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At Thu, 08 Nov 2012 08:31:35 +0100,
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Daniel Mack wrote:
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(snip)
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> >> We can't simply stop both endpoints in the prepare callback.
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> >
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> > The new function doesn't stop the stream by itself but it just syncs
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> > if the stream is being stopped beforehand. So, it's safe to call it
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> > there.
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> >
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> > Maybe the name was confusing. It should have been like
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> > snd_usb_endpoint_sync_pending_stop() or such.
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>
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> Ah, right. I was errornously looking closer to Alan's patch but then
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> replied to yours. Alright then - thanks for explaining :)
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OK, thanks for checking.
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FWIW, below is the patch I applied now to for-linus branch.
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Renamed the function, added the comment and put NULL check to the
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function to simplify.
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Takashi
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---
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From: Takashi Iwai <tiwai@suse.de>
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Subject: [PATCH] ALSA: usb-audio: Fix crash at re-preparing the PCM stream
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There are bug reports of a crash with USB-audio devices when PCM
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prepare is performed immediately after the stream is stopped via
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trigger callback. It turned out that the problem is that we don't
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wait until all URBs are killed.
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This patch adds a new function to synchronize the pending stop
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operation on an endpoint, and calls in the prepare callback for
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avoiding the crash above.
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Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=49181
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Reported-and-tested-by: Artem S. Tashkinov <t.artem@lycos.com>
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Cc: <stable@vger.kernel.org> [v3.6]
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Signed-off-by: Takashi Iwai <tiwai@suse.de>
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---
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sound/usb/endpoint.c | 13 +++++++++++++
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sound/usb/endpoint.h | 1 +
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sound/usb/pcm.c | 3 +++
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3 files changed, 17 insertions(+)
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diff --git a/sound/usb/endpoint.c b/sound/usb/endpoint.c
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index 7f78c6d..34de6f2 100644
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--- a/sound/usb/endpoint.c
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+++ b/sound/usb/endpoint.c
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@@ -35,6 +35,7 @@
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#define EP_FLAG_ACTIVATED 0
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#define EP_FLAG_RUNNING 1
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+#define EP_FLAG_STOPPING 2
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/*
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* snd_usb_endpoint is a model that abstracts everything related to an
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@@ -502,10 +503,20 @@ static int wait_clear_urbs(struct snd_usb_endpoint *ep)
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if (alive)
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snd_printk(KERN_ERR "timeout: still %d active urbs on EP #%x\n",
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alive, ep->ep_num);
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+ clear_bit(EP_FLAG_STOPPING, &ep->flags);
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return 0;
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}
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+/* sync the pending stop operation;
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+ * this function itself doesn't trigger the stop operation
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+ */
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+void snd_usb_endpoint_sync_pending_stop(struct snd_usb_endpoint *ep)
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+{
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+ if (ep && test_bit(EP_FLAG_STOPPING, &ep->flags))
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+ wait_clear_urbs(ep);
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+}
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+
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/*
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* unlink active urbs.
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*/
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@@ -918,6 +929,8 @@ void snd_usb_endpoint_stop(struct snd_usb_endpoint *ep,
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if (wait)
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wait_clear_urbs(ep);
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+ else
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+ set_bit(EP_FLAG_STOPPING, &ep->flags);
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}
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}
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diff --git a/sound/usb/endpoint.h b/sound/usb/endpoint.h
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index 6376ccf..3d4c970 100644
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--- a/sound/usb/endpoint.h
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+++ b/sound/usb/endpoint.h
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@@ -19,6 +19,7 @@ int snd_usb_endpoint_set_params(struct snd_usb_endpoint *ep,
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int snd_usb_endpoint_start(struct snd_usb_endpoint *ep, int can_sleep);
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void snd_usb_endpoint_stop(struct snd_usb_endpoint *ep,
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int force, int can_sleep, int wait);
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+void snd_usb_endpoint_sync_pending_stop(struct snd_usb_endpoint *ep);
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int snd_usb_endpoint_activate(struct snd_usb_endpoint *ep);
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int snd_usb_endpoint_deactivate(struct snd_usb_endpoint *ep);
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void snd_usb_endpoint_free(struct list_head *head);
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diff --git a/sound/usb/pcm.c b/sound/usb/pcm.c
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index 37428f7..5c12a3f 100644
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--- a/sound/usb/pcm.c
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+++ b/sound/usb/pcm.c
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@@ -552,6 +552,9 @@ static int snd_usb_pcm_prepare(struct snd_pcm_substream *substream)
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if (snd_BUG_ON(!subs->data_endpoint))
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return -EIO;
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+ snd_usb_endpoint_sync_pending_stop(subs->sync_endpoint);
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+ snd_usb_endpoint_sync_pending_stop(subs->data_endpoint);
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+
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/* some unit conversions in runtime */
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subs->data_endpoint->maxframesize =
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bytes_to_frames(runtime, subs->data_endpoint->maxpacksize);
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--
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1.8.0
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--
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