lockf is entirely useless and it was a mistake to change to it, go back

to using flock which actually works sensibly. Also always retry the lock
to fix a potential race, and add some extra logging.

diff --git a/usr.bin/tmux/client.c b/usr.bin/tmux/client.c
index ce2d68e..10d2d20 100644 (file)
--- a/usr.bin/tmux/client.c
+++ b/usr.bin/tmux/client.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: client.c,v 1.81 2014/07/13 20:51:08 krw Exp $ */
+/* $OpenBSD: client.c,v 1.82 2014/07/21 10:52:48 nicm Exp $ */
 
 /*
  * Copyright (c) 2007 Nicholas Marriott <nicm@users.sourceforge.net>
@@ -77,13 +77,18 @@ client_get_lock(char *lockfile)
 
        if ((lockfd = open(lockfile, O_WRONLY|O_CREAT, 0600)) == -1)
                fatal("open failed");
+       log_debug("lock file is %s", lockfile);
 
-       if (lockf(lockfd, F_TLOCK, 0) == -1 && errno == EAGAIN) {
-               while (lockf(lockfd, F_LOCK, 0) == -1 && errno == EINTR)
+       if (flock(lockfd, LOCK_EX|LOCK_NB) == -1) {
+               log_debug("flock failed: %s", strerror(errno));
+               if (errno != EAGAIN)
+                       return (lockfd);
+               while (flock(lockfd, LOCK_EX) == -1 && errno == EINTR)
                        /* nothing */;
                close(lockfd);
                return (-1);
        }
+       log_debug("flock succeeded");
 
        return (lockfd);
 }
@@ -94,8 +99,8 @@ client_connect(char *path, int start_server)
 {
        struct sockaddr_un      sa;
        size_t                  size;
-       int                     fd, lockfd;
-       char                   *lockfile;
+       int                     fd, lockfd = -1, locked = 0;
+       char                   *lockfile = NULL;
 
        memset(&sa, 0, sizeof sa);
        sa.sun_family = AF_UNIX;
@@ -104,29 +109,48 @@ client_connect(char *path, int start_server)
                errno = ENAMETOOLONG;
                return (-1);
        }
+       log_debug("socket is %s", path);
 
 retry:
        if ((fd = socket(AF_UNIX, SOCK_STREAM, 0)) == -1)
                fatal("socket failed");
 
+       log_debug("trying connect");
        if (connect(fd, (struct sockaddr *) &sa, SUN_LEN(&sa)) == -1) {
+               log_debug("connect failed: %s", strerror(errno));
                if (errno != ECONNREFUSED && errno != ENOENT)
                        goto failed;
                if (!start_server)
                        goto failed;
                close(fd);
 
-               xasprintf(&lockfile, "%s.lock", path);
-               if ((lockfd = client_get_lock(lockfile)) == -1) {
-                       free(lockfile);
+               if (!locked) {
+                       xasprintf(&lockfile, "%s.lock", path);
+                       if ((lockfd = client_get_lock(lockfile)) == -1) {
+                               log_debug("didn't get lock");
+                               free(lockfile);
+                               goto retry;
+                       }
+                       log_debug("got lock");
+
+                       /*
+                        * Always retry at least once, even if we got the lock,
+                        * because another client could have taken the lock,
+                        * started the server and released the lock between our
+                        * connect() and flock().
+                        */
+                       locked = 1;
                        goto retry;
                }
+
                if (unlink(path) != 0 && errno != ENOENT) {
                        free(lockfile);
                        close(lockfd);
                        return (-1);
                }
                fd = server_start(lockfd, lockfile);
+       }
+       if (locked) {
                free(lockfile);
                close(lockfd);
        }
@@ -233,7 +257,11 @@ client_main(int argc, char **argv, int flags)
                return (1);
        }
 
-       /* Initialise the client socket and start the server. */
+       /* Set process title, log and signals now this is the client. */
+       setproctitle("client (%s)", socket_path);
+       logfile("client");
+
+       /* Initialize the client socket and start the server. */
        fd = client_connect(socket_path, cmdflags & CMD_STARTSERVER);
        if (fd == -1) {
                fprintf(stderr, "failed to connect to server: %s\n",
@@ -241,10 +269,6 @@ client_main(int argc, char **argv, int flags)
                return (1);
        }
 
-       /* Set process title, log and signals now this is the client. */
-       setproctitle("client (%s)", socket_path);
-       logfile("client");
-
        /* Create imsg. */
        imsg_init(&client_ibuf, fd);
        event_set(&client_event, fd, EV_READ, client_callback, shell_cmd);

diff --git a/usr.bin/tmux/server.c b/usr.bin/tmux/server.c
index f3706ae..3289dc2 100644 (file)
--- a/usr.bin/tmux/server.c
+++ b/usr.bin/tmux/server.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: server.c,v 1.114 2014/05/14 06:21:19 nicm Exp $ */
+/* $OpenBSD: server.c,v 1.115 2014/07/21 10:52:48 nicm Exp $ */
 
 /*
  * Copyright (c) 2007 Nicholas Marriott <nicm@users.sourceforge.net>
@@ -111,6 +111,7 @@ server_start(int lockfd, char *lockfile)
        /* The first client is special and gets a socketpair; create it. */
        if (socketpair(AF_UNIX, SOCK_STREAM, PF_UNSPEC, pair) != 0)
                fatal("socketpair failed");
+       log_debug("starting server");
 
        switch (fork()) {
        case -1: