X-Git-Url: http://git.onelab.eu/?a=blobdiff_plain;f=lib%2Fdaemon.c;h=484919622b11e03a7678763a6f9ebe9d79db44fb;hb=85b20fd6ee585f462e012fbcc7f966a81edab2ed;hp=84ed6147169e6bddf57cda35f28cd591c2046ee3;hpb=e368cad8ecf6dbf272b2a3775b2e3e5e2dc6a5cf;p=sliver-openvswitch.git

diff --git a/lib/daemon.c b/lib/daemon.c
index 84ed61471..484919622 100644
--- a/lib/daemon.c
+++ b/lib/daemon.c
@@ -175,57 +175,63 @@ make_pidfile(void)
     int error;
 
     /* Create a temporary pidfile. */
-    tmpfile = xasprintf("%s.tmp%ld", pidfile, pid);
-    fatal_signal_add_file_to_unlink(tmpfile);
-    file = fopen(tmpfile, "w+");
+    if (overwrite_pidfile) {
+        tmpfile = xasprintf("%s.tmp%ld", pidfile, pid);
+        fatal_signal_add_file_to_unlink(tmpfile);
+    } else {
+        /* Everyone shares the same file which will be treated as a lock.  To
+         * avoid some uncomfortable race conditions, we can't set up the fatal
+         * signal unlink until we've acquired it. */
+        tmpfile = xasprintf("%s.tmp", pidfile);
+    }
+
+    file = fopen(tmpfile, "a+");
     if (!file) {
         VLOG_FATAL("%s: create failed (%s)", tmpfile, strerror(errno));
     }
 
+    error = lock_pidfile(file, F_SETLK);
+    if (error) {
+        /* Looks like we failed to acquire the lock.  Note that, if we failed
+         * for some other reason (and '!overwrite_pidfile'), we will have
+         * left 'tmpfile' as garbage in the file system. */
+        VLOG_FATAL("%s: fcntl(F_SETLK) failed (%s)", tmpfile, strerror(error));
+    }
+
+    if (!overwrite_pidfile) {
+        /* We acquired the lock.  Make sure to clean up on exit, and verify
+         * that we're allowed to create the actual pidfile. */
+        fatal_signal_add_file_to_unlink(tmpfile);
+        check_already_running();
+    }
+
     if (fstat(fileno(file), &s) == -1) {
         VLOG_FATAL("%s: fstat failed (%s)", tmpfile, strerror(errno));
     }
 
+    if (ftruncate(fileno(file), 0) == -1) {
+        VLOG_FATAL("%s: truncate failed (%s)", tmpfile, strerror(errno));
+    }
+
     fprintf(file, "%ld\n", pid);
     if (fflush(file) == EOF) {
         VLOG_FATAL("%s: write failed (%s)", tmpfile, strerror(errno));
     }
 
-    error = lock_pidfile(file, F_SETLK);
-    if (error) {
-        VLOG_FATAL("%s: fcntl(F_SETLK) failed (%s)", tmpfile, strerror(error));
-    }
+    error = rename(tmpfile, pidfile);
 
-    /* Rename or link it to the correct name. */
-    if (overwrite_pidfile) {
-        if (rename(tmpfile, pidfile) < 0) {
-            VLOG_FATAL("failed to rename \"%s\" to \"%s\" (%s)",
-                       tmpfile, pidfile, strerror(errno));
-        }
-    } else {
-        do {
-            error = link(tmpfile, pidfile) == -1 ? errno : 0;
-            if (error == EEXIST) {
-                check_already_running();
-            }
-        } while (error == EINTR || error == EEXIST);
-        if (error) {
-            VLOG_FATAL("failed to link \"%s\" as \"%s\" (%s)",
-                       tmpfile, pidfile, strerror(error));
-        }
+    /* Due to a race, 'tmpfile' may be owned by a different process, so we
+     * shouldn't delete it on exit. */
+    fatal_signal_remove_file_to_unlink(tmpfile);
+
+    if (error < 0) {
+        VLOG_FATAL("failed to rename \"%s\" to \"%s\" (%s)",
+                   tmpfile, pidfile, strerror(errno));
     }
 
     /* Ensure that the pidfile will get deleted on exit. */
     fatal_signal_add_file_to_unlink(pidfile);
 
-    /* Delete the temporary pidfile if it still exists. */
-    if (!overwrite_pidfile) {
-        error = fatal_signal_unlink_file_now(tmpfile);
-        if (error) {
-            VLOG_FATAL("%s: unlink failed (%s)", tmpfile, strerror(error));
-        }
-    }
-
     /* Clean up.
      *
      * We don't close 'file' because its file descriptor must remain open to
@@ -385,9 +391,8 @@ monitor_daemon(pid_t daemon_pid)
         int retval;
         int status;
 
-        proctitle_set("%s: monitoring pid %lu (%s)",
-                      program_name, (unsigned long int) daemon_pid,
-                      status_msg);
+        proctitle_set("monitoring pid %lu (%s)",
+                      (unsigned long int) daemon_pid, status_msg);
 
         do {
             retval = waitpid(daemon_pid, &status, 0);
@@ -487,7 +492,9 @@ daemonize_start(void)
             /* Running in parent process. */
             exit(0);
         }
+
         /* Running in daemon or monitor process. */
+        setsid();
     }
 
     if (monitor) {
@@ -541,7 +548,6 @@ void
 daemonize_post_detach(void)
 {
     if (detach) {
-        setsid();
         if (chdir_) {
             ignore(chdir("/"));
         }