[PATCH i-g-t 4/4] lib/kunit: Time out promptly on missing KTAP report

[Janusz Krzysztofik]

If a test provides a subtest name that doesn't match any test suites
provided by the requested KUnit test module then no KTAP report appears in
dmesg, not even an empty one as one may expect.  As a consequence, we now
loop endlessly around reading potential lines of the missing report from
/dev/kmsg, until killed by IGT runner on timeout.

When trying to collect names of test cases from a KTAP report generated in
all skip mode, set an alarm that fires up 10 seconds after we start
waiting for the report, interrupts blocking read() if pending, and
terminates the subtest with SKIP result.

As soon as we have collected a non-empty list of test cases, there should
be no need to set up an extra timeout before starting to extract and parse
a KTAP report with actual results from execution of those test cases.

Suggested-by: Kamil Konieczny <kamil.konieczny at linux.intel.com>
Signed-off-by: Janusz Krzysztofik <janusz.krzysztofik at linux.intel.com>
---
 lib/igt_kmod.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/lib/igt_kmod.c b/lib/igt_kmod.c
index 8a6824ea7e..f0e4d5ec76 100644
--- a/lib/igt_kmod.c
+++ b/lib/igt_kmod.c
@@ -1204,12 +1204,19 @@ static void __igt_kunit_legacy(struct igt_ktest *tst,
 	igt_skip_on_f(ret, "KTAP parser failed\n");
 }
 
+static void kunit_get_tests_timeout(int signal)
+{
+	igt_skip("Timed out while trying to extract a list of KUnit test cases from /dev/kmsg\n");
+}
+
 static bool kunit_get_tests(struct igt_list_head *tests,
 			    struct igt_ktest *tst,
 			    const char *suite,
 			    const char *opts,
 			    struct igt_ktap_results **ktap)
 {
+	struct sigaction sigalrm = { .sa_handler = kunit_get_tests_timeout, },
+			 *saved;
 	struct igt_ktap_result *r, *rn;
 	unsigned long taints;
 	int flags, err;
@@ -1239,10 +1246,16 @@ static bool kunit_get_tests(struct igt_list_head *tests,
 	*ktap = igt_ktap_alloc(tests);
 	igt_require(*ktap);
 
+	igt_skip_on(sigaction(SIGALRM, &sigalrm, saved));
+	alarm(10);
+
 	do
 		err = kunit_kmsg_result_get(tests, NULL, tst->kmsg, *ktap);
 	while (err == -EINPROGRESS);
 
+	alarm(0);
+	igt_debug_on(sigaction(SIGALRM, saved, NULL));
+
 	igt_ktap_free(ktap);
 
 	igt_skip_on_f(err,
-- 
2.43.0