add new switch --start to the PA binary which allows starting PA if it is not running yet. In contrast to normal startup an already running PA will not be considered an error. Also, take the autospawn lock so we can guarantee that after this call returns PA is ralive and running

git-svn-id: file:///home/lennart/svn/public/pulseaudio/trunk@2513 fefdeb5f-60dc-0310-8127-8f9354f1896f

man/pulseaudio.1.xml.in

@@ -33,6 +33,7 @@ USA.
     <cmd>pulseaudio <opt>--dump-modules</opt></cmd>
     <cmd>pulseaudio <opt>--dump-resample-methods</opt></cmd>
     <cmd>pulseaudio <opt>--cleanup-shm</opt></cmd>
+    <cmd>pulseaudio <opt>--start</opt></cmd>
     <cmd>pulseaudio <opt>--kill</opt></cmd>
     <cmd>pulseaudio <opt>--check</opt></cmd>
   </synopsis>
@@ -90,6 +91,16 @@ USA.
       (e.g. Linux).</p></optdesc>
     </option>
 
+    <option>
+      <p><opt>--start</opt></p>
+
+      <optdesc><p>Start PulseAudio if it is not running yet. This is
+      different from starting PulseAudio without <opt>--start</opt>
+      which would fail if PA is already running. PulseAudio is
+      guaranteed to be fully initialized when this call
+      returns. Implies <opt>--daemon</p>.</optdesc>
+    </option>
+
     <option>
       <p><opt>-k | --kill</opt></p>
 

src/daemon/cmdline.c

@@ -66,7 +66,8 @@ enum {
     ARG_DISABLE_SHM,
     ARG_DUMP_RESAMPLE_METHODS,
     ARG_SYSTEM,
-    ARG_CLEANUP_SHM
+    ARG_CLEANUP_SHM,
+    ARG_START
 };
 
 /* Tabel for getopt_long() */
@@ -91,6 +92,7 @@ static const struct option long_options[] = {
     {"dl-search-path",              1, 0, ARG_DL_SEARCH_PATH},
     {"resample-method",             1, 0, ARG_RESAMPLE_METHOD},
     {"kill",                        0, 0, ARG_KILL},
+    {"start",                       0, 0, ARG_START},
     {"use-pid-file",                2, 0, ARG_USE_PID_FILE},
     {"check",                       0, 0, ARG_CHECK},
     {"system",                      2, 0, ARG_SYSTEM},
@@ -119,6 +121,7 @@ void pa_cmdline_help(const char *argv0) {
            "      --dump-modules                    Dump list of available modules\n"
            "      --dump-resample-methods           Dump available resample methods\n"
            "      --cleanup-shm                     Cleanup stale shared memory segments\n"
+           "      --start                           Start the daemon if it is not running\n"
            "  -k  --kill                            Kill a running daemon\n"
            "      --check                           Check for a running daemon\n\n"
 
@@ -207,6 +210,11 @@ int pa_cmdline_parse(pa_daemon_conf *conf, int argc, char *const argv [], int *d
                 conf->cmd = PA_CMD_KILL;
                 break;
 
+            case ARG_START:
+                conf->cmd = PA_CMD_START;
+                conf->daemonize = TRUE;
+                break;
+
             case ARG_CHECK:
                 conf->cmd = PA_CMD_CHECK;
                 break;

src/daemon/daemon-conf.h

@@ -37,6 +37,7 @@
 /* The actual command to execute */
 typedef enum pa_daemon_conf_cmd {
     PA_CMD_DAEMON,  /* the default */
+    PA_CMD_START,
     PA_CMD_HELP,
     PA_CMD_VERSION,
     PA_CMD_DUMP_CONF,

src/daemon/main.c

@@ -96,6 +96,8 @@
 #include "ltdl-bind-now.h"
 #include "polkit.h"
 
+#define AUTOSPAWN_LOCK "autospawn.lock"
+
 #ifdef HAVE_LIBWRAP
 /* Only one instance of these variables */
 int allow_severity = LOG_INFO;
@@ -344,6 +346,8 @@ int main(int argc, char *argv[]) {
     pa_time_event *win32_timer;
     struct timeval win32_tv;
 #endif
+    char *lf = NULL;
+    int autospawn_lock_fd = -1;
 
