vpx_thread: use native windows cond var if available

BUG=b/29583578

original webp change:

commit 110ad5835ecd66995d0e7f66dca1b90dea595f5a
Author: James Zern <jzern@google.com>
Date:   Mon Nov 23 19:49:58 2015 -0800

    thread: use native windows cond var if available

    Vista / Server 2008 and up. no speed difference observed.

    Change-Id: Ice19704777cb679b290dc107a751a0f36dd0c0a9

100644 blob 4fc372b7bc6980a9ed3618c8cce5b67ed7b0f412 src/utils/thread.c
100644 blob 840831185502d42a3246e4b7ff870121c8064791 src/utils/thread.h

Change-Id: Iede7ae8a7184e4b17a4050b33956918fc84e15b5

1 files changed, 22 insertions, 0 deletions

diff --git a/vpx_util/vpx_thread.h b/vpx_util/vpx_thread.h
index 0964f4784..b63a01eba 100644
--- a/vpx_util/vpx_thread.h
+++ b/vpx_util/vpx_thread.h
@@ -33,11 +33,17 @@ extern "C" {
 #include <windows.h>  // NOLINT
 typedef HANDLE pthread_t;
 typedef CRITICAL_SECTION pthread_mutex_t;
+
+#if _WIN32_WINNT >= 0x0600  // Windows Vista / Server 2008 or greater
+#define USE_WINDOWS_CONDITION_VARIABLE
+typedef CONDITION_VARIABLE pthread_cond_t;
+#else
 typedef struct {
   HANDLE waiting_sem_;
   HANDLE received_sem_;
   HANDLE signal_event_;
 } pthread_cond_t;
+#endif  // _WIN32_WINNT >= 0x600
 
 //------------------------------------------------------------------------------
 // simplistic pthread emulation layer
@@ -97,15 +103,22 @@ static INLINE int pthread_mutex_destroy(pthread_mutex_t *const mutex) {
 // Condition
 static INLINE int pthread_cond_destroy(pthread_cond_t *const condition) {
   int ok = 1;
+#ifdef USE_WINDOWS_CONDITION_VARIABLE
+  (void)condition;
+#else
   ok &= (CloseHandle(condition->waiting_sem_) != 0);
   ok &= (CloseHandle(condition->received_sem_) != 0);
   ok &= (CloseHandle(condition->signal_event_) != 0);
+#endif
   return !ok;
 }
 
 static INLINE int pthread_cond_init(pthread_cond_t *const condition,
                                     void* cond_attr) {
   (void)cond_attr;
+#ifdef USE_WINDOWS_CONDITION_VARIABLE
+  InitializeConditionVariable(condition);
+#else
   condition->waiting_sem_ = CreateSemaphore(NULL, 0, MAX_DECODE_THREADS, NULL);
   condition->received_sem_ = CreateSemaphore(NULL, 0, MAX_DECODE_THREADS, NULL);
   condition->signal_event_ = CreateEvent(NULL, FALSE, FALSE, NULL);
@@ -115,11 +128,15 @@ static INLINE int pthread_cond_init(pthread_cond_t *const condition,
     pthread_cond_destroy(condition);
     return 1;
   }
+#endif
   return 0;
 }
 
 static INLINE int pthread_cond_signal(pthread_cond_t *const condition) {
   int ok = 1;
+#ifdef USE_WINDOWS_CONDITION_VARIABLE
+  WakeConditionVariable(condition);
+#else
   if (WaitForSingleObject(condition->waiting_sem_, 0) == WAIT_OBJECT_0) {
     // a thread is waiting in pthread_cond_wait: allow it to be notified
     ok = SetEvent(condition->signal_event_);
@@ -128,12 +145,16 @@ static INLINE int pthread_cond_signal(pthread_cond_t *const condition) {
     ok &= (WaitForSingleObject(condition->received_sem_, INFINITE) !=
            WAIT_OBJECT_0);
   }
+#endif
   return !ok;
 }
 
 static INLINE int pthread_cond_wait(pthread_cond_t *const condition,
                                     pthread_mutex_t *const mutex) {
   int ok;
+#ifdef USE_WINDOWS_CONDITION_VARIABLE
+  ok = SleepConditionVariableCS(condition, mutex, INFINITE);
+#else
   // note that there is a consumer available so the signal isn't dropped in
   // pthread_cond_signal
   if (!ReleaseSemaphore(condition->waiting_sem_, 1, NULL))
@@ -144,6 +165,7 @@ static INLINE int pthread_cond_wait(pthread_cond_t *const condition,
         WAIT_OBJECT_0);
   ok &= ReleaseSemaphore(condition->received_sem_, 1, NULL);
   pthread_mutex_lock(mutex);
+#endif
   return !ok;
 }
 #elif defined(__OS2__)