On Wed, Oct 7, 2015 at 7:06 PM, Matt Oliver <protogo...@gmail.com> wrote: > On 8 October 2015 at 03:29, Hendrik Leppkes <h.lepp...@gmail.com> wrote: > >> On Wed, Oct 7, 2015 at 6:23 PM, Matt Oliver <protogo...@gmail.com> wrote: >> > On 6 October 2015 at 21:36, Hendrik Leppkes <h.lepp...@gmail.com> wrote: >> > >> >> The emulation uses native InitOnce* APIs on Windows Vista+, and a >> >> lock-free/allocation-free approach using atomics and spinning for >> Windows >> >> XP. >> >> --- >> >> >> >> This is in preparation to use pthread_once for global static init >> >> functions, >> >> and eventually removing the global lock in avcodec_open2 >> >> >> >> compat/w32pthreads.h | 68 >> >> ++++++++++++++++++++++++++++++++++++++++++++++++++++ >> >> 1 file changed, 68 insertions(+) >> >> >> >> diff --git a/compat/w32pthreads.h b/compat/w32pthreads.h >> >> index deb1c53..8523976 100644 >> >> --- a/compat/w32pthreads.h >> >> +++ b/compat/w32pthreads.h >> >> @@ -154,6 +154,19 @@ static inline int >> pthread_cond_signal(pthread_cond_t >> >> *cond) >> >> return 0; >> >> } >> >> >> >> +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; >> >> +} >> >> + >> >> #else // _WIN32_WINNT < 0x0600 >> >> /* for pre-Windows 6.0 platforms we need to define and use our own >> >> condition >> >> * variable and api */ >> >> @@ -304,6 +317,57 @@ static av_unused int >> >> pthread_cond_signal(pthread_cond_t *cond) >> >> pthread_mutex_unlock(&win32_cond->mtx_broadcast); >> >> return 0; >> >> } >> >> + >> >> +/* 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); >> >> + >> >> +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; >> >> + } >> >> + >> >> + /* pre-Windows 6.0 compat using a spin-lock */ >> >> + switch (InterlockedCompareExchange(&once_control->state, 1, 0)) >> >> + { >> >> + /* Initial run */ >> >> + case 0: >> >> + init_routine(); >> >> + InterlockedExchange(&once_control->state, 2); >> >> + break; >> >> + /* Another thread is running init */ >> >> + case 1: >> >> + while (1) { >> >> + MemoryBarrier(); >> >> + if (once_control->state == 2) >> >> + break; >> >> + Sleep(0); >> >> + } >> >> + break; >> >> + /* Initialization complete */ >> >> + case 2: >> >> + break; >> >> + } >> >> + return 0; >> >> +} >> >> #endif >> >> >> >> static av_unused void w32thread_init(void) >> >> @@ -319,6 +383,10 @@ 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 >> >> >> >> } >> >> -- >> >> 2.5.3.windows.1 >> > >> > >> > LGTM >> >> There is a new version of the patch which also solves the >> w32thread_init mess, so this one isn't the final version anymore. >> Current working version is here: >> https://github.com/Nevcairiel/FFmpeg/commits/pthread_once >> >> > This looks better. > So by win32thread_init mess im assuming your referring to a need to have > called it before hand. Given that youve added it to the only 2 functions > that need it then doesnt that mean that win32thread_init be completely > removed from all other code and only used locally in w32pthread.h and only > when WIN32_WINNT<0x600.
Yes, it can be removed in a follow up commit. _______________________________________________ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org http://ffmpeg.org/mailman/listinfo/ffmpeg-devel