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pcm: Fallback open as the first instance for dmix & co

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dmix and other PCM plugins tries to open a secondary stream with
O_APPEND flag when the shmem was already attached by another.
However, when another streams have been already closed after the
shmem check, this open may return the error EBADFD, since the kernel
accepts O_APPEND only for the secondary streams.

This patch adds a workaround for such a case.  It just retries opening
the stream as the first instance (i.e. without O_APPEND flag).
This is basically safe behavior (the kernel takes care of races), even
we may do this even unconditionally.  But it's bad from the
performance POV, so we do it only when really needed.

Reported-by: Lars Lindqvist <lars.lindqvist@yandex.ru>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
This commit is contained in:
Takashi Iwai 2016-04-14 17:33:03 +02:00
parent e57b521c61
commit fdba9e1bad
3 changed files with 24 additions and 0 deletions
Download patch file Download diff file Expand all files Collapse all files

8
src/pcm/pcm_dmix.c
View file

@ -1020,6 +1020,7 @@ int snd_pcm_dmix_open(snd_pcm_t **pcmp, const char *name,
dmix->max_periods = opts->max_periods;
dmix->sync_ptr = snd_pcm_dmix_sync_ptr;
retry:
if (first_instance) {
/* recursion is already checked in
snd_pcm_direct_get_slave_ipc_offset() */
@ -1076,6 +1077,13 @@ int snd_pcm_dmix_open(snd_pcm_t **pcmp, const char *name,
SND_PCM_APPEND,
NULL);
if (ret < 0) {
/* all other streams have been closed;
* retry as the first instance
*/
if (ret == -EBADFD) {
first_instance = 1;
goto retry;
}
SNDERR("unable to open slave");
goto _err;
}

8
src/pcm/pcm_dshare.c
View file

@ -690,6 +690,7 @@ int snd_pcm_dshare_open(snd_pcm_t **pcmp, const char *name,
break;
}
retry:
first_instance = ret = snd_pcm_direct_shm_create_or_connect(dshare);
if (ret < 0) {
SNDERR("unable to create IPC shm instance");
@ -758,6 +759,13 @@ int snd_pcm_dshare_open(snd_pcm_t **pcmp, const char *name,
SND_PCM_APPEND,
NULL);
if (ret < 0) {
/* all other streams have been closed;
* retry as the first instance
*/
if (ret == -EBADFD) {
first_instance = 1;
goto retry;
}
SNDERR("unable to open slave");
goto _err;
}

8
src/pcm/pcm_dsnoop.c
View file

@ -583,6 +583,7 @@ int snd_pcm_dsnoop_open(snd_pcm_t **pcmp, const char *name,
break;
}
retry:
first_instance = ret = snd_pcm_direct_shm_create_or_connect(dsnoop);
if (ret < 0) {
SNDERR("unable to create IPC shm instance");
@ -651,6 +652,13 @@ int snd_pcm_dsnoop_open(snd_pcm_t **pcmp, const char *name,
SND_PCM_APPEND,
NULL);
if (ret < 0) {
/* all other streams have been closed;
* retry as the first instance
*/
if (ret == -EBADFD) {
first_instance = 1;
goto retry;
}
SNDERR("unable to open slave");
goto _err;
}