deps: update libuv to 1.4.1

PR-URL: https://github.com/iojs/io.js/pull/940
Reviewed-By: Fedor Indutny <fedor@indutny.com>
Reviewed-By: Rod Vagg <rod@vagg.org>

1 files changed, 7 insertions, 35 deletions

diff --git a/deps/uv/src/unix/async.c b/deps/uv/src/unix/async.c
index b794ea6121..9ff24aeb3d 100644
--- a/deps/uv/src/unix/async.c
+++ b/deps/uv/src/unix/async.c
@@ -24,6 +24,7 @@
 
 #include "uv.h"
 #include "internal.h"
+#include "atomic-ops.h"
 
 #include <errno.h>
 #include <stdio.h>  /* snprintf() */
@@ -35,7 +36,6 @@
 static void uv__async_event(uv_loop_t* loop,
                             struct uv__async* w,
                             unsigned int nevents);
-static int uv__async_make_pending(int* pending);
 static int uv__async_eventfd(void);
 
 
@@ -58,7 +58,11 @@ int uv_async_init(uv_loop_t* loop, uv_async_t* handle, uv_async_cb async_cb) {
 
 
 int uv_async_send(uv_async_t* handle) {
-  if (uv__async_make_pending(&handle->pending) == 0)
+  /* Do a cheap read first. */
+  if (ACCESS_ONCE(int, handle->pending) != 0)
+    return 0;
+
+  if (cmpxchgi(&handle->pending, 0, 1) == 0)
     uv__async_send(&handle->loop->async_watcher);
 
   return 0;
@@ -80,9 +84,8 @@ static void uv__async_event(uv_loop_t* loop,
   QUEUE_FOREACH(q, &loop->async_handles) {
     h = QUEUE_DATA(q, uv_async_t, queue);
 
-    if (h->pending == 0)
+    if (cmpxchgi(&h->pending, 1, 0) == 0)
       continue;
-    h->pending = 0;
 
     if (h->async_cb == NULL)
       continue;
@@ -91,37 +94,6 @@ static void uv__async_event(uv_loop_t* loop,
 }
 
 
-static int uv__async_make_pending(int* pending) {
-  /* Do a cheap read first. */
-  if (ACCESS_ONCE(int, *pending) != 0)
-    return 1;
-
-  /* Micro-optimization: use atomic memory operations to detect if we've been
-   * preempted by another thread and don't have to make an expensive syscall.
-   * This speeds up the heavily contended case by about 1-2% and has little
-   * if any impact on the non-contended case.
-   *
-   * Use XCHG instead of the CMPXCHG that __sync_val_compare_and_swap() emits
-   * on x86, it's about 4x faster. It probably makes zero difference in the
-   * grand scheme of things but I'm OCD enough not to let this one pass.
-   */
-#if defined(__i386__) || defined(__x86_64__)
-  {
-    unsigned int val = 1;
-    __asm__ __volatile__ ("xchgl %0, %1"
-                         : "+r" (val)
-                         : "m"  (*pending));
-    return val != 0;
-  }
-#elif defined(__GNUC__) && (__GNUC__ > 4 || __GNUC__ == 4 && __GNUC_MINOR__ > 0)
-  return __sync_val_compare_and_swap(pending, 0, 1) != 0;
-#else
-  ACCESS_ONCE(int, *pending) = 1;
-  return 0;
-#endif
-}
-
-
 static void uv__async_io(uv_loop_t* loop, uv__io_t* w, unsigned int events) {
   struct uv__async* wa;
   char buf[1024];