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authorTakashi Iwai <tiwai@suse.de>2020-02-14 18:16:43 +0100
committerTakashi Iwai <tiwai@suse.de>2020-02-14 18:17:13 +0100
commit146f66975bafbcfab349901c9f9c9f521ac96cbb (patch)
tree0463626fdde9562d85dcabb03b85b8bfd929dce0
parente9a0ef0b5ddcbc0d56c65aefc0f18d16e6f71207 (diff)
downloadlinux-146f66975bafbcfab349901c9f9c9f521ac96cbb.tar.bz2
ALSA: pcm: oss: Unlock mutex temporarily for sleeping at read/write
ALSA PCM OSS layer calls the generic __snd_pcm_lib_xfer() helper for the actual transfer of the audio data. The xfer helper may sleep long for waiting for the enough space becoming empty for read/write, and it does unlock/relock for the substream lock. This works fine, so far, but a slight problem specific to OSS layer is that OSS layer wraps yet more mutex (runtime->oss.params_lock) over __snd_pcm_lib_xfer() call; so this mutex is still locked during a possible long sleep, and it prevents the whole ioctl and other actions applied to the given stream. This patch adds the temporarily unlock and relock of the mutex around __snd_pcm_lib_xfer() call in the OSS layer to be more friendly to the concurrent accesses. The long mutex protection itself shouldn't be a real issue for the normal systems, and its influence appears only on strange things like fuzzers. Link: https://lore.kernel.org/r/20200214171643.26212-1-tiwai@suse.de Signed-off-by: Takashi Iwai <tiwai@suse.de>
-rw-r--r--sound/core/oss/pcm_oss.c4
1 files changed, 4 insertions, 0 deletions
diff --git a/sound/core/oss/pcm_oss.c b/sound/core/oss/pcm_oss.c
index 707eb2a9d50c..930def8201f4 100644
--- a/sound/core/oss/pcm_oss.c
+++ b/sound/core/oss/pcm_oss.c
@@ -1217,8 +1217,10 @@ snd_pcm_sframes_t snd_pcm_oss_write3(struct snd_pcm_substream *substream, const
if (ret < 0)
break;
}
+ mutex_unlock(&runtime->oss.params_lock);
ret = __snd_pcm_lib_xfer(substream, (void *)ptr, true,
frames, in_kernel);
+ mutex_lock(&runtime->oss.params_lock);
if (ret != -EPIPE && ret != -ESTRPIPE)
break;
/* test, if we can't store new data, because the stream */
@@ -1254,8 +1256,10 @@ snd_pcm_sframes_t snd_pcm_oss_read3(struct snd_pcm_substream *substream, char *p
ret = snd_pcm_oss_capture_position_fixup(substream, &delay);
if (ret < 0)
break;
+ mutex_unlock(&runtime->oss.params_lock);
ret = __snd_pcm_lib_xfer(substream, (void *)ptr, true,
frames, in_kernel);
+ mutex_lock(&runtime->oss.params_lock);
if (ret == -EPIPE) {
if (runtime->status->state == SNDRV_PCM_STATE_DRAINING) {
ret = snd_pcm_kernel_ioctl(substream, SNDRV_PCM_IOCTL_DROP, NULL);