Merge pull request #4554 from babsingh/unblock_signals_update

Only unblock an asynchronous signal if it is used

port/unix/omrsignal.c

@@ -272,7 +272,7 @@ static void masterSynchSignalHandler(int signal, siginfo_t *sigInfo, void *conte
 static void masterASynchSignalHandler(int signal, siginfo_t *sigInfo, void *contextInfo);
 #endif /* defined(S390) && defined(LINUX) */
 
-static int32_t unblockSignals(void);
+static int32_t unblockSignal(int signal);
 
 static void setBitMaskSignalsWithHandlers(uint32_t flags);
 static void unsetBitMaskSignalsWithHandlers(uint32_t flags);
@@ -1269,6 +1269,18 @@ registerSignalHandlerWithOS(OMRPortLibrary *portLibrary, uint32_t portLibrarySig
 		return OMRPORT_SIG_ERROR;
 	}
 
+	/* If a process has blocked an asynchronous signal, then the signal stays
+	 * blocked in the sub-processes across fork(s) and exec(s). A blocked
+	 * signal prevents its OS signal handler to be invoked. A signal is
+	 * unblocked as an OS signal handler is installed for it in case a
+	 * parent process has blocked it.
+	 */
+	if (OMR_ARE_ALL_BITS_SET(OMRPORT_SIG_FLAG_SIGALLASYNC, portLibrarySignalNo)) {
+		if (0 != unblockSignal(unixSignalNo)) {
+			return OMRPORT_SIG_ERROR;
+		}
+	}
+
 	memset(&newAction, 0, sizeof(struct sigaction));
 
 	/* Do not block any signals. */
@@ -1606,16 +1618,6 @@ initializeSignalTools(OMRPortLibrary *portLibrary)
 	}
 #endif /* !defined(J9ZOS390) */
 
-	/* If a process has blocked signals, then the signals stay blocked in the
-	 * sub-processes across fork(s) and exec(s). Blocked signals prevent signal
-	 * handlers to be invoked. Signals listed in signalMap should be unblocked
-	 * during initialization in case a parent process has blocked any of those
-	 * signals.
-	 */
-	if (0 != unblockSignals()) {
-		return -1;
-	}
-
 #if defined(OMR_PORT_ASYNC_HANDLER)
 	if (J9THREAD_SUCCESS != createThreadWithCategory(
 			&asynchSignalReporterThread,
@@ -1870,19 +1872,18 @@ omrsig_chain_at_shutdown_and_exit(struct OMRPortLibrary *portLibrary)
 #endif /* defined(OMRPORT_OMRSIG_SUPPORT) */
 
 /**
- * This function will unblock signals listed in signalMap by changing the
- * signal mask of the calling thread. This function should only be called
- * during initialization from the main thread and before creation of other
- * threads.
+ * This function will unblock a signal by changing the signal mask of the
+ * calling thread. This function is only invoked while registering a signal
+ * handler with the OS (registerSignalHandlerWithOS), which is protected by
+ * registerHandlerMonitor for synchronization.
  *
- * @param[in] void
+ * @param[in] signal the signal to be unblocked
  *
  * @return 0 on success and non-zero on failure
  */
 static int32_t
-unblockSignals(void) {
+unblockSignal(int signal) {
 	int32_t rc = 0;
-	int i = 0;
 	sigset_t signalSet;
 
 	rc = sigemptyset(&signalSet);
@@ -1891,18 +1892,13 @@ unblockSignals(void) {
 		goto exit;
 	}
 
-	/* Iterate through all signals listed in signalMap. */
-	for (i = 0; i < sizeof(signalMap) / sizeof(signalMap[0]); i++) {
-		/* Add the current signal to the signal set. */
-		int currentSignal = signalMap[i].unixSignalNo;
-		rc = sigaddset(&signalSet, currentSignal);
-		if (0 != rc) {
-			Trc_PRT_signal_unblockSignals_sigaddset_failed(currentSignal, rc, errno);
-			goto exit;
-		}
+	rc = sigaddset(&signalSet, signal);
+	if (0 != rc) {
+		Trc_PRT_signal_unblockSignals_sigaddset_failed(signal, rc, errno);
+		goto exit;
 	}
 
-	/* Unblock the signals listed in signalMap. */
+	/* Unblock the signal. */
 	rc = pthread_sigmask(SIG_UNBLOCK, &signalSet, NULL);
 	if (0 != rc) {
 		Trc_PRT_signal_unblockSignals_pthread_sigmask_failed(rc, errno);