 #if defined(__linux__) && defined(__OPTIMIZE__)
     /*
@@ -486,13 +490,13 @@ int main(int argc, char *argv[]) {
     if (conf->high_priority && !pa_can_high_priority())
         pa_log_warn("High-priority scheduling enabled in configuration but not allowed by policy.");
 
-    if (conf->high_priority && conf->cmd == PA_CMD_DAEMON)
+    if (conf->high_priority && (conf->cmd == PA_CMD_DAEMON || conf->cmd == PA_CMD_START))
         pa_raise_priority(conf->nice_level);
 
     if (suid_root) {
         pa_bool_t drop;
 
-        drop = conf->cmd != PA_CMD_DAEMON || !conf->realtime_scheduling;
+        drop = (conf->cmd != PA_CMD_DAEMON && conf->cmd != PA_CMD_START) || !conf->realtime_scheduling;
 
 #ifdef RLIMIT_RTPRIO
         if (!drop) {
@@ -608,7 +612,7 @@ int main(int argc, char *argv[]) {
             goto finish;
 
         default:
-            pa_assert(conf->cmd == PA_CMD_DAEMON);
+            pa_assert(conf->cmd == PA_CMD_DAEMON || conf->cmd == PA_CMD_START);
     }
 
     if (real_root && !conf->system_instance)
@@ -618,6 +622,15 @@ int main(int argc, char *argv[]) {
         goto finish;
     }
 
+    if (conf->cmd == PA_CMD_START) {
+        /* If we shall start PA only when it is not running yet, we
+         * first take the autospawn lock to make things
+         * synchronous. */
+
+        lf = pa_runtime_path(AUTOSPAWN_LOCK);
+        autospawn_lock_fd = pa_lock_lockfile(lf);
+    }
+
     if (conf->daemonize) {
         pid_t child;
         int tty_fd;
@@ -661,6 +674,14 @@ int main(int argc, char *argv[]) {
             goto finish;
         }
 
+        if (autospawn_lock_fd >= 0) {
+            /* The lock file is unlocked from the parent, so we need
+             * to close it in the child */
+
+            pa_close(autospawn_lock_fd);
+            autospawn_lock_fd = -1;
+        }
+
         pa_assert_se(pa_close(daemon_pipe[0]) == 0);
         daemon_pipe[0] = -1;
 #endif
@@ -728,7 +749,20 @@ int main(int argc, char *argv[]) {
     pa_log_info("Running in system mode: %s", pa_yes_no(pa_in_system_mode()));
 
     if (conf->use_pid_file) {
-        if (pa_pid_file_create("pulseaudio") < 0) {
+        int z;
+
+        if ((z = pa_pid_file_create("pulseaudio")) != 0) {
+
+            if (conf->cmd == PA_CMD_START && z > 0) {
+                /* If we are already running and with are run in
+                 * --start mode, then let's return this as success. */
+
+                pa_log_info("z=%i rock!", z);
+
+                retval = 0;
+                goto finish;
+            }
+
             pa_log("pa_pid_file_create() failed.");
             goto finish;
         }
@@ -826,11 +860,12 @@ int main(int argc, char *argv[]) {
         goto finish;
     }
 
-
 #ifdef HAVE_FORK
-    if (conf->daemonize) {
+    if (daemon_pipe[1] >= 0) {
         int ok = 0;
         pa_loop_write(daemon_pipe[1], &ok, sizeof(ok), NULL);
+        pa_close(daemon_pipe[1]);
+        daemon_pipe[1] = -1;
     }
 #endif
 
@@ -844,6 +879,12 @@ int main(int argc, char *argv[]) {
 
 finish:
 
+    if (autospawn_lock_fd >= 0)
+        pa_unlock_lockfile(lf, autospawn_lock_fd);
+
+    if (lf)
+        pa_xfree(lf);
+
 #ifdef OS_IS_WIN32
     if (win32_timer)
         pa_mainloop_get_api(mainloop)->time_free(win32_timer);
@@ -860,6 +901,9 @@ finish:
     pa_signal_done();
 
 #ifdef HAVE_FORK
+    if (daemon_pipe[1] >= 0)
+        pa_loop_write(daemon_pipe[1], &retval, sizeof(retval), NULL);
+
     pa_close_pipe(daemon_pipe);
 #endif
 

src/pulsecore/pid.c

@@ -220,6 +220,7 @@ int pa_pid_file_create(const char *procname) {
 
             if (ours) {
                 pa_log("Daemon already running.");
+                ret = 1;
                 goto fail;
             }
         }