[PATCH 0/3] ALSA: a few more USB-audio fixes
Hi,
here is a small patch set for USB-audio. The goal of this patch set is to cover a small race window at the endpoint state transition, and the preparation for the upcoming patch set for PCM sync_stop fixes.
Takashi
===
Takashi Iwai (3): ALSA: usb-audio: Handle invalid running state at releasing EP ALSA: usb-audio: More strict state change in EP ALSA: usb-audio: Don't avoid stopping the stream at disconnection
sound/usb/card.h | 2 +- sound/usb/endpoint.c | 85 +++++++++++++++++++++++++------------------- sound/usb/pcm.c | 5 +-- 3 files changed, 51 insertions(+), 41 deletions(-)
When we stop an endpoint in release_urbs(), it ignores the inconsistent endpoint state and tries to release the resources. This shouldn't happen in theory, but it's still safer to abort the release and let the caller proper error handling.
Also, stop_and_unlink_urbs() called from release_urbs() does two step works, and it's more straightforward to split this to two functions again, so that the call from the PCM trigger won't take the path with sleeping.
This patch modifies the EP management code to adapt two points above.
Fixes: d0f09d1e4a88 ("ALSA: usb-audio: Refactoring endpoint URB deactivation") Cc: stable@vger.kernel.org Signed-off-by: Takashi Iwai tiwai@suse.de --- sound/usb/endpoint.c | 40 +++++++++++++++++++++------------------- 1 file changed, 21 insertions(+), 19 deletions(-)
diff --git a/sound/usb/endpoint.c b/sound/usb/endpoint.c index 4d1c678a0d80..e102c024c21f 100644 --- a/sound/usb/endpoint.c +++ b/sound/usb/endpoint.c @@ -868,24 +868,22 @@ void snd_usb_endpoint_sync_pending_stop(struct snd_usb_endpoint *ep) }
/* - * Stop and unlink active urbs. + * Stop active urbs * - * This function checks and clears EP_FLAG_RUNNING state. - * When @wait_sync is set, it waits until all pending URBs are killed. + * This function moves the EP to STOPPING state if it's being RUNNING. */ -static int stop_and_unlink_urbs(struct snd_usb_endpoint *ep, bool force, - bool wait_sync) +static int stop_urbs(struct snd_usb_endpoint *ep, bool force) { unsigned int i;
if (!force && atomic_read(&ep->chip->shutdown)) /* to be sure... */ return -EBADFD;
- if (atomic_read(&ep->running)) + if (!force && atomic_read(&ep->running)) return -EBUSY;
if (!test_and_clear_bit(EP_FLAG_RUNNING, &ep->flags)) - goto out; + return 0;
set_bit(EP_FLAG_STOPPING, &ep->flags); INIT_LIST_HEAD(&ep->ready_playback_urbs); @@ -901,24 +899,25 @@ static int stop_and_unlink_urbs(struct snd_usb_endpoint *ep, bool force, } }
- out: - if (wait_sync) - return wait_clear_urbs(ep); return 0; }
/* * release an endpoint's urbs */ -static void release_urbs(struct snd_usb_endpoint *ep, int force) +static int release_urbs(struct snd_usb_endpoint *ep, bool force) { - int i; + int i, err;
/* route incoming urbs to nirvana */ snd_usb_endpoint_set_callback(ep, NULL, NULL, NULL);
- /* stop urbs */ - stop_and_unlink_urbs(ep, force, true); + /* stop and unlink urbs */ + err = stop_urbs(ep, force); + if (err) + return err; + + wait_clear_urbs(ep);
for (i = 0; i < ep->nurbs; i++) release_urb_ctx(&ep->urb[i]); @@ -928,6 +927,7 @@ static void release_urbs(struct snd_usb_endpoint *ep, int force)
ep->syncbuf = NULL; ep->nurbs = 0; + return 0; }
/* @@ -1118,7 +1118,7 @@ static int data_ep_set_params(struct snd_usb_endpoint *ep) return 0;
out_of_memory: - release_urbs(ep, 0); + release_urbs(ep, false); return -ENOMEM; }
@@ -1162,7 +1162,7 @@ static int sync_ep_set_params(struct snd_usb_endpoint *ep) return 0;
out_of_memory: - release_urbs(ep, 0); + release_urbs(ep, false); return -ENOMEM; }
@@ -1180,7 +1180,9 @@ static int snd_usb_endpoint_set_params(struct snd_usb_audio *chip, int err;
/* release old buffers, if any */ - release_urbs(ep, 0); + err = release_urbs(ep, false); + if (err < 0) + return err;
ep->datainterval = fmt->datainterval; ep->maxpacksize = fmt->maxpacksize; @@ -1433,7 +1435,7 @@ void snd_usb_endpoint_stop(struct snd_usb_endpoint *ep) WRITE_ONCE(ep->sync_source->sync_sink, NULL);
if (!atomic_dec_return(&ep->running)) - stop_and_unlink_urbs(ep, false, false); + stop_urbs(ep, false); }
/** @@ -1446,7 +1448,7 @@ void snd_usb_endpoint_stop(struct snd_usb_endpoint *ep) */ void snd_usb_endpoint_release(struct snd_usb_endpoint *ep) { - release_urbs(ep, 1); + release_urbs(ep, true); }
/**
The endpoint management has bit flags to indicate the current state, and we're dealing two things: the running bit and the stopping bit. There is a thin window in transition from the running to the stopping in stop_urbs(), and as long as the bit flags are used, it's difficult to plug.
