Subject: [PATCH v3 3/4] daemon: use sigaction() to install child_handler()

From: "Carlo Marcelo Arenas Belón via GitGitGadget" <[email-masked]>
Date: Thu, 26 Jun 2025 08:53:07 +0000

From: =?UTF-8?q?Carlo=20Marcelo=20Arenas=20Bel=C3=B3n?= <[email-masked]>

In a future change, the flags used for processing SIGCHLD will need to
be updated, which is only possible by using sigaction().

Replace signal() with an equivalent invocation of sigaction(), which
has the added benefit of using BSD semantics reliably and therefore
not needing the rearming call in the signal handler.

Signed-off-by: Carlo Marcelo Arenas Belón <[email-masked]>
---
 daemon.c | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/daemon.c b/daemon.c
index d1be61fd5789..155b2e180167 100644
--- a/daemon.c
+++ b/daemon.c
@@ -915,11 +915,9 @@ static void handle(int incoming, struct sockaddr *addr, socklen_t addrlen)
 static void child_handler(int signo UNUSED)
 {
 	/*
-	 * Otherwise empty handler because systemcalls will get interrupted
-	 * upon signal receipt
-	 * SysV needs the handler to be rearmed
+	 * Otherwise empty handler because systemcalls should get interrupted
+	 * upon signal receipt.
 	 */
-	signal(SIGCHLD, child_handler);
 }
 
 static int set_reuse_addr(int sockfd)
@@ -1120,6 +1118,7 @@ static void socksetup(struct string_list *listen_addr, int listen_port, struct s
 
 static int service_loop(struct socketlist *socklist)
 {
+	struct sigaction sa;
 	struct pollfd *pfd;
 
 	CALLOC_ARRAY(pfd, socklist->nr);
@@ -1129,7 +1128,10 @@ static int service_loop(struct socketlist *socklist)
 		pfd[i].events = POLLIN;
 	}
 
-	signal(SIGCHLD, child_handler);
+	sigemptyset(&sa.sa_mask);
+	sa.sa_flags = SA_NOCLDSTOP | SA_RESTART;
+	sa.sa_handler = child_handler;
+	sigaction(SIGCHLD, &sa, NULL);
 
 	for (;;) {
 		check_dead_children();
-- 
gitgitgadget