yield.c

   1 /*
   2  * Copyright (C) 2012-2020 all contributors <cmogstored-public@yhbt.net>
   3  * License: GPL-3.0+ <https://www.gnu.org/licenses/gpl-3.0.txt>
   4  */
   5 #include "cmogstored.h"
   6 #ifndef HAVE_PTHREAD_YIELD
   7 #  define pthread_yield() (void)sched_yield()
   8 #endif
   9
  10 /*
  11  * pthread_yield may migrate us to the same CPU as the task we're waiting
  12  * on, so just keep yielding for every CPU we have as this throttles
  13  * our ability to spam SIGURG.  This means the threads we're trying to
  14  * gracefully kill off can finish their work and check their mog_do_quit
  15  * flag sooner
  16  *
  17  * We only use this as a last resort when normal wakeups/notifications
  18  * are not usable (e.g. recovering from out-of-resource problems)
  19  */
  20 void mog_yield(void)
  21 {
  22         static unsigned long nproc_all;
  23         unsigned long i;
  24
  25         if (!nproc_all)
  26                 nproc_all = num_processors(NPROC_ALL) * 2;
  27         for (i = 0; i < nproc_all; i++)
  28                 pthread_yield();
  29 }