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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

8
src/pcm/pcm_direct.c
View file

@ -76,10 +76,8 @@ int snd_pcm_direct_semaphore_discard(snd_pcm_direct_t *dmix)
int snd_pcm_direct_semaphore_down(snd_pcm_direct_t *dmix, int sem_num)
{
struct sembuf op[2] = { { 0, 0, SEM_UNDO }, { 0, 1, SEM_UNDO | IPC_NOWAIT } };
struct sembuf op[2] = { { sem_num, 0, 0 }, { sem_num, 1, SEM_UNDO } };
assert(dmix->semid >= 0);
op[0].sem_num = sem_num;
op[1].sem_num = sem_num;
if (semop(dmix->semid, op, 2) < 0)
return -errno;
return 0;
@ -87,9 +85,8 @@ int snd_pcm_direct_semaphore_down(snd_pcm_direct_t *dmix, int sem_num)
int snd_pcm_direct_semaphore_up(snd_pcm_direct_t *dmix, int sem_num)
{
struct sembuf op = { 0, -1, SEM_UNDO | IPC_NOWAIT };
struct sembuf op = { sem_num, -1, SEM_UNDO | IPC_NOWAIT };
assert(dmix->semid >= 0);
op.sem_num = sem_num;
if (semop(dmix->semid, &op, 1) < 0)
return -errno;
return 0;
@ -252,6 +249,7 @@ static void server_job(snd_pcm_direct_t *dmix)
snd_pcm_direct_semaphore_down(dmix, DIRECT_IPC_SEM_CLIENT);
if (shmctl(dmix->shmid, IPC_STAT, &buf) < 0) {
snd_pcm_direct_shm_discard(dmix);
snd_pcm_direct_semaphore_up(dmix, DIRECT_IPC_SEM_CLIENT);
continue;
}
server_printf("DIRECT SERVER: nattch = %i\n", (int)buf.shm_nattch);

32
src/pcm/pcm_dmix.c
View file

@ -585,12 +585,8 @@ static int snd_pcm_dmix_close(snd_pcm_t *pcm)
if (dmix->client)
snd_pcm_direct_client_discard(dmix);
shm_sum_discard(dmix);
if (snd_pcm_direct_shm_discard(dmix) > 0) {
if (snd_pcm_direct_semaphore_discard(dmix) < 0)
snd_pcm_direct_shm_discard(dmix);
snd_pcm_direct_semaphore_up(dmix, DIRECT_IPC_SEM_CLIENT);
} else {
snd_pcm_direct_semaphore_up(dmix, DIRECT_IPC_SEM_CLIENT);
}
if (dmix->bindings)
free(dmix->bindings);
pcm->private_data = NULL;
@ -748,12 +744,12 @@ int snd_pcm_dmix_open(snd_pcm_t **pcmp, const char *name,
dmix = calloc(1, sizeof(snd_pcm_direct_t));
if (!dmix) {
ret = -ENOMEM;
goto _err;
goto _err_nosem;
}
ret = snd_pcm_direct_parse_bindings(dmix, bindings);
if (ret < 0)
goto _err;
goto _err_nosem;
dmix->ipc_key = ipc_key;
dmix->ipc_perm = ipc_perm;
@ -769,13 +765,13 @@ int snd_pcm_dmix_open(snd_pcm_t **pcmp, const char *name,
ret = snd_pcm_direct_semaphore_create_or_connect(dmix);
if (ret < 0) {
SNDERR("unable to create IPC semaphore");
goto _err;
goto _err_nosem;
}
ret = snd_pcm_direct_semaphore_down(dmix, DIRECT_IPC_SEM_CLIENT);
if (ret < 0) {
snd_pcm_direct_semaphore_discard(dmix);
if (--fail_sem_loop <= 0)
goto _err;
goto _err_nosem;
continue;
}
break;
@ -795,7 +791,7 @@ int snd_pcm_dmix_open(snd_pcm_t **pcmp, const char *name,
dmix->sync_ptr = snd_pcm_dmix_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;
@ -825,12 +821,15 @@ int snd_pcm_dmix_open(snd_pcm_t **pcmp, const char *name,
dmix->shmptr->type = spcm->type;
} else {
/* up semaphore to avoid deadlock */
snd_pcm_direct_semaphore_up(dmix, DIRECT_IPC_SEM_CLIENT);
ret = snd_pcm_direct_client_connect(dmix);
if (ret < 0) {
SNDERR("unable to connect client");
return ret;
goto _err_nosem;
}
snd_pcm_direct_semaphore_down(dmix, DIRECT_IPC_SEM_CLIENT);
ret = snd_pcm_hw_open_fd(&spcm, "dmix_client", dmix->hw_fd, 0, 0);
if (ret < 0) {
SNDERR("unable to open hardware");
@ -883,7 +882,6 @@ int snd_pcm_dmix_open(snd_pcm_t **pcmp, const char *name,
return 0;
_err:
if (dmix) {
if (dmix->timer)
snd_timer_close(dmix->timer);
if (dmix->server)
@ -894,14 +892,12 @@ int snd_pcm_dmix_open(snd_pcm_t **pcmp, const char *name,
snd_pcm_close(spcm);
if (dmix->u.dmix.shmid_sum >= 0)
shm_sum_discard(dmix);
if (dmix->shmid >= 0) {
if (snd_pcm_direct_shm_discard(dmix) > 0) {
if (dmix->semid >= 0) {
if (dmix->shmid >= 0)
snd_pcm_direct_shm_discard(dmix);
if (snd_pcm_direct_semaphore_discard(dmix) < 0)
snd_pcm_direct_semaphore_up(dmix, DIRECT_IPC_SEM_CLIENT);
}
}
}
_err_nosem:
if (dmix) {
if (dmix->bindings)
free(dmix->bindings);
free(dmix);

