[CRIU] [PATCH]v2 service: SIGCHLD handler

[Ruslan Kuprieiev]

Hi!

Now we're ignoring SIGCHLD from forked children.
This patch provides SIGCHLD handler, that will wait for child and write some
information about it's exit status to logfile.

P.S. This is my first signal handler, so please take a good look at this patch.

v2: fixed few mistakes. Thanks Andrew Vagin <avagin at parallels.com> for help.

Signed-off-by: Ruslan Kuprieiev <kupruser at gmail.com>
---
 cr-service.c | 77 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 75 insertions(+), 2 deletions(-)

diff --git a/cr-service.c b/cr-service.c
index a79ebc7..a920824 100644
--- a/cr-service.c
+++ b/cr-service.c
@@ -253,6 +253,53 @@ err:
 	return -1;
 }
 
+static void reap_worker(int signo)
+{
+	int saved_errno;
+	int status;
+	pid_t pid;
+
+	saved_errno = errno;
+
+	/*
+	 * Accordingly to signal(7):
+	 *   Multiple instances of real-time signals can be queued.  By
+	 *   contrast, if multiple instances of a standard signal are
+	 *   delivered while that signal is currently blocked, then only one
+	 *   instance is queued.
+	 * So, as we block SIGCHLD, lets wait for every child that has
+	 * changed state.
+	 */
+	while (1) {
+		pid = waitpid(-1, &status, WNOHANG|WUNTRACED|WCONTINUED);
+
+		if (pid <= 0) {
+			errno = saved_errno;
+			return;
+		}
+
+		if (WIFEXITED(status))
+			pr_info("Worker(pid %d) exited with %d\n",
+				pid, WEXITSTATUS(status));
+
+		else if (WIFSIGNALED(status)) {
+			pr_info("Worker(pid %d) ", pid);
+#ifdef WCOREDUMP
+			if (WCOREDUMP(status))
+				pr_info("prodused a core dump and ");
+#endif
+			pr_info("was killed by %d\n", WTERMSIG(status));
+
+		} else if (WIFSTOPPED(status))
+			pr_info("Worker(pid %d) was stopped by %d\n",
+				pid, WSTOPSIG(status));
+
+		else if (WIFCONTINUED(status))
+			pr_info("Worker(pid %d) was continued\n", pid);
+
+	}
+}
+
 int cr_service(bool daemon_mode)
 {
 	int server_fd = -1;
@@ -264,6 +311,9 @@ int cr_service(bool daemon_mode)
 	socklen_t server_addr_len;
 	socklen_t client_addr_len;
 
+	struct sigaction new_action, old_action;
+	sigset_t block_mask;
+
 	server_fd = socket(AF_LOCAL, SOCK_SEQPACKET, 0);
 	if (server_fd == -1) {
 		pr_perror("Can't initialize service socket.");
@@ -323,8 +373,25 @@ int cr_service(bool daemon_mode)
 		}
 	}
 
-	/* FIXME Do not ignore children's return values */
-	signal(SIGCHLD, SIG_IGN);
+	/* Set SIGCHLD handler */
+	sigemptyset(&block_mask);
+
+	/* FIXME May need to block some other signals too */
+	sigaddset(&block_mask, SIGCHLD);
+	sigaddset(&block_mask, SIGINT);
+	sigaddset(&block_mask, SIGQUIT);
+	sigaddset(&block_mask, SIGHUP);
+	sigaddset(&block_mask, SIGTERM);
+	sigaddset(&block_mask, SIGTSTP);
+
+	new_action.sa_handler = reap_worker;
+	new_action.sa_mask	= block_mask;
+	new_action.sa_flags	= SA_RESTART;
+
+	if (sigaction(SIGCHLD, &new_action, &old_action)) {
+		pr_perror("Can't setup SIGCHLD handler");
+		return -1;
+	}
 
 	while (1) {
 		int sk;
@@ -342,6 +409,12 @@ int cr_service(bool daemon_mode)
 		if (child_pid == 0) {
 			int ret;
 
+			/* Set default SIGCHLD handler back */
+			if (sigaction(SIGCHLD, &old_action, NULL)) {
+				pr_perror("Can't setup default SIGCHLD handler back");
+				exit(1);
+			}
+
 			close(server_fd);
 			ret = cr_service_work(sk);
 			close(sk);
-- 
1.8.1.2