[CRIU] [PATCH] 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.

Signed-off-by: Ruslan Kuprieiev <kupruser at gmail.com>
---
 cr-service.c | 68 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++---
 1 file changed, 65 insertions(+), 3 deletions(-)

diff --git a/cr-service.c b/cr-service.c
index a79ebc7..f966036 100644
--- a/cr-service.c
+++ b/cr-service.c
@@ -19,6 +19,8 @@
 #include "pstree.h"
 #include "cr-service.h"
 
+#define MAX_WORKERS 16
+
 unsigned int service_sk_ino = -1;
 
 static int recv_criu_msg(int socket_fd, CriuReq **msg)
@@ -253,6 +255,46 @@ err:
 	return -1;
 }
 
+static void reap_worker(int signo)
+{
+	int saved_errno;
+	int status;
+	pid_t pid;
+
+	(void)signo;
+
+	saved_errno = errno;
+
+	errno = 0;
+	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);
+
+	errno = saved_errno;
+}
+
 int cr_service(bool daemon_mode)
 {
 	int server_fd = -1;
@@ -264,6 +306,9 @@ int cr_service(bool daemon_mode)
 	socklen_t server_addr_len;
 	socklen_t client_addr_len;
 
+	struct sigaction setup_action;
+	sigset_t block_mask;
+
 	server_fd = socket(AF_LOCAL, SOCK_SEQPACKET, 0);
 	if (server_fd == -1) {
 		pr_perror("Can't initialize service socket.");
@@ -299,7 +344,7 @@ int cr_service(bool daemon_mode)
 		goto err;
 	}
 
-	if (listen(server_fd, 16) == -1) {
+	if (listen(server_fd, MAX_WORKERS) == -1) {
 		pr_perror("Can't listen for socket connections.");
 		goto err;
 	}
@@ -323,16 +368,31 @@ int cr_service(bool daemon_mode)
 		}
 	}
 
-	/* FIXME Do not ignore children's return values */
-	signal(SIGCHLD, SIG_IGN);
+	/* Set SIGCHLD handler */
+	sigemptyset(&block_mask);
+
+	sigaddset(&block_mask, SIGCHLD);
+
+	/* FIXME May need to block some other signals too */
+	sigaddset(&block_mask, SIGINT);
+	sigaddset(&block_mask, SIGQUIT);
+
+	setup_action.sa_handler = reap_worker;
+	setup_action.sa_mask	= block_mask;
+	setup_action.sa_flags	= 0;
+
+	sigaction(SIGCHLD, &setup_action, NULL);
 
 	while (1) {
 		int sk;
 
 		pr_info("Waiting for connection...\n");
 
+		errno = 0;
 		sk = accept(server_fd, &client_addr, &client_addr_len);
 		if (sk == -1) {
+			if (errno == EINTR)
+				continue;
 			pr_perror("Can't accept connection.");
 			goto err;
 		}
@@ -340,6 +400,8 @@ int cr_service(bool daemon_mode)
 		pr_info("Connected.\n");
 		child_pid = fork();
 		if (child_pid == 0) {
+			/* Set default SIGCHLD handler back */
+			signal(SIGCHLD, SIG_DFL);
 			int ret;
 
 			close(server_fd);
-- 
1.8.1.2