36
src/pcm/pcm_dshare.c
View file

@ -459,12 +459,8 @@ static int snd_pcm_dshare_close(snd_pcm_t *pcm)
snd_pcm_direct_server_discard(dshare);
if (dshare->client)
snd_pcm_direct_client_discard(dshare);
if (snd_pcm_direct_shm_discard(dshare) > 0) {
if (snd_pcm_direct_semaphore_discard(dshare) < 0)
snd_pcm_direct_shm_discard(dshare);
snd_pcm_direct_semaphore_up(dshare, DIRECT_IPC_SEM_CLIENT);
} else {
snd_pcm_direct_semaphore_up(dshare, DIRECT_IPC_SEM_CLIENT);
}
if (dshare->bindings)
free(dshare->bindings);
pcm->private_data = NULL;
@ -614,17 +610,17 @@ int snd_pcm_dshare_open(snd_pcm_t **pcmp, const char *name,
dshare = calloc(1, sizeof(snd_pcm_direct_t));
if (!dshare) {
ret = -ENOMEM;
goto _err;
goto _err_nosem;
}
ret = snd_pcm_direct_parse_bindings(dshare, bindings);
if (ret < 0)
goto _err;
goto _err_nosem;
if (!dshare->bindings) {
SNDERR("dshare: specify bindings!!!");
ret = -EINVAL;
goto _err;
goto _err_nosem;
}
dshare->ipc_key = ipc_key;
@ -634,20 +630,20 @@ int snd_pcm_dshare_open(snd_pcm_t **pcmp, const char *name,
ret = snd_pcm_new(&pcm, dshare->type = SND_PCM_TYPE_DSHARE, name, stream, mode);
if (ret < 0)
goto _err;
goto _err_nosem;
while (1) {
ret = snd_pcm_direct_semaphore_create_or_connect(dshare);
if (ret < 0) {
SNDERR("unable to create IPC semaphore");
goto _err;
goto _err_nosem;
}
ret = snd_pcm_direct_semaphore_down(dshare, DIRECT_IPC_SEM_CLIENT);
if (ret < 0) {
snd_pcm_direct_semaphore_discard(dshare);
if (--fail_sem_loop <= 0)
goto _err;
goto _err_nosem;
continue;
}
break;
@ -667,7 +663,7 @@ int snd_pcm_dshare_open(snd_pcm_t **pcmp, const char *name,
dshare->sync_ptr = snd_pcm_dshare_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;
@ -694,12 +690,15 @@ int snd_pcm_dshare_open(snd_pcm_t **pcmp, const char *name,
dshare->shmptr->type = spcm->type;
} else {
/* up semaphore to avoid deadlock */
snd_pcm_direct_semaphore_up(dshare, DIRECT_IPC_SEM_CLIENT);
ret = snd_pcm_direct_client_connect(dshare);
if (ret < 0) {
SNDERR("unable to connect client");
return ret;
goto _err_nosem;
}
snd_pcm_direct_semaphore_down(dshare, DIRECT_IPC_SEM_CLIENT);
ret = snd_pcm_hw_open_fd(&spcm, "dshare_client", dshare->hw_fd, 0, 0);
if (ret < 0) {
SNDERR("unable to open hardware");
@ -751,7 +750,6 @@ int snd_pcm_dshare_open(snd_pcm_t **pcmp, const char *name,
return 0;
_err:
if (dshare) {
if (dshare->shmptr)
dshare->shmptr->u.dshare.chn_mask &= ~dshare->u.dshare.chn_mask;
if (dshare->timer)
@ -762,14 +760,12 @@ int snd_pcm_dshare_open(snd_pcm_t **pcmp, const char *name,
snd_pcm_direct_client_discard(dshare);
if (spcm)
snd_pcm_close(spcm);
if (dshare->shmid >= 0) {
if (snd_pcm_direct_shm_discard(dshare) > 0) {
if (dshare->semid >= 0) {
if (dshare->shmid >= 0)
snd_pcm_direct_shm_discard(dshare);
if (snd_pcm_direct_semaphore_discard(dshare) < 0)
snd_pcm_direct_semaphore_up(dshare, DIRECT_IPC_SEM_CLIENT);
}
}
}
_err_nosem:
if (dshare) {
if (dshare->bindings)
free(dshare->bindings);
free(dshare);

34
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_shm_discard(dsnoop);
snd_pcm_direct_semaphore_up(dsnoop, DIRECT_IPC_SEM_CLIENT);
} else {
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");
@ -634,7 +633,6 @@ int snd_pcm_dsnoop_open(snd_pcm_t **pcmp, const char *name,
return 0;
_err:
if (dsnoop) {
if (dsnoop->timer)
snd_timer_close(dsnoop->timer);
if (dsnoop->server)
@ -643,14 +641,12 @@ int snd_pcm_dsnoop_open(snd_pcm_t **pcmp, const char *name,
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 (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->bindings)
free(dsnoop->bindings);
free(dsnoop);