commit eda23a1c9cf89d22b15d838fdf46042b51a3e4ca
author Robert O'Callahan <robert@ocallahan.org> Wed Sep 20 00:23:58 2023 +1200
committer Robert O'Callahan <robert@ocallahan.org> Wed Sep 20 00:24:23 2023 +1200
tree c5a6e71c17fcf402c0fb4ba6bd3ce0bfa26a8148
parent e43acfb5f1ae98c49d21daa5eb7ceb1d8bc83c6b

Close race condition in ppoll test where SIGALRM was delivered before we actually reached ppoll

This seems to be what triggered the intermittent failure in https://buildkite.com/julialang/rr/builds/1395#018aad32-437b-4d71-ac76-a211b2c5dc18

src/test/ppoll.c

diff --git a/src/test/ppoll.c b/src/test/ppoll.c
index 3fe055f..19af545 100644
--- a/src/test/ppoll.c
+++ b/src/test/ppoll.c
@@ -51,6 +51,15 @@
   pfd.events = POLLIN;
   for (i = 0; i < NUM_ITERATIONS; i++) {
     int ret;
+    sigset_t before_sigset;
+    sigset_t sigalrm_blocked_sigset;
+    sigemptyset(&sigalrm_blocked_sigset);
+    sigaddset(&sigalrm_blocked_sigset, SIGALRM);
+    /* Block SIGALRM before we call our_ualarm because we don't want it
+       to go off early. */
+    ret = sigprocmask(SIG_SETMASK, &sigalrm_blocked_sigset, &before_sigset);
+    test_assert(ret == 0);
+    test_assert(!sigismember(&before_sigset, SIGALRM));
 
     atomic_printf("iteration %d\n", i);
     if (i % 2 == 0) {
@@ -60,11 +69,6 @@
       return 0;
     }
 
-    sigset_t before_sigset;
-    ret = sigprocmask(SIG_BLOCK, NULL, &before_sigset);
-    test_assert(ret == 0);
-    test_assert(!sigismember(&before_sigset, SIGALRM));
-
     t.tv_sec = 1;
     t.tv_nsec = 0;
 
@@ -82,7 +86,7 @@
 
     /* Validate that the signal mask got reset */
     sigset_t after_sigset;
-    ret = sigprocmask(SIG_BLOCK, NULL, &after_sigset);
+    ret = sigprocmask(SIG_SETMASK, &before_sigset, &after_sigset);
     test_assert(ret == 0);
     test_assert(!sigismember(&after_sigset, SIGCHLD));
   }