tests/wq_block_handoff.c

   1 #include <dispatch/dispatch.h>
   2 #include <sys/sysctl.h>
   3 #include <stdio.h>
   4
   5 static int x = 0;
   6 static int y = 0;
   7
   8 int main(void)
   9 {
  10         /* found in <rdar://problem/16326400> 12A216: Spotlight takes a long time to show results */
  11
  12         /* we need to start up NCPU-1 threads in a given bucket, then fire up one more at a separate
  13          * priority.
  14          *
  15          * each of these waiters needs to be non-blocked until the point where dispatch wants to
  16          * request a new thread.
  17          *
  18          * if dispatch ever fixes sync_barrier -> sync handoff to not require an extra thread,
  19          * then this test will never fail and will be invalid.
  20          */
  21
  22         printf("[TEST] barrier_sync -> async @ ncpu threads\n");
  23
  24         dispatch_semaphore_t sema = dispatch_semaphore_create(0);
  25
  26         int ncpu = 1;
  27         size_t sz = sizeof(ncpu);
  28         sysctlbyname("hw.ncpu", &ncpu, &sz, NULL, 0);
  29         printf("starting up %d waiters.\n", ncpu);
  30
  31         dispatch_queue_t q = dispatch_queue_create("moo", DISPATCH_QUEUE_CONCURRENT);
  32         dispatch_barrier_sync(q, ^{
  33                 dispatch_async(q, ^{
  34                         printf("async.\n");
  35                         dispatch_semaphore_signal(sema);
  36                 });
  37                 for (int i=0; i<ncpu-1; i++) {
  38                         dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, 0), ^{
  39                                 printf("waiter %d* up.\n", i);
  40                                 while (y == 0) { };
  41                         });
  42                 }
  43                 dispatch_async(dispatch_get_global_queue(0, 0), ^{
  44                         printf("waiter %d up.\n", ncpu-1);
  45                         while (x == 0) { };
  46                         printf("waiter %d idle.\n", ncpu-1);
  47                         usleep(1000);
  48                         dispatch_sync(q, ^{ printf("quack %d\n", ncpu-1); });
  49                 });
  50                 printf("waiting...\n");
  51                 sleep(1);
  52                 printf("done.\n");
  53         });
  54
  55         x = 1;
  56         int rv = dispatch_semaphore_wait(sema, dispatch_time(DISPATCH_TIME_NOW, 2ull * NSEC_PER_SEC));
  57         printf("[%s] barrier_sync -> async completed\n", rv == 0 ? "PASS" : "FAIL");
  58
  59         return rv;
  60 }