Buffered I/O: optimize lock taking in the common non-contended case.

diff --git a/Modules/_io/bufferedio.c b/Modules/_io/bufferedio.c
index 040f3bf9e76d0e272a80815d86d8da01bc68ec8c..9aa7d4b8b8c40c4270bec4644431a8cc5a8a3a86 100644 (file)
--- a/Modules/_io/bufferedio.c
+++ b/Modules/_io/bufferedio.c
@@ -260,9 +260,11 @@ typedef struct {
 
 #ifdef WITH_THREAD
 #define ENTER_BUFFERED(self) \
-    Py_BEGIN_ALLOW_THREADS \
-    PyThread_acquire_lock(self->lock, 1); \
-    Py_END_ALLOW_THREADS
+    if (!PyThread_acquire_lock(self->lock, 0)) { \
+        Py_BEGIN_ALLOW_THREADS \
+        PyThread_acquire_lock(self->lock, 1); \
+        Py_END_ALLOW_THREADS \
+    }
 
 #define LEAVE_BUFFERED(self) \
     PyThread_release_lock(self->lock);