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authorIoan-Adrian Ratiu <adi@adirat.com>2017-01-04 23:37:46 +0100
committerTakashi Iwai <tiwai@suse.de>2017-01-05 07:35:00 +0100
commit1d0f953086f090a022f2c0e1448300c15372db46 (patch)
tree96e89154873d3b08b73e18d717e33631cb050f67 /sound/usb/pcm.c
parentALSA: hda - Apply asus-mode8 fixup to ASUS X71SL (diff)
downloadlinux-1d0f953086f090a022f2c0e1448300c15372db46.tar.xz
linux-1d0f953086f090a022f2c0e1448300c15372db46.zip
ALSA: usb-audio: Fix irq/process data synchronization
Commit 16200948d83 ("ALSA: usb-audio: Fix race at stopping the stream") was incomplete causing another more severe kernel panic, so it got reverted. This fixes both the original problem and its fallout kernel race/crash. The original fix is to move the endpoint member NULL clearing logic inside wait_clear_urbs() so the irq triggering the urb completion doesn't call retire_capture/playback_urb() after the NULL clearing and generate a panic. However this creates a new race between snd_usb_endpoint_start()'s call to wait_clear_urbs() and the irq urb completion handler which again calls retire_capture/playback_urb() leading to a new NULL dereference. We keep the EP deactivation code in snd_usb_endpoint_start() because removing it will break the EP reference counting (see [1] [2] for info), however we don't need the "can_sleep" mechanism anymore because a new function was introduced (snd_usb_endpoint_sync_pending_stop()) which synchronizes pending stops and gets called inside the pcm prepare callback. It also makes sense to remove can_sleep because it was also removed from deactivate_urbs() signature in [3] so we benefit from more simplification. [1] commit 015618b90 ("ALSA: snd-usb: Fix URB cancellation at stream start") [2] commit e9ba389c5 ("ALSA: usb-audio: Fix scheduling-while-atomic bug in PCM capture stream") [3] commit ccc1696d5 ("ALSA: usb-audio: simplify endpoint deactivation code") Fixes: f8114f8583bb ("Revert "ALSA: usb-audio: Fix race at stopping the stream"") Signed-off-by: Ioan-Adrian Ratiu <adi@adirat.com> Signed-off-by: Takashi Iwai <tiwai@suse.de>
Diffstat (limited to '')
-rw-r--r--sound/usb/pcm.c10
1 files changed, 5 insertions, 5 deletions
diff --git a/sound/usb/pcm.c b/sound/usb/pcm.c
index 34c6d4f2c0b6..9aa5b1855481 100644
--- a/sound/usb/pcm.c
+++ b/sound/usb/pcm.c
@@ -218,7 +218,7 @@ int snd_usb_init_pitch(struct snd_usb_audio *chip, int iface,
}
}
-static int start_endpoints(struct snd_usb_substream *subs, bool can_sleep)
+static int start_endpoints(struct snd_usb_substream *subs)
{
int err;
@@ -231,7 +231,7 @@ static int start_endpoints(struct snd_usb_substream *subs, bool can_sleep)
dev_dbg(&subs->dev->dev, "Starting data EP @%p\n", ep);
ep->data_subs = subs;
- err = snd_usb_endpoint_start(ep, can_sleep);
+ err = snd_usb_endpoint_start(ep);
if (err < 0) {
clear_bit(SUBSTREAM_FLAG_DATA_EP_STARTED, &subs->flags);
return err;
@@ -260,7 +260,7 @@ static int start_endpoints(struct snd_usb_substream *subs, bool can_sleep)
dev_dbg(&subs->dev->dev, "Starting sync EP @%p\n", ep);
ep->sync_slave = subs->data_endpoint;
- err = snd_usb_endpoint_start(ep, can_sleep);
+ err = snd_usb_endpoint_start(ep);
if (err < 0) {
clear_bit(SUBSTREAM_FLAG_SYNC_EP_STARTED, &subs->flags);
return err;
@@ -850,7 +850,7 @@ static int snd_usb_pcm_prepare(struct snd_pcm_substream *substream)
/* for playback, submit the URBs now; otherwise, the first hwptr_done
* updates for all URBs would happen at the same time when starting */
if (subs->direction == SNDRV_PCM_STREAM_PLAYBACK)
- ret = start_endpoints(subs, true);
+ ret = start_endpoints(subs);
unlock:
snd_usb_unlock_shutdown(subs->stream->chip);
@@ -1666,7 +1666,7 @@ static int snd_usb_substream_capture_trigger(struct snd_pcm_substream *substream
switch (cmd) {
case SNDRV_PCM_TRIGGER_START:
- err = start_endpoints(subs, false);
+ err = start_endpoints(subs);
if (err < 0)
return err;