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From: Takashi Iwai <tiwai@suse.de>
To: alsa-devel@alsa-project.org
Cc: Matwey Kornilov <matwey.kornilov@gmail.com>,
	Dylan Robinson <dylan_robinson@motu.com>,
	Keith Milner <kamilner@superlative.org>
Subject: [PATCH 26/41] ALSA: usb-audio: Fix possible stall of implicit fb packet ring-buffer
Date: Mon, 23 Nov 2020 09:53:32 +0100	[thread overview]
Message-ID: <20201123085347.19667-27-tiwai@suse.de> (raw)
In-Reply-To: <20201123085347.19667-1-tiwai@suse.de>

The implicit feedback mode uses a ring buffer for storing the received
packet sizes from the feedback source, and the code has a slight flaw;
when a playback stream stalls by some reason and the URBs aren't
processed, the next_packet FIFO might become empty, but the driver
can't distinguish whether it's empty or full because it's managed with
read_poss and write_pos.

This patch addresses those by changing the next_packet array
management.  Instead of keeping read and write positions, now the head
position and the queued amount are kept.  It's easier to understand
about the emptiness.  Also, the URB active flag is now cleared before
calling queue_pending_output_urbs() for avoiding (theoretically)
possible inconsistency.

Tested-by: Keith Milner <kamilner@superlative.org>
Tested-by: Dylan Robinson <dylan_robinson@motu.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
---
 sound/usb/card.h     |  5 ++--
 sound/usb/endpoint.c | 83 +++++++++++++++++++++++++++++++++++++---------------
 2 files changed, 63 insertions(+), 25 deletions(-)

diff --git a/sound/usb/card.h b/sound/usb/card.h
index 66a249ae138f..cde492e9581a 100644
--- a/sound/usb/card.h
+++ b/sound/usb/card.h
@@ -80,8 +80,9 @@ struct snd_usb_endpoint {
 		uint32_t packet_size[MAX_PACKS_HS];
 		int packets;
 	} next_packet[MAX_URBS];
-	int next_packet_read_pos, next_packet_write_pos;
-	struct list_head ready_playback_urbs;
+	unsigned int next_packet_head;	/* ring buffer offset to read */
+	unsigned int next_packet_queued; /* queued items in the ring buffer */
+	struct list_head ready_playback_urbs; /* playback URB FIFO for implicit fb */
 
 	unsigned int nurbs;		/* # urbs */
 	unsigned long active_mask;	/* bitmask of active urbs */
diff --git a/sound/usb/endpoint.c b/sound/usb/endpoint.c
index eee74313603e..b8f06a75fc2a 100644
--- a/sound/usb/endpoint.c
+++ b/sound/usb/endpoint.c
@@ -328,6 +328,39 @@ static inline void prepare_inbound_urb(struct snd_usb_endpoint *ep,
 	}
 }
 
+/* notify an error as XRUN to the assigned PCM data substream */
+static void notify_xrun(struct snd_usb_endpoint *ep)
+{
+	struct snd_usb_substream *data_subs;
+
+	data_subs = READ_ONCE(ep->data_subs);
+	if (data_subs && data_subs->pcm_substream)
+		snd_pcm_stop_xrun(data_subs->pcm_substream);
+}
+
+static struct snd_usb_packet_info *
+next_packet_fifo_enqueue(struct snd_usb_endpoint *ep)
+{
+	struct snd_usb_packet_info *p;
+
+	p = ep->next_packet + (ep->next_packet_head + ep->next_packet_queued) %
+		ARRAY_SIZE(ep->next_packet);
+	ep->next_packet_queued++;
+	return p;
+}
+
+static struct snd_usb_packet_info *
+next_packet_fifo_dequeue(struct snd_usb_endpoint *ep)
+{
+	struct snd_usb_packet_info *p;
+
+	p = ep->next_packet + ep->next_packet_head;
+	ep->next_packet_head++;
+	ep->next_packet_head %= ARRAY_SIZE(ep->next_packet);
+	ep->next_packet_queued--;
+	return p;
+}
+
 /*
  * Send output urbs that have been prepared previously. URBs are dequeued
  * from ep->ready_playback_urbs and in case there aren't any available
@@ -352,17 +385,14 @@ static void queue_pending_output_urbs(struct snd_usb_endpoint *ep)
 		int err, i;
 
