Improve gdb.threads/attach-many-short-lived-threads.exp timeout handling

The buildbot shows that this test is still racy, and occasionally
fails with time outs on some machines.  I'd like to get major issues
with load out of the way.

The test currently exits after 180s, which is just a random number,
that has no relation to what the .exp file considers a time out.  This
commit makes the program wait a bit longer than what the .exp file
considers a time out, and, resets the timer for each iteration.

Tested on x86_64 Fedora 20, native and extended-remote gdbserver.

gdb/testsuite/
2015-02-06  Pedro Alves  <palves@redhat.com>

	* gdb.threads/attach-many-short-lived-threads.c (SECONDS): New
	macro.
	(seconds_left, again): New globals.
	(main): Wait seconds_left in a 1-second sleep loop instead of
	sleeping 180 seconds.  If 'again' is set, reset the seconds
	counter.
	* gdb.threads/attach-many-short-lived-threads.exp (test): Set
	'again' in the inferior before detaching.  Print the seconds left.
	(options): New global.
	(top level): Build program with	-DTIMEOUT=$timeout.

2 files changed, 38 insertions, 4 deletions

diff --git a/gdb/testsuite/gdb.threads/attach-many-short-lived-threads.c b/gdb/testsuite/gdb.threads/attach-many-short-lived-threads.c
index 001f2ff..4a75022 100644
--- a/gdb/testsuite/gdb.threads/attach-many-short-lived-threads.c
+++ b/gdb/testsuite/gdb.threads/attach-many-short-lived-threads.c
@@ -113,6 +113,17 @@ detached_fn (void *arg)
   return NULL;
 }
 
+/* Allow for as much timeout as DejaGnu wants, plus a bit of
+   slack.  */
+#define SECONDS (TIMEOUT + 20)
+
+/* We'll exit after this many seconds.  */
+unsigned int seconds_left = SECONDS;
+
+/* GDB sets this whenever it's about to start a new detach/attach
+   sequence.  We react by resetting the seconds left counter.  */
+volatile int again = 0;
+
 int
 main (int argc, char *argv[])
 {
@@ -144,8 +155,20 @@ main (int argc, char *argv[])
       create_thread (&detached_attr, detached_fn, NULL);
     }
 
-  /* Long enough for all the attach/detach sequences done by the .exp
-     file.  */
-  sleep (180);
+  /* Exit after a while if GDB is gone/crashes.  But wait long enough
+     for one attach/detach sequence done by the .exp file.  */
+  while (--seconds_left > 0)
+    {
+      sleep (1);
+
+      if (again)
+	{
+	  /* GDB should be reattaching soon.  Restart the timer.  */
+	  again = 0;
+	  seconds_left = SECONDS;
+	}
+    }
+
+  printf ("timeout, exiting\n");
   return 0;
 }
diff --git a/gdb/testsuite/gdb.threads/attach-many-short-lived-threads.exp b/gdb/testsuite/gdb.threads/attach-many-short-lived-threads.exp
index 96c98ea..2c2236d 100644
--- a/gdb/testsuite/gdb.threads/attach-many-short-lived-threads.exp
+++ b/gdb/testsuite/gdb.threads/attach-many-short-lived-threads.exp
@@ -112,6 +112,12 @@ proc test {} {
 	    }
 
 	    if {$attempt < $attempts} {
+		# Kick the time out timer for another round.
+		gdb_test "print again = 1" " = 1" "reset timer in the inferior"
+		# Show the time we had left in the logs, in case
+		# something goes wrong.
+		gdb_test "print seconds_left" " = .*"
+
 		gdb_test "detach" "Detaching from.*"
 	    } else {
 		gdb_test "kill" "" "kill process" "Kill the program being debugged.*y or n. $" "y"
@@ -125,7 +131,12 @@ proc test {} {
     remote_exec target "kill -9 ${testpid}"
 }
 
-if {[prepare_for_testing "failed to prepare" $testfile $srcfile {debug pthreads}] == -1} {
+# The test program exits after a while, in case GDB crashes.  Make it
+# wait at least as long as we may wait before declaring a time out
+# failure.
+set options { "additional_flags=-DTIMEOUT=$timeout" debug pthreads }
+
+if {[prepare_for_testing "failed to prepare" $testfile $srcfile $options] == -1} {
     return -1
 }