| Message ID | BLU436-SMTP231971C20166F7E91EA3C9AD2B40@phx.gbl (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
Hi Takashi Iwai: Is this patch OK? I have automatically tested 422 times after this fix, and 'unable to create IPC shm instance' doesn't happen, and so the multimedia application functions properly. I would be very happy if I could do a bit contribution to the open source world! :) On 03/10/2016 08:40 PM, IceBsi wrote: > From: Qing Cai <bsiice@msn.com> > > As stated in manpage SHMCTL(2), shm_nattch is "No. of current attaches" > (i.e., number of processes attached to the shared memeory). If an > application uses alsa-lib and invokes fork() from a thread of the > application, there may be the following execution sequence: > 1. execute the following statement: > pcm_direct.c:110: dmix->shmptr = shmat(dmix->shmid, 0, 0) > (shm_nattch becomes 1) > 2. invoke fork() in some thread. > (shm_nattch becomes 2) > 3. execute the following statement: > pcm_direct.c:122: if (buf.shm_nattch == 1) > 4. execute the following statement: > pcm_direct.c:131: if (dmix->shmptr->magic != SND_PCM_DIRECT_MAGIC) > (As stated in manpage SHMGET(2), "When a new shared memory segment > is created, its contents are initialized to zero values", so > dmix->shmptr->magic is 0) > 5. execute the following statements: > pcm_direct.c:132: snd_pcm_direct_shm_discard(dmix) > pcm_direct.c:133: return -EINVAL > The above execution sequence will cause the following error: > unable to create IPC shm instance > This error causes multimedia application has no sound. This error rarely > occurs, probability is about 1%. > > Signed-off-by: Qing Cai <bsiice@msn.com> > Signed-off-by: Qing Cai <caiqing@neusoft.com> > > diff --git a/src/pcm/pcm_direct.c b/src/pcm/pcm_direct.c > index fd3877c..14de734 100644 > --- a/src/pcm/pcm_direct.c > +++ b/src/pcm/pcm_direct.c > @@ -91,13 +91,19 @@ int snd_pcm_direct_semaphore_create_or_connect(snd_pcm_direct_t *dmix) > int snd_pcm_direct_shm_create_or_connect(snd_pcm_direct_t *dmix) > { > struct shmid_ds buf; > - int tmpid, err; > + int tmpid, err, first_instance = 0; > > retryget: > dmix->shmid = shmget(dmix->ipc_key, sizeof(snd_pcm_direct_share_t), > - IPC_CREAT | dmix->ipc_perm); > + dmix->ipc_perm); > + if (dmix->shmid < 0) { > + if (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; > + } > err = -errno; > - if (dmix->shmid < 0){ > + if (dmix->shmid < 0) { > if (errno == EINVAL) > if ((tmpid = shmget(dmix->ipc_key, 0, dmix->ipc_perm)) != -1) > if (!shmctl(tmpid, IPC_STAT, &buf)) > @@ -119,7 +125,7 @@ retryget: > snd_pcm_direct_shm_discard(dmix); > return err; > } > - if (buf.shm_nattch == 1) { /* we're the first user, clear the segment */ > + if (first_instance) { /* we're the first user, clear the segment */ > memset(dmix->shmptr, 0, sizeof(snd_pcm_direct_share_t)); > if (dmix->ipc_gid >= 0) { > buf.shm_perm.gid = dmix->ipc_gid; >
On Thu, 10 Mar 2016 13:50:24 +0100, bsiice wrote: > > Hi Takashi Iwai: > > Is this patch OK? > > I have automatically tested 422 times after this fix, and > 'unable to create IPC shm instance' doesn't happen, and so the multimedia > application functions properly. The patch looks good, and working as far as I've tested, so merged to git tree now. I added a few more changelog texts to explain what exactly this patch does. > I would be very happy if I could do a bit contribution to the open source > world! :) Glad to have a really nice improvement, too. Thanks! Takashi > > > On 03/10/2016 08:40 PM, IceBsi wrote: > > From: Qing Cai <bsiice@msn.com> > > > > As stated in manpage SHMCTL(2), shm_nattch is "No. of current attaches" > > (i.e., number of processes attached to the shared memeory). If an > > application uses alsa-lib and invokes fork() from a thread of the > > application, there may be the following execution sequence: > > 1. execute the following statement: > > pcm_direct.c:110: dmix->shmptr = shmat(dmix->shmid, 0, 0) > > (shm_nattch becomes 1) > > 2. invoke fork() in some thread. > > (shm_nattch becomes 2) > > 3. execute the following statement: > > pcm_direct.c:122: if (buf.shm_nattch == 1) > > 4. execute the following statement: > > pcm_direct.c:131: if (dmix->shmptr->magic != SND_PCM_DIRECT_MAGIC) > > (As stated in manpage SHMGET(2), "When a new shared memory segment > > is created, its contents are initialized to zero values", so > > dmix->shmptr->magic is 0) > > 5. execute the following statements: > > pcm_direct.c:132: snd_pcm_direct_shm_discard(dmix) > > pcm_direct.c:133: return -EINVAL > > The above execution sequence will cause the following error: > > unable to create IPC shm instance > > This error causes multimedia application has no sound. This error rarely > > occurs, probability is about 1%. > > > > Signed-off-by: Qing Cai <bsiice@msn.com> > > Signed-off-by: Qing Cai <caiqing@neusoft.com> > > > > diff --git a/src/pcm/pcm_direct.c b/src/pcm/pcm_direct.c > > index fd3877c..14de734 100644 > > --- a/src/pcm/pcm_direct.c > > +++ b/src/pcm/pcm_direct.c > > @@ -91,13 +91,19 @@ int snd_pcm_direct_semaphore_create_or_connect(snd_pcm_direct_t *dmix) > > int snd_pcm_direct_shm_create_or_connect(snd_pcm_direct_t *dmix) > > { > > struct shmid_ds buf; > > - int tmpid, err; > > + int tmpid, err, first_instance = 0; > > > > retryget: > > dmix->shmid = shmget(dmix->ipc_key, sizeof(snd_pcm_direct_share_t), > > - IPC_CREAT | dmix->ipc_perm); > > + dmix->ipc_perm); > > + if (dmix->shmid < 0) { > > + if (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; > > + } > > err = -errno; > > - if (dmix->shmid < 0){ > > + if (dmix->shmid < 0) { > > if (errno == EINVAL) > > if ((tmpid = shmget(dmix->ipc_key, 0, dmix->ipc_perm)) != -1) > > if (!shmctl(tmpid, IPC_STAT, &buf)) > > @@ -119,7 +125,7 @@ retryget: > > snd_pcm_direct_shm_discard(dmix); > > return err; > > } > > - if (buf.shm_nattch == 1) { /* we're the first user, clear the segment */ > > + if (first_instance) { /* we're the first user, clear the segment */ > > memset(dmix->shmptr, 0, sizeof(snd_pcm_direct_share_t)); > > if (dmix->ipc_gid >= 0) { > > buf.shm_perm.gid = dmix->ipc_gid; > > >
On 03/10/2016 10:43 PM, Takashi Iwai wrote: > On Thu, 10 Mar 2016 13:50:24 +0100, > bsiice wrote: >> >> Hi Takashi Iwai: >> >> Is this patch OK? >> >> I have automatically tested 422 times after this fix, and >> 'unable to create IPC shm instance' doesn't happen, and so the multimedia >> application functions properly. > > The patch looks good, and working as far as I've tested, so merged to > git tree now. I added a few more changelog texts to explain what > exactly this patch does. Thanks a million for the changelog texts! Very glad and exciting with my patch is adopted! thanks, Qing Cai
diff --git a/src/pcm/pcm_direct.c b/src/pcm/pcm_direct.c index fd3877c..14de734 100644 --- a/src/pcm/pcm_direct.c +++ b/src/pcm/pcm_direct.c @@ -91,13 +91,19 @@ int snd_pcm_direct_semaphore_create_or_connect(snd_pcm_direct_t *dmix) int snd_pcm_direct_shm_create_or_connect(snd_pcm_direct_t *dmix) { struct shmid_ds buf; - int tmpid, err; + int tmpid, err, first_instance = 0; retryget: dmix->shmid = shmget(dmix->ipc_key, sizeof(snd_pcm_direct_share_t), - IPC_CREAT | dmix->ipc_perm); + dmix->ipc_perm); + if (dmix->shmid < 0) { + if (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; + } err = -errno; - if (dmix->shmid < 0){ + if (dmix->shmid < 0) { if (errno == EINVAL) if ((tmpid = shmget(dmix->ipc_key, 0, dmix->ipc_perm)) != -1) if (!shmctl(tmpid, IPC_STAT, &buf)) @@ -119,7 +125,7 @@ retryget: snd_pcm_direct_shm_discard(dmix); return err; } - if (buf.shm_nattch == 1) { /* we're the first user, clear the segment */ + if (first_instance) { /* we're the first user, clear the segment */ memset(dmix->shmptr, 0, sizeof(snd_pcm_direct_share_t)); if (dmix->ipc_gid >= 0) { buf.shm_perm.gid = dmix->ipc_gid;