unix, windows: add thread barrier support

include/uv-private/uv-unix.h

@@ -108,6 +108,23 @@ typedef pthread_rwlock_t uv_rwlock_t;
 typedef UV_PLATFORM_SEM_T uv_sem_t;
 typedef pthread_cond_t uv_cond_t;
 
+
+#if defined(__APPLE__) && defined(__MACH__)
+
+typedef struct {
+  unsigned int n;
+  unsigned int count;
+  uv_mutex_t mutex;
+  uv_sem_t turnstile1;
+  uv_sem_t turnstile2;
+} uv_barrier_t;
+
+#else /* defined(__APPLE__) && defined(__MACH__) */
+
+typedef pthread_barrier_t uv_barrier_t;
+
+#endif /* defined(__APPLE__) && defined(__MACH__) */
+
 /* Platform-specific definitions for uv_spawn support. */
 typedef gid_t uv_gid_t;
 typedef uid_t uv_uid_t;

include/uv-private/uv-win.h

@@ -240,6 +240,14 @@ typedef union {
   } fallback_;
 } uv_rwlock_t;
 
+typedef struct {
+  unsigned int n;
+  unsigned int count;
+  uv_mutex_t mutex;
+  uv_sem_t turnstile1;
+  uv_sem_t turnstile2;
+} uv_barrier_t;
+
 #define UV_ONCE_INIT { 0, NULL }
 
 typedef struct uv_once_s {

include/uv.h

@@ -1821,6 +1821,10 @@ UV_EXTERN void uv_cond_wait(uv_cond_t* cond, uv_mutex_t* mutex);
 UV_EXTERN int uv_cond_timedwait(uv_cond_t* cond, uv_mutex_t* mutex,
     uint64_t timeout);
 
+UV_EXTERN int uv_barrier_init(uv_barrier_t* barrier, unsigned int count);
+UV_EXTERN void uv_barrier_destroy(uv_barrier_t* barrier);
+UV_EXTERN void uv_barrier_wait(uv_barrier_t* barrier);
+
 /* Runs a function once and only once. Concurrent calls to uv_once() with the
  * same guard will block all callers except one (it's unspecified which one).
  * The guard should be initialized statically with the UV_ONCE_INIT macro.

src/unix/thread.c

@@ -370,3 +370,83 @@ int uv_cond_timedwait(uv_cond_t* cond, uv_mutex_t* mutex, uint64_t timeout) {
 }
 
 #endif /* defined(__APPLE__) && defined(__MACH__) */
+
+
+#if defined(__APPLE__) && defined(__MACH__)
+
+int uv_barrier_init(uv_barrier_t* barrier, unsigned int count) {
+  barrier->n = count;
+  barrier->count = 0;
+
+  if (uv_mutex_init(&barrier->mutex))
+    return -1;
+
+  if (uv_sem_init(&barrier->turnstile1, 0))
+    goto error2;
+
+  if (uv_sem_init(&barrier->turnstile2, 1))
+    goto error;
+
+  return 0;
+
+error:
+  uv_sem_destroy(&barrier->turnstile1);
+error2:
+  uv_mutex_destroy(&barrier->mutex);
+  return -1;
+
+}
+
+
+void uv_barrier_destroy(uv_barrier_t* barrier) {
+  uv_sem_destroy(&barrier->turnstile2);
+  uv_sem_destroy(&barrier->turnstile1);
+  uv_mutex_destroy(&barrier->mutex);
+}
+
+
+void uv_barrier_wait(uv_barrier_t* barrier) {
+  uv_mutex_lock(&barrier->mutex);
+  if (++barrier->count == barrier->n) {
+    uv_sem_wait(&barrier->turnstile2);
+    uv_sem_post(&barrier->turnstile1);
+  }
+  uv_mutex_unlock(&barrier->mutex);
+
+  uv_sem_wait(&barrier->turnstile1);
+  uv_sem_post(&barrier->turnstile1);
+
+  uv_mutex_lock(&barrier->mutex);
+  if (--barrier->count == 0) {
+    uv_sem_wait(&barrier->turnstile1);
+    uv_sem_post(&barrier->turnstile2);
+  }
+  uv_mutex_unlock(&barrier->mutex);
+
+  uv_sem_wait(&barrier->turnstile2);
+  uv_sem_post(&barrier->turnstile2);
+}
+
+#else /* !(defined(__APPLE__) && defined(__MACH__)) */
+
+int uv_barrier_init(uv_barrier_t* barrier, unsigned int count) {
+  if (pthread_barrier_init(barrier, NULL, count))
+    return -1;
+  else
+    return 0;
+}
+
+
+void uv_barrier_destroy(uv_barrier_t* barrier) {
+  if (pthread_barrier_destroy(barrier))
+    abort();
+}
+
+
+void uv_barrier_wait(uv_barrier_t* barrier) {
+  int r = pthread_barrier_wait(barrier);
+  if (r && r != PTHREAD_BARRIER_SERIAL_THREAD)
+    abort();
+}
+
+#endif /* defined(__APPLE__) && defined(__MACH__) */

