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Fix semaphore deadlocks

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- Fixed unbalanced semaphores (which may cause deadlock)
- Do semaphore-up before blocking calls for communication with the server
- Don't discard semaphores on the client side
- Open slave PCMs always in non-blocking mode to avoid blocking by semaphore
  with the secondary open
This commit is contained in:
Takashi Iwai 2005-05-23 08:56:48 +00:00
parent ddd9c29a0d
commit a3ae02d884
4 changed files with 88 additions and 102 deletions
Download patch file Download diff file Expand all files Collapse all files

58
src/pcm/pcm_dsnoop.c
View file

@ -366,12 +366,8 @@ static int snd_pcm_dsnoop_close(snd_pcm_t *pcm)
snd_pcm_direct_server_discard(dsnoop);
if (dsnoop->client)
snd_pcm_direct_client_discard(dsnoop);
if (snd_pcm_direct_shm_discard(dsnoop) > 0) {
if (snd_pcm_direct_semaphore_discard(dsnoop) < 0)
snd_pcm_direct_semaphore_up(dsnoop, DIRECT_IPC_SEM_CLIENT);
} else {
snd_pcm_direct_semaphore_up(dsnoop, DIRECT_IPC_SEM_CLIENT);
}
snd_pcm_direct_shm_discard(dsnoop);
snd_pcm_direct_semaphore_up(dsnoop, DIRECT_IPC_SEM_CLIENT);
if (dsnoop->bindings)
free(dsnoop->bindings);
pcm->private_data = NULL;
@ -510,12 +506,12 @@ int snd_pcm_dsnoop_open(snd_pcm_t **pcmp, const char *name,
dsnoop = calloc(1, sizeof(snd_pcm_direct_t));
if (!dsnoop) {
ret = -ENOMEM;
goto _err;
goto _err_nosem;
}
ret = snd_pcm_direct_parse_bindings(dsnoop, bindings);
if (ret < 0)
goto _err;
goto _err_nosem;
dsnoop->ipc_key = ipc_key;
dsnoop->ipc_perm = ipc_perm;
@ -524,20 +520,20 @@ int snd_pcm_dsnoop_open(snd_pcm_t **pcmp, const char *name,
ret = snd_pcm_new(&pcm, dsnoop->type = SND_PCM_TYPE_DSNOOP, name, stream, mode);
if (ret < 0)
goto _err;
goto _err_nosem;
while (1) {
ret = snd_pcm_direct_semaphore_create_or_connect(dsnoop);
if (ret < 0) {
SNDERR("unable to create IPC semaphore");
goto _err;
goto _err_nosem;
}
ret = snd_pcm_direct_semaphore_down(dsnoop, DIRECT_IPC_SEM_CLIENT);
if (ret < 0) {
snd_pcm_direct_semaphore_discard(dsnoop);
if (--fail_sem_loop <= 0)
goto _err;
goto _err_nosem;
continue;
}
break;
@ -557,7 +553,7 @@ int snd_pcm_dsnoop_open(snd_pcm_t **pcmp, const char *name,
dsnoop->sync_ptr = snd_pcm_dsnoop_sync_ptr;
if (first_instance) {
ret = snd_pcm_open_slave(&spcm, root, sconf, stream, mode);
ret = snd_pcm_open_slave(&spcm, root, sconf, stream, mode | SND_PCM_NONBLOCK);
if (ret < 0) {
SNDERR("unable to open slave");
goto _err;
@ -584,12 +580,15 @@ int snd_pcm_dsnoop_open(snd_pcm_t **pcmp, const char *name,
dsnoop->shmptr->type = spcm->type;
} else {
/* up semaphore to avoid deadlock */
snd_pcm_direct_semaphore_up(dsnoop, DIRECT_IPC_SEM_CLIENT);
ret = snd_pcm_direct_client_connect(dsnoop);
if (ret < 0) {
SNDERR("unable to connect client");
return ret;
goto _err_nosem;
}
snd_pcm_direct_semaphore_down(dsnoop, DIRECT_IPC_SEM_CLIENT);
ret = snd_pcm_hw_open_fd(&spcm, "dsnoop_client", dsnoop->hw_fd, 0, 0);
if (ret < 0) {
SNDERR("unable to open hardware");
@ -634,25 +633,22 @@ int snd_pcm_dsnoop_open(snd_pcm_t **pcmp, const char *name,
return 0;
_err:
if (dsnoop->timer)
snd_timer_close(dsnoop->timer);
if (dsnoop->server)
snd_pcm_direct_server_discard(dsnoop);
if (dsnoop->client)
snd_pcm_direct_client_discard(dsnoop);
if (spcm)
snd_pcm_close(spcm);
if (dsnoop->shmid >= 0)
snd_pcm_direct_shm_discard(dsnoop);
if (snd_pcm_direct_semaphore_discard(dsnoop) < 0)
snd_pcm_direct_semaphore_up(dsnoop, DIRECT_IPC_SEM_CLIENT);
_err_nosem:
if (dsnoop) {
if (dsnoop->timer)
snd_timer_close(dsnoop->timer);
if (dsnoop->server)
snd_pcm_direct_server_discard(dsnoop);
if (dsnoop->client)
snd_pcm_direct_client_discard(dsnoop);
if (spcm)
snd_pcm_close(spcm);
if (dsnoop->shmid >= 0) {
if (snd_pcm_direct_shm_discard(dsnoop) > 0) {
if (dsnoop->semid >= 0) {
if (snd_pcm_direct_semaphore_discard(dsnoop) < 0)
snd_pcm_direct_semaphore_up(dsnoop, DIRECT_IPC_SEM_CLIENT);
}
}
}
if (dsnoop->bindings)
free(dsnoop->bindings);
if (dsnoop->bindings)
free(dsnoop->bindings);
free(dsnoop);
}
if (pcm)