diff options
Diffstat (limited to 'client.c')
-rw-r--r-- | client.c | 53 |
1 files changed, 40 insertions, 13 deletions
@@ -39,6 +39,7 @@ int client_exitval; enum msgtype client_exittype; int client_attached; +int client_get_lock(char *); int client_connect(char *, int); void client_send_identify(int); void client_send_environ(void); @@ -49,13 +50,38 @@ void client_callback(int, short, void *); int client_dispatch_attached(void); int client_dispatch_wait(void *); +/* + * Get server create lock. If already held then server start is happening in + * another client, so block until the lock is released and return -1 to + * retry. Ignore other errors - just continue and start the server without the + * lock. + */ +int +client_get_lock(char *lockfile) +{ + int lockfd; + + if ((lockfd = open(lockfile, O_WRONLY|O_CREAT, 0600)) == -1) + fatal("open failed"); + + if (flock(lockfd, LOCK_EX|LOCK_NB) == -1 && errno == EWOULDBLOCK) { + while (flock(lockfd, LOCK_EX) == -1 && errno == EINTR) + /* nothing */; + close(lockfd); + return (-1); + } + + return (lockfd); +} + /* Connect client to server. */ int client_connect(char *path, int start_server) { struct sockaddr_un sa; size_t size; - int fd; + int fd, lockfd; + char *lockfile; memset(&sa, 0, sizeof sa); sa.sun_family = AF_UNIX; @@ -65,24 +91,25 @@ client_connect(char *path, int start_server) return (-1); } +retry: if ((fd = socket(AF_UNIX, SOCK_STREAM, 0)) == -1) fatal("socket failed"); if (connect(fd, (struct sockaddr *) &sa, SUN_LEN(&sa)) == -1) { - if (!start_server) + if (errno != ECONNREFUSED && errno != ENOENT) goto failed; - switch (errno) { - case ECONNREFUSED: - if (unlink(path) != 0) - goto failed; - /* FALLTHROUGH */ - case ENOENT: - if ((fd = server_start()) == -1) - goto failed; - break; - default: + if (!start_server) goto failed; - } + close(fd); + + xasprintf(&lockfile, "%s.lock", path); + if ((lockfd = client_get_lock(lockfile)) == -1) + goto retry; + if (unlink(path) != 0 && errno != ENOENT) + return (-1); + fd = server_start(lockfd, lockfile); + xfree(lockfile); + close(lockfd); } setblocking(fd, 0); |