src/win/thread.c

@@ -610,3 +610,57 @@ int uv_cond_timedwait(uv_cond_t* cond, uv_mutex_t* mutex,
   else
     return uv_cond_fallback_timedwait(cond, mutex, timeout);
 }
+
+
+int uv_barrier_init(uv_barrier_t* barrier, unsigned int count) {
+  barrier->n = count;
+  barrier->count = 0;
+
+  if (uv_mutex_init(&barrier->mutex))
+    return -1;
+
+  if (uv_sem_init(&barrier->turnstile1, 0))
+    goto error2;
+
+  if (uv_sem_init(&barrier->turnstile2, 1))
+    goto error;
+
+  return 0;
+
+error:
+  uv_sem_destroy(&barrier->turnstile1);
+error2:
+  uv_mutex_destroy(&barrier->mutex);
+  return -1;
+
+}
+
+
+void uv_barrier_destroy(uv_barrier_t* barrier) {
+  uv_sem_destroy(&barrier->turnstile2);
+  uv_sem_destroy(&barrier->turnstile1);
+  uv_mutex_destroy(&barrier->mutex);
+}
+
+
+void uv_barrier_wait(uv_barrier_t* barrier) {
+  uv_mutex_lock(&barrier->mutex);
+  if (++barrier->count == barrier->n) {
+    uv_sem_wait(&barrier->turnstile2);
+    uv_sem_post(&barrier->turnstile1);
+  }
+  uv_mutex_unlock(&barrier->mutex);
+
+  uv_sem_wait(&barrier->turnstile1);
+  uv_sem_post(&barrier->turnstile1);
+
+  uv_mutex_lock(&barrier->mutex);
+  if (--barrier->count == 0) {
+    uv_sem_wait(&barrier->turnstile1);
+    uv_sem_post(&barrier->turnstile2);
+  }
+  uv_mutex_unlock(&barrier->mutex);
+
+  uv_sem_wait(&barrier->turnstile2);
+  uv_sem_post(&barrier->turnstile2);
+}

test/test-barrier.c

@@ -0,0 +1,98 @@
+/* Copyright Joyent, Inc. and other Node contributors. All rights reserved.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to
+ * deal in the Software without restriction, including without limitation the
+ * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
+ * sell copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
+ * IN THE SOFTWARE.
+ */
+
+#include "uv.h"
+#include "task.h"
+
+#include <string.h>
+#include <errno.h>
+
+typedef struct {
+  uv_barrier_t barrier;
+  int delay;
+  volatile int posted;
+} worker_config;
+
+
+static void worker(void* arg) {
+  worker_config* c = arg;
+
+  if (c->delay)
+    uv_sleep(c->delay);
+
+  uv_barrier_wait(&c->barrier);
+}
+
+
+TEST_IMPL(barrier_1) {
+  uv_thread_t thread;
+  worker_config wc;
+
+  memset(&wc, 0, sizeof(wc));
+
+  ASSERT(0 == uv_barrier_init(&wc.barrier, 2));
+  ASSERT(0 == uv_thread_create(&thread, worker, &wc));
+
+  uv_sleep(100);
+  uv_barrier_wait(&wc.barrier);
+
+  ASSERT(0 == uv_thread_join(&thread));
+  uv_barrier_destroy(&wc.barrier);
+
+  return 0;
+}
+
+
+TEST_IMPL(barrier_2) {
+  uv_thread_t thread;
+  worker_config wc;
+
+  memset(&wc, 0, sizeof(wc));
+  wc.delay = 100;
+
+  ASSERT(0 == uv_barrier_init(&wc.barrier, 2));
+  ASSERT(0 == uv_thread_create(&thread, worker, &wc));
+
+  uv_barrier_wait(&wc.barrier);
+
+  ASSERT(0 == uv_thread_join(&thread));
+  uv_barrier_destroy(&wc.barrier);
+
+  return 0;
+}
+
+
+TEST_IMPL(barrier_3) {
+  uv_thread_t thread;
+  worker_config wc;
+
+  memset(&wc, 0, sizeof(wc));
+
+  ASSERT(0 == uv_barrier_init(&wc.barrier, 2));
+  ASSERT(0 == uv_thread_create(&thread, worker, &wc));
+
+  uv_barrier_wait(&wc.barrier);
+
+  ASSERT(0 == uv_thread_join(&thread));
+  uv_barrier_destroy(&wc.barrier);
+
+  return 0;
+}

test/test-list.h

@@ -22,6 +22,9 @@
 TEST_DECLARE   (platform_output)
 TEST_DECLARE   (callback_order)
 TEST_DECLARE   (run_once)
+TEST_DECLARE   (barrier_1)
+TEST_DECLARE   (barrier_2)
+TEST_DECLARE   (barrier_3)
 TEST_DECLARE   (condvar_1)
 TEST_DECLARE   (condvar_2)
 TEST_DECLARE   (condvar_3)
@@ -214,6 +217,9 @@ TASK_LIST_START
   TEST_ENTRY  (callback_order)
 #endif
   TEST_ENTRY  (run_once)
+  TEST_ENTRY  (barrier_1)
+  TEST_ENTRY  (barrier_2)
+  TEST_ENTRY  (barrier_3)
   TEST_ENTRY  (condvar_1)
   TEST_ENTRY  (condvar_2)
   TEST_ENTRY  (condvar_3)

uv.gyp

@@ -305,6 +305,7 @@
         'test/test-mutexes.c',
         'test/test-signal.c',
         'test/test-thread.c',
+        'test/test-barrier.c',
         'test/test-condvar.c',
         'test/test-condvar-consumer-producer.c',
         'test/test-timer-again.c',