *r, int n) { gpr_atm_rel_store(&r->count, n); }
+
+void gpr_ref(gpr_refcount *r) { gpr_atm_no_barrier_fetch_add(&r->count, 1); }
+
+void gpr_ref_non_zero(gpr_refcount *r) {
+  gpr_atm prior = gpr_atm_no_barrier_fetch_add(&r->count, 1);
+  GPR_ASSERT(prior > 0);
+}
+
+void gpr_refn(gpr_refcount *r, int n) {
+  gpr_atm_no_barrier_fetch_add(&r->count, n);
+}
+
+int gpr_unref(gpr_refcount *r) {
+  gpr_atm prior = gpr_atm_full_fetch_add(&r->count, -1);
+  GPR_ASSERT(prior > 0);
+  return prior == 1;
+}
+
+void gpr_stats_init(gpr_stats_counter *c, intptr_t n) {
+  gpr_atm_rel_store(&c->value, n);
+}
+
+void gpr_stats_inc(gpr_stats_counter *c, intptr_t inc) {
+  gpr_atm_no_barrier_fetch_add(&c->value, inc);
+}
+
+intptr_t gpr_stats_read(const gpr_stats_counter *c) {
+  /* don't need acquire-load, but we have no no-barrier load yet */
+  return gpr_atm_acq_load(&c->value);
+}