do not exit mainloop when child is stopped

src/lxc/start.c

@@ -45,9 +45,31 @@
 #include <sys/un.h>
 #include <sys/poll.h>
 
-#ifdef HAVE_SYS_SIGNALFD_H 
+#ifdef HAVE_SYS_SIGNALFD_H
 #  include <sys/signalfd.h>
 #else
+/* assume kernel headers are too old */
+struct signalfd_siginfo
+{
+  uint32_t ssi_signo;
+  int32_t ssi_errno;
+  int32_t ssi_code;
+  uint32_t ssi_pid;
+  uint32_t ssi_uid;
+  int32_t ssi_fd;
+  uint32_t ssi_tid;
+  uint32_t ssi_band;
+  uint32_t ssi_overrun;
+  uint32_t ssi_trapno;
+  int32_t ssi_status;
+  int32_t ssi_int;
+  uint64_t ssi_ptr;
+  uint64_t ssi_utime;
+  uint64_t ssi_stime;
+  uint64_t ssi_addr;
+  uint8_t __pad[48];
+};
+
 #  ifndef __NR_signalfd4
 /* assume kernel headers are too old */
 #    if __i386__
@@ -198,11 +220,30 @@ static int setup_sigchld_fd(sigset_t *oldmask)
 	return fd;
 }
 
-static int sigchld_handler(int fd, void *data, 
+static int sigchld_handler(int fd, void *data,
 			   struct lxc_epoll_descr *descr)
 {
-	DEBUG("child exited");
+	struct signalfd_siginfo siginfo;
+	int ret;
+
+	ret = read(fd, &siginfo, sizeof(siginfo));
+	if (ret < 0) {
+		ERROR("failed to read sigchld info");
+		return -1;
+	}
+
+	if (ret != sizeof(siginfo)) {
+		ERROR("unexpected siginfo size");
+		return -1;
+	}
+
+	if (siginfo.ssi_code == CLD_STOPPED ||
+	    siginfo.ssi_code == CLD_CONTINUED) {
+		INFO("container init process was stopped/continued");
+		return 0;
+	}
 
+	DEBUG("container init process exited");
 	return 1;
 }