sighook: New sigreset() function to reset all handlers

2 files changed, 45 insertions, 3 deletions

diff --git a/src/sighook.c b/src/sighook.c
index a1fc30d..820044c 100644
--- a/src/sighook.c
+++ b/src/sighook.c
@@ -525,6 +525,18 @@ static void sigdispatch(int sig, siginfo_t *info, void *context) {
 	errno = error;
 }
 
+/** A saved signal handler, for sigreset() to restore. */
+struct sigsave {
+	struct rcu_node node;
+	int sig;
+	struct sigaction action;
+};
+
+/** The list of saved signal handlers. */
+static struct rcu_list saved;
+/** `saved` initialization status (since rcu_list_init() isn't atomic). */
+static atomic bool initialized = false;
+
 /** Make sure our signal handler is installed for a given signal. */
 static int siginit(int sig) {
 #ifdef SA_RESTART
@@ -539,9 +551,8 @@ static int siginit(int sig) {
 	};
 
 	static sigset_t signals;
-	static bool initialized = false;
 
-	if (!initialized) {
+	if (!load(&initialized, relaxed)) {
 		if (sigemptyset(&signals) != 0
 		    || sigemptyset(&action.sa_mask) != 0) {
 			return -1;
@@ -551,7 +562,8 @@ static int siginit(int sig) {
 			rcu_list_init(&sighooks[i]);
 		}
 
-		initialized = true;
+		rcu_list_init(&saved);
+		store(&initialized, true, release);
 	}
 
 	int installed = sigismember(&signals, sig);
@@ -561,6 +573,18 @@ static int siginit(int sig) {
 		return 0;
 	}
 
+	struct sigsave *save = ALLOC(struct sigsave);
+	if (!save) {
+		return -1;
+	}
+
+	save->sig = sig;
+	if (sigaction(sig, NULL, &save->action) != 0) {
+		free(save);
+		return -1;
+	}
+	rcu_list_append(&saved, &save->node);
+
 	if (sigaction(sig, &action, NULL) != 0) {
 		return -1;
 	}
@@ -639,3 +663,13 @@ void sigunhook(struct sighook *hook) {
 
 	free(hook);
 }
+
+int sigreset(void) {
+	for_rcu (struct sigsave, save, &saved) {
+		if (sigaction(save->sig, &save->action, NULL) != 0) {
+			return -1;
+		}
+	}
+
+	return 0;
+}
diff --git a/src/sighook.h b/src/sighook.h
index 87bba4e..7149229 100644
--- a/src/sighook.h
+++ b/src/sighook.h
@@ -72,4 +72,12 @@ struct sighook *atsigexit(sighook_fn *fn, void *arg);
  */
 void sigunhook(struct sighook *hook);
 
+/**
+ * Restore all signal handlers to their original dispositions (e.g. after fork()).
+ *
+ * @return
+ *         0 on success, -1 on failure.
+ */
+int sigreset(void);
+
 #endif // BFS_SIGHOOK_H