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pcm: Fix shm initialization race-condition

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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: dec428c352 ("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@iodev.co.uk>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
This commit is contained in:
Ismael Luceno 2016-08-22 13:04:33 -03:00 • committed by Takashi Iwai
parent e2cfe3c6c8
commit 7640856769
1 changed files with 3 additions and 2 deletions
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5
src/pcm/pcm_direct.c
View file

@ -96,11 +96,12 @@ int snd_pcm_direct_shm_create_or_connect(snd_pcm_direct_t *dmix)
retryget: retryget:
dmix->shmid = shmget(dmix->ipc_key, sizeof(snd_pcm_direct_share_t), dmix->shmid = shmget(dmix->ipc_key, sizeof(snd_pcm_direct_share_t),
dmix->ipc_perm); dmix->ipc_perm);
if (dmix->shmid < 0) { if (dmix->shmid < 0 && errno == ENOENT) {
if (errno == ENOENT)
if ((dmix->shmid = shmget(dmix->ipc_key, sizeof(snd_pcm_direct_share_t), if ((dmix->shmid = shmget(dmix->ipc_key, sizeof(snd_pcm_direct_share_t),
IPC_CREAT | IPC_EXCL | dmix->ipc_perm)) != -1) IPC_CREAT | IPC_EXCL | dmix->ipc_perm)) != -1)
first_instance = 1; first_instance = 1;
else if (errno == EEXIST)
goto retryget;
} }
err = -errno; err = -errno;
if (dmix->shmid < 0) { if (dmix->shmid < 0) {