[PATCH] alsactl: Skip restore during the lock

[Takashi Iwai]

Currently alsactl-restore tries to initialize the device when an error
is found for restore action.  But this isn't the right behavior in the
case where the lock is held; it implies that another alsactl is
running concurrently, hence you shouldn't initialize the card at the
same time.  The situation is found easily when two alsactls get
started by both udev and systemd (note that those two invocations are
the designed behavior, see /usr/lib/udev/rules.d/78-sound-cards.rules
for details).

This patch changes load_state() not to handle the initialization if
the locking fails.

BugLink: https://bugzilla.opensuse.org/show_bug.cgi?id=1179904
Signed-off-by: Takashi Iwai <tiwai at suse.de>
---
 alsactl/state.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/alsactl/state.c b/alsactl/state.c
index ea1d3bcaaddf..8d1d814341bd 100644
--- a/alsactl/state.c
+++ b/alsactl/state.c
@@ -1663,7 +1663,12 @@ int load_state(const char *file, const char *initfile, int initflags,
 		err = snd_input_stdio_attach(&in, stdin, 0);
 	} else {
 		lock_fd = state_lock(file, 10);
-		err = lock_fd >= 0 ? snd_input_stdio_open(&in, file, "r") : lock_fd;
+		/* skip restore if already locked; i.e. concurrent accesses */
+		if (lock_fd < 0) {
+			err = 0;
+			goto out_global;
+		}
+		err = snd_input_stdio_open(&in, file, "r");
 	}
 	if (err >= 0) {
 		err = snd_config_load(config, in);
@@ -1781,6 +1786,7 @@ single:
 	err = finalerr;
 out:
 	snd_config_delete(config);
+out_global:
 	snd_config_update_free_global();
 	return err;
 }
-- 
2.26.2