Make `timer_create(CLOCK_REALTIME)` autoconf test more reliable

I've noticed that on a platform with a coarse timer/scheduling
granularity of 10ms this autoconf tests fails to detect a working
`timer_create(CLOCK_REALTIME)`.

On AIX, this effectively means that intervals/timers are rounded up to
multiples of 10ms, so a 13ms delay is effectively a 20ms delay.

By using a 100ms timeout we are on the safe side.

Reviewers: austin, bgamari

Reviewed By: bgamari

Subscribers: thomie, erikd

Differential Revision: https://phabricator.haskell.org/D1483

1 files changed, 5 insertions, 4 deletions

diff --git a/aclocal.m4 b/aclocal.m4
index 2bf27bedf0..33f05e5a6f 100644
--- a/aclocal.m4
+++ b/aclocal.m4
@@ -1591,17 +1591,18 @@ int main(int argc, char *argv[])
         exit(2);
     }
 
+    tock = 0;
+
     it.it_value.tv_sec = 0;
-    it.it_value.tv_nsec = 1000000;
+    it.it_value.tv_nsec = 1000000; // 1ms
     it.it_interval = it.it_value;
     if (timer_settime(timer, 0, &it, NULL) != 0) {
         fprintf(stderr,"settime problem\n");
         exit(4);
     }
 
-    tock = 0;
-
-    usleep(3000);
+    // some environments have coarse scheduler/timer granularity of ~10ms and worse
+    usleep(100000); // 100ms
 
     if (!tock) {
         fprintf(stderr,"no CLOCK_REALTIME signal\n");