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avutil/cpu: Fix race condition in av_cpu_count()
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.rheinhardt@gmail.com>
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@ -274,7 +274,7 @@ int av_parse_cpu_caps(unsigned *flags, const char *s)
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int av_cpu_count(void)
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{
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static volatile int printed;
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static atomic_int printed = ATOMIC_VAR_INIT(0);
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int nb_cpus = 1;
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#if HAVE_WINRT
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@ -306,10 +306,8 @@ int av_cpu_count(void)
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nb_cpus = sysinfo.dwNumberOfProcessors;
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#endif
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if (!printed) {
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if (!atomic_exchange_explicit(&printed, 1, memory_order_relaxed))
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av_log(NULL, AV_LOG_DEBUG, "detected %d logical cores\n", nb_cpus);
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printed = 1;
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}
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return nb_cpus;
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}
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