This patch modifies the state management code to use the atomic int and follow the explicit three states, STOPPED, RUNNING and STOPPING. The state change is done via atomic_cmpxhg() for avoiding possible races, and check the state change more strictly. The unexpected state change is now handled as an error.
Fixes: d0f09d1e4a88 ("ALSA: usb-audio: Refactoring endpoint URB deactivation") Cc: stable@vger.kernel.org Signed-off-by: Takashi Iwai tiwai@suse.de --- sound/usb/card.h | 2 +- sound/usb/endpoint.c | 42 ++++++++++++++++++++++++++++-------------- 2 files changed, 29 insertions(+), 15 deletions(-)
diff --git a/sound/usb/card.h b/sound/usb/card.h index 37091b117614..a741e7da83a2 100644 --- a/sound/usb/card.h +++ b/sound/usb/card.h @@ -71,7 +71,7 @@ struct snd_usb_endpoint { unsigned char altsetting; /* corresponding alternate setting */ unsigned char ep_idx; /* endpoint array index */
- unsigned long flags; /* running bit flags */ + atomic_t state; /* running state */
void (*prepare_data_urb) (struct snd_usb_substream *subs, struct urb *urb); diff --git a/sound/usb/endpoint.c b/sound/usb/endpoint.c index e102c024c21f..4390075b2c6f 100644 --- a/sound/usb/endpoint.c +++ b/sound/usb/endpoint.c @@ -21,8 +21,11 @@ #include "clock.h" #include "quirks.h"
-#define EP_FLAG_RUNNING 1 -#define EP_FLAG_STOPPING 2 +enum { + EP_STATE_STOPPED, + EP_STATE_RUNNING, + EP_STATE_STOPPING, +};
/* interface refcounting */ struct snd_usb_iface_ref { @@ -115,6 +118,16 @@ static const char *usb_error_string(int err) } }
+static inline bool ep_state_running(struct snd_usb_endpoint *ep) +{ + return atomic_read(&ep->state) == EP_STATE_RUNNING; +} + +static inline bool ep_state_update(struct snd_usb_endpoint *ep, int old, int new) +{ + return atomic_cmpxchg(&ep->state, old, new) == old; +} + /** * snd_usb_endpoint_implicit_feedback_sink: Report endpoint usage type * @@ -393,7 +406,7 @@ next_packet_fifo_dequeue(struct snd_usb_endpoint *ep) */ static void queue_pending_output_urbs(struct snd_usb_endpoint *ep) { - while (test_bit(EP_FLAG_RUNNING, &ep->flags)) { + while (ep_state_running(ep)) {
unsigned long flags; struct snd_usb_packet_info *packet; @@ -454,13 +467,13 @@ static void snd_complete_urb(struct urb *urb) if (unlikely(atomic_read(&ep->chip->shutdown))) goto exit_clear;
- if (unlikely(!test_bit(EP_FLAG_RUNNING, &ep->flags))) + if (unlikely(!ep_state_running(ep))) goto exit_clear;
if (usb_pipeout(ep->pipe)) { retire_outbound_urb(ep, ctx); /* can be stopped during retire callback */ - if (unlikely(!test_bit(EP_FLAG_RUNNING, &ep->flags))) + if (unlikely(!ep_state_running(ep))) goto exit_clear;
if (snd_usb_endpoint_implicit_feedback_sink(ep)) { @@ -474,12 +487,12 @@ static void snd_complete_urb(struct urb *urb)
prepare_outbound_urb(ep, ctx); /* can be stopped during prepare callback */ - if (unlikely(!test_bit(EP_FLAG_RUNNING, &ep->flags))) + if (unlikely(!ep_state_running(ep))) goto exit_clear; } else { retire_inbound_urb(ep, ctx); /* can be stopped during retire callback */ - if (unlikely(!test_bit(EP_FLAG_RUNNING, &ep->flags))) + if (unlikely(!ep_state_running(ep))) goto exit_clear;
