On Mon, 22 Aug 2016 18:04:33 +0200,
Ismael Luceno wrote:
>
> Easily seen when two threads try at the same time, one of them will fail.
>
> The bug was identified by using apulse with Skype.
>
> Fixes: dec428c35221 ("pcm: fix 'unable to create IPC shm instance' caused by fork from a thread")
> Fixes: https://github.com/i-rinat/apulse/issues/38
> Signed-off-by: Ismael Luceno <ismael@xxxxxxxxxxx>
OK, I'll apply this one, as this change alone is fine.
But in general, this implies that the application hitting this is
buggy. You can't reliably call snd_pcm_open() for the same PCM stream
concurrently via multi threads. You have to introduce the proper
protection in the caller side.
thanks,
Takashi
> ---
> src/pcm/pcm_direct.c | 5 +++--
> 1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/src/pcm/pcm_direct.c b/src/pcm/pcm_direct.c
> index c3925cc20fd3..643498375b34 100644
> --- a/src/pcm/pcm_direct.c
> +++ b/src/pcm/pcm_direct.c
> @@ -96,11 +96,12 @@ int snd_pcm_direct_shm_create_or_connect(snd_pcm_direct_t *dmix)
> retryget:
> dmix->shmid = shmget(dmix->ipc_key, sizeof(snd_pcm_direct_share_t),
> dmix->ipc_perm);
> - if (dmix->shmid < 0) {
> - if (errno == ENOENT)
> + if (dmix->shmid < 0 && errno == ENOENT) {
> if ((dmix->shmid = shmget(dmix->ipc_key, sizeof(snd_pcm_direct_share_t),
> IPC_CREAT | IPC_EXCL | dmix->ipc_perm)) != -1)
> first_instance = 1;
> + else if (errno == EEXIST)
> + goto retryget;
> }
> err = -errno;
> if (dmix->shmid < 0) {
> --
> 2.9.2
>
_______________________________________________
Alsa-devel mailing list
Alsa-devel@xxxxxxxxxxxxxxxx
http://mailman.alsa-project.org/mailman/listinfo/alsa-devel
