[FFmpeg-devel] [PATCH] winrt: multithreading support

[Hendrik Leppkes]

On Thu, Oct 1, 2015 at 9:05 PM, wm4 <nfxjfg at googlemail.com> wrote:
> On Fri, 2 Oct 2015 02:58:52 +0800
> Wang Bin <wbsecg1 at gmail.com> wrote:
>
>> From b8b5ad2d65107781116666c2a03ae5cfbe727ee6 Mon Sep 17 00:00:00 2001
>> From: wang-bin <wbsecg1 at gmail.com>
>> Date: Tue, 29 Sep 2015 18:11:03 +0800
>> Subject: [PATCH] winrt: multithreading support
>>
>> _beginthreadex is for desktop only. CreateThread is available for windows store apps on windows (and phone) 8.1 and later. http://msdn.microsoft.com/en-us/library/ms682453%28VS.85%29.aspx
>> ---
>>  compat/w32pthreads.h | 14 ++++++++++++++
>>  configure            |  4 ++++
>>  libavutil/cpu.c      | 14 +++++++++++++-
>>  3 files changed, 31 insertions(+), 1 deletion(-)
>>
>> diff --git a/compat/w32pthreads.h b/compat/w32pthreads.h
>> index deb1c53..7491cab 100644
>> --- a/compat/w32pthreads.h
>> +++ b/compat/w32pthreads.h
>> @@ -37,7 +37,16 @@
>>
>>  #define WIN32_LEAN_AND_MEAN
>>  #include <windows.h>
>> +#ifdef WINAPI_FAMILY
>> +#include <winapifamily.h>
>> +#if !WINAPI_FAMILY_PARTITION(WINAPI_PARTITION_DESKTOP)
>> +#define TARGET_OS_WINRT
>> +#endif
>> +#endif
>> +#ifndef TARGET_OS_WINRT
>>  #include <process.h>
>> +#endif
>> +
>>
>>  #include "libavutil/attributes.h"
>>  #include "libavutil/common.h"
>> @@ -82,8 +91,13 @@ static av_unused int pthread_create(pthread_t *thread, const void *unused_attr,
>>  {
>>      thread->func   = start_routine;
>>      thread->arg    = arg;
>> +#ifndef TARGET_OS_WINRT
>>      thread->handle = (void*)_beginthreadex(NULL, 0, win32thread_worker, thread,
>>                                             0, NULL);
>> +#else
>> +    thread->handle = (void*)CreateThread(NULL, 0, win32thread_worker, thread,
>> +                                           0, NULL);
>> +#endif
>
> Why can't it always use CreateThread? This looks very suspicious.

MSDN warns about using CreateThread with C code, something with the
CRT init, and recommend _beginthreadex instead.
Using CreateThread on WinRT seems a bit fishy for the same reason.

>
>>      return !thread->handle;
>>  }
>>
>> diff --git a/configure b/configure
>> index 361c024..08d0d5d 100755
>> --- a/configure
>> +++ b/configure
>> @@ -5189,6 +5189,10 @@ check_type "vdpau/vdpau.h" "VdpPictureInfoHEVC"
>>  if ! disabled w32threads && ! enabled pthreads; then
>>      check_func_headers "windows.h process.h" _beginthreadex &&
>>          enable w32threads || disable w32threads
>> +    if ! enabled w32threads; then
>> +        check_func_headers "windows.h" CreateThread &&
>> +            enable w32threads || disable w32threads
>> +    fi
>>  fi
>>
>>  # check for some common methods of building with pthread support
>> diff --git a/libavutil/cpu.c b/libavutil/cpu.c
>> index 780368d..c562e86 100644
>> --- a/libavutil/cpu.c
>> +++ b/libavutil/cpu.c
>> @@ -30,8 +30,14 @@
>>  #endif
>>  #include <sched.h>
>>  #endif
>> -#if HAVE_GETPROCESSAFFINITYMASK
>> +#if HAVE_WINDOWS_H
>>  #include <windows.h>
>> +#ifdef WINAPI_FAMILY
>> +#include <winapifamily.h>
>> +#if !WINAPI_FAMILY_PARTITION(WINAPI_PARTITION_DESKTOP)
>> +#define TARGET_OS_WINRT
>> +#endif
>> +#endif
>>  #endif
>>  #if HAVE_SYSCTL
>>  #if HAVE_SYS_PARAM_H
>> @@ -253,6 +259,9 @@ int av_cpu_count(void)
>>      static volatile int printed;
>>
>>      int nb_cpus = 1;
>> +#ifdef TARGET_OS_WINRT
>> +    SYSTEM_INFO sysinfo;
>> +#endif
>>  #if HAVE_SCHED_GETAFFINITY && defined(CPU_COUNT)
>>      cpu_set_t cpuset;
>>
>> @@ -274,6 +283,9 @@ int av_cpu_count(void)
>>      nb_cpus = sysconf(_SC_NPROC_ONLN);
>>  #elif HAVE_SYSCONF && defined(_SC_NPROCESSORS_ONLN)
>>      nb_cpus = sysconf(_SC_NPROCESSORS_ONLN);
>> +#elif defined(TARGET_OS_WINRT)
>> +    GetNativeSystemInfo(&sysinfo);
>> +    nb_cpus = sysinfo.dwNumberOfProcessors;
>>  #endif
>
> You could avoid the first ifdef by opening a new scope.
>
> What's the difference to GetProcessAffinityMask() (which is apparently
> not available on WinRT)?

GetProcessAffinityMask takes into account the settings the user makes,
ie. he could tell the process to always run on a particular set of
cores only.

>
>>
>>      if (!printed) {
>
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