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authorHendrik Leppkes <h.leppkes@gmail.com>2015-10-07 15:10:59 +0200
committerLuca Barbato <lu_zero@gentoo.org>2015-10-07 18:45:50 +0200
commitb22693b06d1e5d73454a65c203b4d31c1ca5b69a (patch)
treedaee9d44d9b3912ed9df54b1bcb1616ea570889d /compat
parent8b830ee9a26d47b138f12a82085cdb372f407f1e (diff)
downloadffmpeg-b22693b06d1e5d73454a65c203b4d31c1ca5b69a.tar.gz
w32pthreads: Add pthread_once emulation
The emulation uses native InitOnce* APIs on Windows Vista+, and a lock-free/allocation-free approach using atomics and spinning for Windows XP. Signed-off-by: Luca Barbato <lu_zero@gentoo.org>
Diffstat (limited to 'compat')
-rw-r--r--compat/w32pthreads.h73
1 files changed, 73 insertions, 0 deletions
diff --git a/compat/w32pthreads.h b/compat/w32pthreads.h
index 3748289809..a1cb396d6e 100644
--- a/compat/w32pthreads.h
+++ b/compat/w32pthreads.h
@@ -118,6 +118,20 @@ static inline int pthread_mutex_unlock(pthread_mutex_t *m)
}
#if _WIN32_WINNT >= 0x0600
+
+typedef INIT_ONCE pthread_once_t;
+#define PTHREAD_ONCE_INIT INIT_ONCE_STATIC_INIT
+
+static av_unused int pthread_once(pthread_once_t *once_control, void (*init_routine)(void))
+{
+ BOOL pending = FALSE;
+ InitOnceBeginInitialize(once_control, 0, &pending, NULL);
+ if (pending)
+ init_routine();
+ InitOnceComplete(once_control, 0, NULL);
+ return 0;
+}
+
static inline void pthread_cond_init(pthread_cond_t *cond, const void *unused_attr)
{
InitializeConditionVariable(cond);
@@ -146,8 +160,63 @@ static inline void pthread_cond_signal(pthread_cond_t *cond)
}
#else // _WIN32_WINNT < 0x0600
+/* for pre-Windows 6.0 platforms, define INIT_ONCE struct,
+ * compatible to the one used in the native API */
+
+typedef union pthread_once_t {
+ void * Ptr; ///< For the Windows 6.0+ native functions
+ LONG state; ///< For the pre-Windows 6.0 compat code
+} pthread_once_t;
+
+#define PTHREAD_ONCE_INIT {0}
+
+/* function pointers to init once API on windows 6.0+ kernels */
+static BOOL (WINAPI *initonce_begin)(pthread_once_t *lpInitOnce, DWORD dwFlags, BOOL *fPending, void **lpContext);
+static BOOL (WINAPI *initonce_complete)(pthread_once_t *lpInitOnce, DWORD dwFlags, void *lpContext);
+
+/* pre-Windows 6.0 compat using a spin-lock */
+static inline void w32thread_once_fallback(LONG volatile *state, void (*init_routine)(void))
+{
+ switch (InterlockedCompareExchange(state, 1, 0)) {
+ /* Initial run */
+ case 0:
+ init_routine();
+ InterlockedExchange(state, 2);
+ break;
+ /* Another thread is running init */
+ case 1:
+ while (1) {
+ MemoryBarrier();
+ if (*state == 2)
+ break;
+ Sleep(0);
+ }
+ break;
+ /* Initialization complete */
+ case 2:
+ break;
+ }
+}
+
+static av_unused int pthread_once(pthread_once_t *once_control, void (*init_routine)(void))
+{
+ /* Use native functions on Windows 6.0+ */
+ if (initonce_begin && initonce_complete) {
+ BOOL pending = FALSE;
+ initonce_begin(once_control, 0, &pending, NULL);
+ if (pending)
+ init_routine();
+ initonce_complete(once_control, 0, NULL);
+ return 0;
+ }
+
+ w32thread_once_fallback(&once_control->state, init_routine);
+ return 0;
+}
+
/* for pre-Windows 6.0 platforms we need to define and use our own condition
* variable and api */
+
typedef struct win32_cond_t {
pthread_mutex_t mtx_broadcast;
pthread_mutex_t mtx_waiter_count;
@@ -306,6 +375,10 @@ static av_unused void w32thread_init(void)
(void*)GetProcAddress(kernel_dll, "WakeConditionVariable");
cond_wait =
(void*)GetProcAddress(kernel_dll, "SleepConditionVariableCS");
+ initonce_begin =
+ (void*)GetProcAddress(kernel_dll, "InitOnceBeginInitialize");
+ initonce_complete =
+ (void*)GetProcAddress(kernel_dll, "InitOnceComplete");
#endif
}