igt/gem_sync: Enforce a timeout of 20s

The sync test is supposed to complete in 10s. But some bugs cause it to
run very, very slowly. As a defence against those, terminate the test if
we wait for more than 20s.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>

lib/igt_core.c

@@ -1131,6 +1131,9 @@ void igt_exit(void)
 	kmsg(KERN_INFO "%s: exiting, ret=%d\n", command_str, igt_exitcode);
 	igt_debug("Exiting with status code %d\n", igt_exitcode);
 
+	for (int c = 0; c < num_test_children; c++)
+		kill(test_children[c], SIGKILL);
+
 	if (!test_with_subtests) {
 		struct timespec now;
 		const char *result;
@@ -1401,6 +1404,20 @@ void igt_waitchildren(void)
 		igt_fail(err);
 }
 
+/**
+ * igt_waitchildren_timeout:
+ *
+ * Wait for all children forked with igt_fork, for a maximum of @seconds.
+ *
+ * Wraps igt_waitchildren() and igt_set_timeout()
+ */
+void igt_waitchildren_timeout(int seconds, const char *reason)
+{
+	igt_set_timeout(seconds, reason);
+	igt_waitchildren();
+	igt_reset_timeout();
+}
+
 /* exit handler code */
 #define MAX_SIGNALS		32
 #define MAX_EXIT_HANDLERS	10

lib/igt_core.h

@@ -610,6 +610,7 @@ bool __igt_fork(void);
 	for (int child = 0; child < (num_children); child++) \
 		for (; __igt_fork(); exit(0))
 void igt_waitchildren(void);
+void igt_waitchildren_timeout(int seconds, const char *reason);
 
 /**
  * igt_helper_process:

tests/gem_sync.c

@@ -155,7 +155,7 @@ sync_ring(int fd, unsigned ring, int num_children)
 
 		gem_close(fd, object.handle);
 	}
-	igt_waitchildren();
+	igt_waitchildren_timeout(20, NULL);
 	igt_assert_eq(intel_detect_and_clear_missed_interrupts(fd), 0);
 }