Merge branch 'cb/daemon-reap-children'

Futz with SIGCHLD handling in "git daemon".

* cb/daemon-reap-children:
  daemon: use sigaction() to install child_handler()
  compat/mingw: allow sigaction(SIGCHLD)

Author: gitster

compat/mingw-posix.h

@@ -96,6 +96,7 @@ struct sigaction {
 	unsigned sa_flags;
 };
 #define SA_RESTART 0
+#define SA_NOCLDSTOP 1
 
 struct itimerval {
 	struct timeval it_value, it_interval;

compat/mingw.c

@@ -2561,7 +2561,9 @@ int setitimer(int type UNUSED, struct itimerval *in, struct itimerval *out)
 
 int sigaction(int sig, struct sigaction *in, struct sigaction *out)
 {
-	if (sig != SIGALRM)
+	if (sig == SIGCHLD)
+		return -1;
+	else if (sig != SIGALRM)
 		return errno = EINVAL,
 			error("sigaction only implemented for SIGALRM");
 	if (out)

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)
@@ -1115,6 +1113,7 @@ 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);
@@ -1124,7 +1123,10 @@ 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.sa_handler = child_handler;
+	sigaction(SIGCHLD, &sa, NULL);
 
 	for (;;) {
 		check_dead_children();