On Thu, Dec 3, 2020 at 1:36 AM Andreas Rheinhardt < andreas.rheinha...@gmail.com> wrote:
> av_cpu_count() intends to emit a debug message containing the number of > logical cores when called the first time. The check currently works with > a static volatile int; yet this does not help at all in case of > concurrent accesses by multiple threads. So replace this with an > atomic_int. > > Signed-off-by: Andreas Rheinhardt <andreas.rheinha...@gmail.com> > --- > To test my patches I have modified avcodec_open2() to always open the > desired AVCodecContext simultaneously from two different threads [1]. > With this one easily runs into this issue when one uses a decoder with > FF_CODEC_CAP_INIT_THREADSAFE that supports threading. > > [1]: https://pastebin.com/a1uEuQ81 > > libavutil/cpu.c | 6 ++---- > 1 file changed, 2 insertions(+), 4 deletions(-) > > diff --git a/libavutil/cpu.c b/libavutil/cpu.c > index 52f6b9a3bf..7b8a9045ab 100644 > --- a/libavutil/cpu.c > +++ b/libavutil/cpu.c > @@ -274,7 +274,7 @@ int av_parse_cpu_caps(unsigned *flags, const char *s) > > int av_cpu_count(void) > { > - static volatile int printed; > + static atomic_int printed = 0; > > int nb_cpus = 1; > #if HAVE_WINRT > @@ -306,10 +306,8 @@ int av_cpu_count(void) > nb_cpus = sysinfo.dwNumberOfProcessors; > #endif > > - if (!printed) { > + if (!atomic_exchange_explicit(&printed, 1, memory_order_relaxed)) > av_log(NULL, AV_LOG_DEBUG, "detected %d logical cores\n", > nb_cpus); > - printed = 1; > - } > > return nb_cpus; > } > -- > 2.25.1 > > Will apply. - Andreas _______________________________________________ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org https://ffmpeg.org/mailman/listinfo/ffmpeg-devel To unsubscribe, visit link above, or email ffmpeg-devel-requ...@ffmpeg.org with subject "unsubscribe".
