From 234f07f16cc845128658cc0b39ac681cae5a8fba Mon Sep 17 00:00:00 2001
From: Damien George <damien.p.george@gmail.com>
Date: Mon, 6 Feb 2017 10:47:20 +1100
Subject: [PATCH] py/modthread: Use system-provided mutexs for _thread locks.

It's more efficient using the system mutexs instead of synthetic ones with
a busy-wait loop.  The system can do proper scheduling and blocking of the
threads waiting on the mutex.
---
 py/modthread.c | 25 ++++---------------------
 1 file changed, 4 insertions(+), 21 deletions(-)

diff --git a/py/modthread.c b/py/modthread.c
index 6f55281adc..975e7d1f63 100644
--- a/py/modthread.c
+++ b/py/modthread.c
@@ -44,24 +44,19 @@
 
 /****************************************************************/
 // Lock object
-// Note: with the GIL enabled we can easily synthesise a lock object
 
 STATIC const mp_obj_type_t mp_type_thread_lock;
 
 typedef struct _mp_obj_thread_lock_t {
     mp_obj_base_t base;
-    #if !MICROPY_PY_THREAD_GIL
     mp_thread_mutex_t mutex;
-    #endif
     volatile bool locked;
 } mp_obj_thread_lock_t;
 
 STATIC mp_obj_thread_lock_t *mp_obj_new_thread_lock(void) {
     mp_obj_thread_lock_t *self = m_new_obj(mp_obj_thread_lock_t);
     self->base.type = &mp_type_thread_lock;
-    #if !MICROPY_PY_THREAD_GIL
     mp_thread_mutex_init(&self->mutex);
-    #endif
     self->locked = false;
     return self;
 }
@@ -73,20 +68,9 @@ STATIC mp_obj_t thread_lock_acquire(size_t n_args, const mp_obj_t *args) {
         wait = mp_obj_get_int(args[1]);
         // TODO support timeout arg
     }
-    #if MICROPY_PY_THREAD_GIL
-    if (self->locked) {
-        if (!wait) {
-            return mp_const_false;
-        }
-        do {
-            MP_THREAD_GIL_EXIT();
-            MP_THREAD_GIL_ENTER();
-        } while (self->locked);
-    }
-    self->locked = true;
-    return mp_const_true;
-    #else
+    MP_THREAD_GIL_EXIT();
     int ret = mp_thread_mutex_lock(&self->mutex, wait);
+    MP_THREAD_GIL_ENTER();
     if (ret == 0) {
         return mp_const_false;
     } else if (ret == 1) {
@@ -95,7 +79,6 @@ STATIC mp_obj_t thread_lock_acquire(size_t n_args, const mp_obj_t *args) {
     } else {
         mp_raise_OSError(-ret);
     }
-    #endif
 }
 STATIC MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(thread_lock_acquire_obj, 1, 3, thread_lock_acquire);
 
@@ -103,9 +86,9 @@ STATIC mp_obj_t thread_lock_release(mp_obj_t self_in) {
     mp_obj_thread_lock_t *self = MP_OBJ_TO_PTR(self_in);
     // TODO check if already unlocked
     self->locked = false;
-    #if !MICROPY_PY_THREAD_GIL
+    MP_THREAD_GIL_EXIT();
     mp_thread_mutex_unlock(&self->mutex);
-    #endif
+    MP_THREAD_GIL_ENTER();
     return mp_const_none;
 }
 STATIC MP_DEFINE_CONST_FUN_OBJ_1(thread_lock_release_obj, thread_lock_release);