X-Git-Url: https://git.lttng.org/?p=lttng-tools.git;a=blobdiff_plain;f=src%2Fcommon%2Fdaemonize.cpp;fp=src%2Fcommon%2Fdaemonize.cpp;h=16af5a3f78ccec5da76033a48a7d0a04bd0c38f2;hp=0000000000000000000000000000000000000000;hb=a6bc4ca9d659caf016ef932fcd944029737ac57c;hpb=97535efaa975ca52bf02c2d5e76351bfd2e3defa

diff --git a/src/common/daemonize.cpp b/src/common/daemonize.cpp
new file mode 100644
index 000000000..16af5a3f7
--- /dev/null
+++ b/src/common/daemonize.cpp
@@ -0,0 +1,121 @@
+/*
+ * Copyright (C) 2013 David Goulet <dgoulet@efficios.com>
+ * Copyright (C) 2014 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
+ *
+ * SPDX-License-Identifier: GPL-2.0-only
+ *
+ */
+
+#define _LGPL_SOURCE
+#include <unistd.h>
+#include <common/compat/paths.h>
+#include <fcntl.h>
+#include <sys/wait.h>
+#include <stdlib.h>
+
+#include <urcu/system.h>
+
+#include <common/daemonize.h>
+#include <common/error.h>
+
+int lttng_daemonize(pid_t *child_ppid, int *completion_flag,
+		int close_fds)
+{
+	pid_t pid;
+
+	/* Get parent pid of this process. */
+	*child_ppid = getppid();
+
+	pid = fork();
+	if (pid < 0) {
+		PERROR("fork");
+		goto error;
+	} else if (pid == 0) {
+		int fd;
+		pid_t sid;
+		int ret;
+
+		/* Child */
+
+		/*
+		 * Get the newly created parent pid so we can signal
+		 * that process when we are ready to operate.
+		 */
+		*child_ppid = getppid();
+
+		sid = setsid();
+		if (sid < 0) {
+			PERROR("setsid");
+			goto error;
+		}
+
+		/*
+		 * Try to change directory to /. If we can't well at
+		 * least notify.
+		 */
+		ret = chdir("/");
+		if (ret < 0) {
+			PERROR("chdir");
+		}
+
+		if (close_fds) {
+			fd = open(_PATH_DEVNULL, O_RDWR, 0);
+			if (fd < 0) {
+				PERROR("open %s", _PATH_DEVNULL);
+				/*
+				 * Let 0, 1 and 2 open since we can't
+				 * bind them to /dev/null.
+				 */
+			} else {
+				(void) dup2(fd, STDIN_FILENO);
+				(void) dup2(fd, STDOUT_FILENO);
+				(void) dup2(fd, STDERR_FILENO);
+				if (fd > 2) {
+					ret = close(fd);
+					if (ret < 0) {
+						PERROR("close");
+					}
+				}
+			}
+		}
+		goto end;
+	} else {
+		/* Parent */
+
+		/*
+		 * Waiting for child to notify this parent that it can
+		 * exit. Note that sleep() is interrupted before the 1
+		 * second delay as soon as the signal is received, so it
+		 * will not cause visible delay for the user.
+		 */
+		while (!CMM_LOAD_SHARED(*completion_flag)) {
+			int status;
+			pid_t ret;
+
+			/*
+			 * Check if child exists without blocking. If
+			 * so, we have to stop this parent process and
+			 * return an error.
+			 */
+			ret = waitpid(pid, &status, WNOHANG);
+			if (ret < 0 || (ret != 0 && WIFEXITED(status))) {
+				/* The child exited somehow or was not valid. */
+				goto error;
+			}
+			sleep(1);
+		}
+
+		/*
+		 * From this point on, the parent can exit and the child
+		 * is now an operational session daemon ready to serve
+		 * clients and applications.
+		 */
+		exit(EXIT_SUCCESS);
+	}
+
+end:
+	return 0;
+
+error:
+	return -1;
+}