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

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>

diff --git a/src/pcm/pcm_dmix.c b/src/pcm/pcm_dmix.c
index b26a5c790e7e1ffe778167e45c84f0af6eb8c62e..007d35664ce7635296b215e5fda038910aeae6dd 100644 (file)
--- a/src/pcm/pcm_dmix.c
+++ b/src/pcm/pcm_dmix.c
@@ -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;
                        }

diff --git a/src/pcm/pcm_dshare.c b/src/pcm/pcm_dshare.c
index 58e47bbeac677826acea97a29d1de89f0ee1f976..adb3587a2869143b985f2fff5e15f786ee52fde9 100644 (file)
--- a/src/pcm/pcm_dshare.c
+++ b/src/pcm/pcm_dshare.c
@@ -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;
                        }

diff --git a/src/pcm/pcm_dsnoop.c b/src/pcm/pcm_dsnoop.c
index 576c35b111cd473d7be8c585a5961f230b72cc20..8ff0ba57cb144b808f87223e9edcf7ca2164fdd1 100644 (file)
--- a/src/pcm/pcm_dsnoop.c
+++ b/src/pcm/pcm_dsnoop.c
@@ -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;
                        }