sd-event: make sure RT signals are not dropped

RT signals operate in a queue, and we should be careful to never merge
two queued signals into one. Hence, makes sure we only ever dequeue a
single signal at a time and leave the remaining ones queued in the
signalfd. In order to implement correct priorities for the signals
introduce one signalfd per priority, so that we only process the highest
priority signal at a time.

1 files changed, 65 insertions, 1 deletions

diff --git a/src/libsystemd/sd-event/test-event.c b/src/libsystemd/sd-event/test-event.c
index 408e1679a2..c092e56b7a 100644
--- a/src/libsystemd/sd-event/test-event.c
+++ b/src/libsystemd/sd-event/test-event.c
@@ -156,7 +156,7 @@ static int exit_handler(sd_event_source *s, void *userdata) {
         return 3;
 }
 
-int main(int argc, char *argv[]) {
+static void test_basic(void) {
         sd_event *e = NULL;
         sd_event_source *w = NULL, *x = NULL, *y = NULL, *z = NULL, *q = NULL, *t = NULL;
         static const char ch = 'x';
@@ -244,6 +244,70 @@ int main(int argc, char *argv[]) {
         safe_close_pair(b);
         safe_close_pair(d);
         safe_close_pair(k);
+}
+
+static int last_rtqueue_sigval = 0;
+static int n_rtqueue = 0;
+
+static int rtqueue_handler(sd_event_source *s, const struct signalfd_siginfo *si, void *userdata) {
+        last_rtqueue_sigval = si->ssi_int;
+        n_rtqueue ++;
+        return 0;
+}
+
+static void test_rtqueue(void) {
+        sd_event_source *u = NULL, *v = NULL, *s = NULL;
+        sd_event *e = NULL;
+
+        assert_se(sd_event_default(&e) >= 0);
+
+        assert_se(sigprocmask_many(SIG_BLOCK, NULL, SIGRTMIN+2, SIGRTMIN+3, SIGUSR2, -1) >= 0);
+        assert_se(sd_event_add_signal(e, &u, SIGRTMIN+2, rtqueue_handler, NULL) >= 0);
+        assert_se(sd_event_add_signal(e, &v, SIGRTMIN+3, rtqueue_handler, NULL) >= 0);
+        assert_se(sd_event_add_signal(e, &s, SIGUSR2, rtqueue_handler, NULL) >= 0);
+
+        assert_se(sd_event_source_set_priority(v, -10) >= 0);
+
+        assert(sigqueue(getpid(), SIGRTMIN+2, (union sigval) { .sival_int = 1 }) >= 0);
+        assert(sigqueue(getpid(), SIGRTMIN+3, (union sigval) { .sival_int = 2 }) >= 0);
+        assert(sigqueue(getpid(), SIGUSR2, (union sigval) { .sival_int = 3 }) >= 0);
+        assert(sigqueue(getpid(), SIGRTMIN+3, (union sigval) { .sival_int = 4 }) >= 0);
+        assert(sigqueue(getpid(), SIGUSR2, (union sigval) { .sival_int = 5 }) >= 0);
+
+        assert_se(n_rtqueue == 0);
+        assert_se(last_rtqueue_sigval == 0);
+
+        assert_se(sd_event_run(e, (uint64_t) -1) >= 1);
+        assert_se(n_rtqueue == 1);
+        assert_se(last_rtqueue_sigval == 2); /* first SIGRTMIN+3 */
+
+        assert_se(sd_event_run(e, (uint64_t) -1) >= 1);
+        assert_se(n_rtqueue == 2);
+        assert_se(last_rtqueue_sigval == 4); /* second SIGRTMIN+3 */
+
+        assert_se(sd_event_run(e, (uint64_t) -1) >= 1);
+        assert_se(n_rtqueue == 3);
+        assert_se(last_rtqueue_sigval == 3); /* first SIGUSR2 */
+
+        assert_se(sd_event_run(e, (uint64_t) -1) >= 1);
+        assert_se(n_rtqueue == 4);
+        assert_se(last_rtqueue_sigval == 1); /* SIGRTMIN+2 */
+
+        assert_se(sd_event_run(e, 0) == 0); /* the other SIGUSR2 is dropped, because the first one was still queued */
+        assert_se(n_rtqueue == 4);
+        assert_se(last_rtqueue_sigval == 1);
+
+        sd_event_source_unref(u);
+        sd_event_source_unref(v);
+        sd_event_source_unref(s);
+
+        sd_event_unref(e);
+}
+
+int main(int argc, char *argv[]) {
+
+        test_basic();
+        test_rtqueue();
 
         return 0;
 }