prepare_inbound_urb(ep, ctx); @@ -835,7 +848,7 @@ static int wait_clear_urbs(struct snd_usb_endpoint *ep) unsigned long end_time = jiffies + msecs_to_jiffies(1000); int alive;
- if (!test_bit(EP_FLAG_STOPPING, &ep->flags)) + if (atomic_read(&ep->state) != EP_STATE_STOPPING) return 0;
do { @@ -850,10 +863,11 @@ static int wait_clear_urbs(struct snd_usb_endpoint *ep) usb_audio_err(ep->chip, "timeout: still %d active urbs on EP #%x\n", alive, ep->ep_num); - clear_bit(EP_FLAG_STOPPING, &ep->flags);
- ep->sync_sink = NULL; - snd_usb_endpoint_set_callback(ep, NULL, NULL, NULL); + if (ep_state_update(ep, EP_STATE_STOPPING, EP_STATE_STOPPED)) { + ep->sync_sink = NULL; + snd_usb_endpoint_set_callback(ep, NULL, NULL, NULL); + }
return 0; } @@ -882,10 +896,9 @@ static int stop_urbs(struct snd_usb_endpoint *ep, bool force) if (!force && atomic_read(&ep->running)) return -EBUSY;
- if (!test_and_clear_bit(EP_FLAG_RUNNING, &ep->flags)) + if (!ep_state_update(ep, EP_STATE_RUNNING, EP_STATE_STOPPING)) return 0;
- set_bit(EP_FLAG_STOPPING, &ep->flags); INIT_LIST_HEAD(&ep->ready_playback_urbs); ep->next_packet_head = 0; ep->next_packet_queued = 0; @@ -1362,7 +1375,8 @@ int snd_usb_endpoint_start(struct snd_usb_endpoint *ep) * from that context. */
- set_bit(EP_FLAG_RUNNING, &ep->flags); + if (!ep_state_update(ep, EP_STATE_STOPPED, EP_STATE_RUNNING)) + goto __error;
if (snd_usb_endpoint_implicit_feedback_sink(ep)) { for (i = 0; i < ep->nurbs; i++) {
In the later patch, we're going to issue the PCM sync_stop calls at disconnection. But currently the USB-audio driver can't handle it because it has a check of shutdown flag for stopping the URBs. This is basically superfluous (the stopping URBs are safe at disconnection state), so let's drop the check.
Fixes: dc5eafe7787c ("ALSA: usb-audio: Support PCM sync_stop") Cc: stable@vger.kernel.org Signed-off-by: Takashi Iwai tiwai@suse.de --- sound/usb/endpoint.c | 3 --- sound/usb/pcm.c | 5 +---- 2 files changed, 1 insertion(+), 7 deletions(-)
diff --git a/sound/usb/endpoint.c b/sound/usb/endpoint.c index 4390075b2c6f..102d53515a76 100644 --- a/sound/usb/endpoint.c +++ b/sound/usb/endpoint.c @@ -890,9 +890,6 @@ static int stop_urbs(struct snd_usb_endpoint *ep, bool force) { unsigned int i;
- if (!force && atomic_read(&ep->chip->shutdown)) /* to be sure... */ - return -EBADFD; - if (!force && atomic_read(&ep->running)) return -EBUSY;
diff --git a/sound/usb/pcm.c b/sound/usb/pcm.c index dcadf8f164b2..bf5a0f3c1fad 100644 --- a/sound/usb/pcm.c +++ b/sound/usb/pcm.c @@ -270,10 +270,7 @@ static int snd_usb_pcm_sync_stop(struct snd_pcm_substream *substream) { struct snd_usb_substream *subs = substream->runtime->private_data;
- if (!snd_usb_lock_shutdown(subs->stream->chip)) { - sync_pending_stops(subs); - snd_usb_unlock_shutdown(subs->stream->chip); - } + sync_pending_stops(subs); return 0; }
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Takashi Iwai