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authorTakashi Iwai <tiwai@suse.de>2019-02-06 07:30:44 +0100
committerTakashi Iwai <tiwai@suse.de>2019-02-08 16:54:31 +0100
commit00a399cad1a063e7665f06b6497a807db20441fd (patch)
tree8f2a341d6882481c2cccc2523912e06f7cba65ec /sound
parent0a5cf9e88b5178d15f00f3cf35081841d80403cd (diff)
ALSA: pcm: Revert capture stream behavior change in blocking mode
In the commit 62ba568f7aef ("ALSA: pcm: Return 0 when size < start_threshold in capture"), we changed the behavior of __snd_pcm_lib_xfer() to return immediately with 0 when a capture stream has a high start_threshold. This was intended to be a correction of the behavior consistency and looked harmless, but this was the culprit of the recent breakage reported by syzkaller, which was fixed by the commit e190161f96b8 ("ALSA: pcm: Fix tight loop of OSS capture stream"). At the time for the OSS fix, I didn't touch the behavior for ALSA native API, as assuming that this behavior actually is good. But this turned out to be also broken actually for a similar deployment, e.g. one thread goes to a write loop in blocking mode while another thread controls the start/stop of the stream manually. Overall, the original commit is harmful, and it brings less merit to keep that behavior. Let's revert it. Fixes: 62ba568f7aef ("ALSA: pcm: Return 0 when size < start_threshold in capture") Fixes: e190161f96b8 ("ALSA: pcm: Fix tight loop of OSS capture stream") Cc: <stable@vger.kernel.org> Signed-off-by: Takashi Iwai <tiwai@suse.de>
Diffstat (limited to 'sound')
-rw-r--r--sound/core/pcm_lib.c20
1 files changed, 4 insertions, 16 deletions
diff --git a/sound/core/pcm_lib.c b/sound/core/pcm_lib.c
index 6c99fa8ac5fa..6c0b30391ba9 100644
--- a/sound/core/pcm_lib.c
+++ b/sound/core/pcm_lib.c
@@ -2112,13 +2112,6 @@ int pcm_lib_apply_appl_ptr(struct snd_pcm_substream *substream,
return 0;
}
-/* allow waiting for a capture stream that hasn't been started */
-#if IS_ENABLED(CONFIG_SND_PCM_OSS)
-#define wait_capture_start(substream) ((substream)->oss.oss)
-#else
-#define wait_capture_start(substream) false
-#endif
-
/* the common loop for read/write data */
snd_pcm_sframes_t __snd_pcm_lib_xfer(struct snd_pcm_substream *substream,
void *data, bool interleaved,
@@ -2184,16 +2177,11 @@ snd_pcm_sframes_t __snd_pcm_lib_xfer(struct snd_pcm_substream *substream,
snd_pcm_update_hw_ptr(substream);
if (!is_playback &&
- runtime->status->state == SNDRV_PCM_STATE_PREPARED) {
- if (size >= runtime->start_threshold) {
- err = snd_pcm_start(substream);
- if (err < 0)
- goto _end_unlock;
- } else if (!wait_capture_start(substream)) {
- /* nothing to do */
- err = 0;
+ runtime->status->state == SNDRV_PCM_STATE_PREPARED &&
+ size >= runtime->start_threshold) {
+ err = snd_pcm_start(substream);
+ if (err < 0)
goto _end_unlock;
- }
}
avail = snd_pcm_avail(substream);