[Mesa-dev] [PATCH] gallium/util: don't let children of fork & exec inherit our thread affinity

[Nicholas Miell]

On 09/12/2018 05:40 PM, Marek Olšák wrote:
> +static void
> +util_set_full_cpu_affinity(void)
> +{
> +   cpu_set_t cpuset;
> +
> +   CPU_ZERO(&cpuset);
> +   for (unsigned i = 0; i < CPU_SETSIZE; i++)
> +      CPU_SET(i, &cpuset);
> +
> +   pthread_setaffinity_np(pthread_self(), sizeof(cpuset), &cpuset);
> +}
>  
>  static void
> -util_init_cache_number(void)
> +util_init_thread_pinning(void)
>  {
>     /* Get a semi-random number. */
>     int64_t t = os_time_get_nano();
>     L3_cache_number = (t ^ (t >> 8) ^ (t >> 16));
> +
> +   /* Reset thread affinity for all children of fork and exec to prevent
> +    * spawned processes and threads from inheriting the current thread's
> +    * affinity.
> +    *
> +    * What happens if a driver is unloaded and the app creates a thread?
> +    */
> +   pthread_atfork(NULL, NULL, util_set_full_cpu_affinity);
>  }
>  

You should probably save and restore the application's affinity mask
rather than assuming the mask is set to all CPUs.