 		spin_lock_irqsave(&ep->lock, flags);
-		if (ep->next_packet_read_pos != ep->next_packet_write_pos) {
-			packet = ep->next_packet + ep->next_packet_read_pos;
-			ep->next_packet_read_pos++;
-			ep->next_packet_read_pos %= MAX_URBS;
-
+		if (ep->next_packet_queued > 0 &&
+		    !list_empty(&ep->ready_playback_urbs)) {
 			/* take URB out of FIFO */
-			if (!list_empty(&ep->ready_playback_urbs)) {
-				ctx = list_first_entry(&ep->ready_playback_urbs,
+			ctx = list_first_entry(&ep->ready_playback_urbs,
 					       struct snd_urb_ctx, ready_list);
-				list_del_init(&ctx->ready_list);
-			}
+			list_del_init(&ctx->ready_list);
+
+			packet = next_packet_fifo_dequeue(ep);
 		}
 		spin_unlock_irqrestore(&ep->lock, flags);
 
@@ -377,12 +407,15 @@ static void queue_pending_output_urbs(struct snd_usb_endpoint *ep)
 		prepare_outbound_urb(ep, ctx);
 
 		err = usb_submit_urb(ctx->urb, GFP_ATOMIC);
-		if (err < 0)
+		if (err < 0) {
 			usb_audio_err(ep->chip,
 				      "Unable to submit urb #%d: %d at %s\n",
 				      ctx->index, err, __func__);
-		else
-			set_bit(ctx->index, &ep->active_mask);
+			notify_xrun(ep);
+			return;
+		}
+
+		set_bit(ctx->index, &ep->active_mask);
 	}
 }
 
@@ -393,7 +426,6 @@ static void snd_complete_urb(struct urb *urb)
 {
 	struct snd_urb_ctx *ctx = urb->context;
 	struct snd_usb_endpoint *ep = ctx->ep;
-	struct snd_usb_substream *data_subs;
 	unsigned long flags;
 	int err;
 
@@ -418,10 +450,10 @@ static void snd_complete_urb(struct urb *urb)
 		if (snd_usb_endpoint_implicit_feedback_sink(ep)) {
 			spin_lock_irqsave(&ep->lock, flags);
 			list_add_tail(&ctx->ready_list, &ep->ready_playback_urbs);
+			clear_bit(ctx->index, &ep->active_mask);
 			spin_unlock_irqrestore(&ep->lock, flags);
 			queue_pending_output_urbs(ep);
-
-			goto exit_clear;
+			return;
 		}
 
 		prepare_outbound_urb(ep, ctx);
@@ -442,9 +474,7 @@ static void snd_complete_urb(struct urb *urb)
 		return;
 
 	usb_audio_err(ep->chip, "cannot submit urb (err = %d)\n", err);
-	data_subs = READ_ONCE(ep->data_subs);
-	if (data_subs && data_subs->pcm_substream)
-		snd_pcm_stop_xrun(data_subs->pcm_substream);
+	notify_xrun(ep);
 
 exit_clear:
 	clear_bit(ctx->index, &ep->active_mask);
@@ -789,8 +819,8 @@ static int deactivate_urbs(struct snd_usb_endpoint *ep, bool force)
 	clear_bit(EP_FLAG_RUNNING, &ep->flags);
 
