On 8 October 2015 at 04:15, Hendrik Leppkes <h.lepp...@gmail.com> wrote:
> 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.
OK, I was just checking if that was the plan or not. Looks good to me.
_______________________________________________
ffmpeg-devel mailing list
ffmpeg-devel@ffmpeg.org
http://ffmpeg.org/mailman/listinfo/ffmpeg-devel
