1 files changed, 73 insertions, 20 deletions

diff --git a/cmd/zed/zed.c b/cmd/zed/zed.c
index c54a59b0a..bf29c0486 100644
--- a/cmd/zed/zed.c
+++ b/cmd/zed/zed.c
@@ -93,6 +93,9 @@ _setup_sig_handlers(void)
  * Lock all current and future pages in the virtual memory address space.
  *   Access to locked pages will never be delayed by a page fault.
  * EAGAIN is tested up to max_tries in case this is a transient error.
+ * Note that memory locks are not inherited by a child created via fork()
+ *   and are automatically removed during an execve().  As such, this must
+ *   be called after the daemon fork()s (when running in the background).
  */
 static void
 _lock_memory(void)
@@ -117,25 +120,57 @@ _lock_memory(void)
 }
 
 /*
- * Transform the process into a daemon.
+ * Start daemonization of the process including the double fork().
+ * The parent process will block here until _finish_daemonize() is called
+ *   (in the grandchild process), at which point the parent process will exit.
+ *   This prevents the parent process from exiting until initialization is
+ *   complete.
  */
 static void
-_become_daemon(void)
+_start_daemonize(void)
 {
 	pid_t pid;
-	int fd;
+	struct sigaction sa;
+
+	/* Create pipe for communicating with child during daemonization. */
+	zed_log_pipe_open();
 
+	/* Background process and ensure child is not process group leader. */
 	pid = fork();
 	if (pid < 0) {
 		zed_log_die("Failed to create child process: %s",
 		    strerror(errno));
 	} else if (pid > 0) {
+
+		/* Close writes since parent will only read from pipe. */
+		zed_log_pipe_close_writes();
+
+		/* Wait for notification that daemonization is complete. */
+		zed_log_pipe_wait();
+
+		zed_log_pipe_close_reads();
 		_exit(EXIT_SUCCESS);
 	}
+
+	/* Close reads since child will only write to pipe. */
+	zed_log_pipe_close_reads();
+
+	/* Create independent session and detach from terminal. */
 	if (setsid() < 0)
 		zed_log_die("Failed to create new session: %s",
 		    strerror(errno));
 
+	/* Prevent child from terminating on HUP when session leader exits. */
+	if (sigemptyset(&sa.sa_mask) < 0)
+		zed_log_die("Failed to initialize sigset");
+
+	sa.sa_flags = 0;
+	sa.sa_handler = SIG_IGN;
+
+	if (sigaction(SIGHUP, &sa, NULL) < 0)
+		zed_log_die("Failed to ignore SIGHUP");
+
+	/* Ensure process cannot re-acquire terminal. */
 	pid = fork();
 	if (pid < 0) {
 		zed_log_die("Failed to create grandchild process: %s",
@@ -143,25 +178,40 @@ _become_daemon(void)
 	} else if (pid > 0) {
 		_exit(EXIT_SUCCESS);
 	}
-	fd = open("/dev/null", O_RDWR);
+}
+
+/*
+ * Finish daemonization of the process by closing stdin/stdout/stderr.
+ * This must be called at the end of initialization after all external
+ *   communication channels are established and accessible.
+ */
+static void
+_finish_daemonize(void)
+{
+	int devnull;
 
-	if (fd < 0)
+	/* Preserve fd 0/1/2, but discard data to/from stdin/stdout/stderr. */
+	devnull = open("/dev/null", O_RDWR);
+	if (devnull < 0)
 		zed_log_die("Failed to open /dev/null: %s", strerror(errno));
 
-	if (dup2(fd, STDIN_FILENO) < 0)
+	if (dup2(devnull, STDIN_FILENO) < 0)
 		zed_log_die("Failed to dup /dev/null onto stdin: %s",
 		    strerror(errno));
 
-	if (dup2(fd, STDOUT_FILENO) < 0)
+	if (dup2(devnull, STDOUT_FILENO) < 0)
 		zed_log_die("Failed to dup /dev/null onto stdout: %s",
 		    strerror(errno));
 
-	if (dup2(fd, STDERR_FILENO) < 0)
+	if (dup2(devnull, STDERR_FILENO) < 0)
 		zed_log_die("Failed to dup /dev/null onto stderr: %s",
 		    strerror(errno));
 
-	if (close(fd) < 0)
+	if (close(devnull) < 0)
 		zed_log_die("Failed to close /dev/null: %s", strerror(errno));
+
+	/* Notify parent that daemonization is complete. */
+	zed_log_pipe_close_writes();
 }
 
 /*
@@ -184,33 +234,36 @@ main(int argc, char *argv[])
 	if (geteuid() != 0)
 		zed_log_die("Must be run as root");
 
-	(void) umask(0);
-
-	_setup_sig_handlers();
-
 	zed_conf_parse_file(zcp);
 
 	zed_file_close_from(STDERR_FILENO + 1);
 
+	(void) umask(0);
+
 	if (chdir("/") < 0)
 		zed_log_die("Failed to change to root directory");
 
 	if (zed_conf_scan_dir(zcp) < 0)
 		exit(EXIT_FAILURE);
 
-	if (zcp->do_memlock)
-		_lock_memory();
-
 	if (!zcp->do_foreground) {
-		_become_daemon();
+		_start_daemonize();
 		zed_log_syslog_open(LOG_DAEMON);
-		zed_log_stderr_close();
 	}
-	zed_log_msg(LOG_NOTICE,
-	    "ZFS Event Daemon %s-%s", ZFS_META_VERSION, ZFS_META_RELEASE);
+	_setup_sig_handlers();
+
+	if (zcp->do_memlock)
+		_lock_memory();
 
 	(void) zed_conf_write_pid(zcp);
 
+	if (!zcp->do_foreground)
+		_finish_daemonize();
+
+	zed_log_msg(LOG_NOTICE,
+	    "ZFS Event Daemon %s-%s (PID %d)",
+	    ZFS_META_VERSION, ZFS_META_RELEASE, (int) getpid());
+
 	if (zed_conf_open_state(zcp) < 0)
 		exit(EXIT_FAILURE);