 	INIT_LIST_HEAD(&ep->ready_playback_urbs);
-	ep->next_packet_read_pos = 0;
-	ep->next_packet_write_pos = 0;
+	ep->next_packet_head = 0;
+	ep->next_packet_queued = 0;
 
 	for (i = 0; i < ep->nurbs; i++) {
 		if (test_bit(i, &ep->active_mask)) {
@@ -1402,7 +1432,16 @@ static void snd_usb_handle_sync_urb(struct snd_usb_endpoint *ep,
 			return;
 
 		spin_lock_irqsave(&ep->lock, flags);
-		out_packet = ep->next_packet + ep->next_packet_write_pos;
+		if (ep->next_packet_queued >= ARRAY_SIZE(ep->next_packet)) {
+			spin_unlock_irqrestore(&ep->lock, flags);
+			usb_audio_err(ep->chip,
+				      "next package FIFO overflow EP 0x%x\n",
+				      ep->ep_num);
+			notify_xrun(ep);
+			return;
+		}
+
+		out_packet = next_packet_fifo_enqueue(ep);
 
 		/*
 		 * Iterate through the inbound packet and prepare the lengths
@@ -1423,8 +1462,6 @@ static void snd_usb_handle_sync_urb(struct snd_usb_endpoint *ep,
 				out_packet->packet_size[i] = 0;
 		}
 
-		ep->next_packet_write_pos++;
-		ep->next_packet_write_pos %= MAX_URBS;
 		spin_unlock_irqrestore(&ep->lock, flags);
 		queue_pending_output_urbs(ep);
 
-- 
2.16.4


  parent reply	other threads:[~2020-11-23  9:04 UTC|newest]

Thread overview: 52+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-11-23  8:53 [PATCH 00/41] USB audio refactoring for better implicit feedback support Takashi Iwai
2020-11-23  8:53 ` [PATCH 01/41] ALSA: usb-audio: Handle discrete rates properly in hw constraints Takashi Iwai
2020-11-23  8:53 ` [PATCH 02/41] ALSA: usb-audio: Don't call usb_set_interface() at trigger callback Takashi Iwai
2020-11-23  8:53 ` [PATCH 03/41] ALSA: usb-audio: Check valid altsetting at parsing rates for UAC2/3 Takashi Iwai
2020-11-23  8:53 ` [PATCH 04/41] ALSA: usb-audio: Check implicit feedback EP generically for UAC2 Takashi Iwai
2020-11-23  8:53 ` [PATCH 05/41] ALSA: usb-audio: Add snd_usb_get_endpoint() helper Takashi Iwai
2020-11-23  8:53 ` [PATCH 06/41] ALSA: usb-audio: Set and clear sync EP link properly Takashi Iwai
2020-11-23  8:53 ` [PATCH 07/41] ALSA: usb-audio: Improve some debug prints Takashi Iwai
2020-11-23  8:53 ` [PATCH 08/41] ALSA: usb-audio: Track implicit fb sync endpoint in audioformat list Takashi Iwai
2020-11-23  8:53 ` [PATCH 09/41] ALSA: usb-audio: Move snd_usb_autoresume() call out of setup_hw_info() Takashi Iwai
2020-11-23  8:53 ` [PATCH 10/41] ALSA: usb-audio: Add hw constraint for implicit fb sync Takashi Iwai
2020-11-23  8:53 ` [PATCH 11/41] ALSA: usb-audio: Simplify hw_params rules Takashi Iwai
2020-11-23  8:53 ` [PATCH 12/41] ALSA: usb-audio: Drop debug.h Takashi Iwai
2020-11-23  8:53 ` [PATCH 13/41] ALSA: usb-audio: Avoid doubly initialization for implicit fb Takashi Iwai
2020-11-23  8:53 ` [PATCH 14/41] ALSA: usb-audio: Create endpoint objects at parsing phase Takashi Iwai
2021-01-03 17:09   ` [PATCH 14/41] ALSA: usb-audio: Create endpoint objects at parsing phase - Pioneer DJ DJM-250MK2 stopped working František Kučera
2021-01-03 17:19     ` Takashi Iwai
2021-01-03 18:15       ` František Kučera
2021-01-05  9:29         ` Takashi Iwai
2021-01-05 13:20           ` Takashi Iwai
2021-01-05 22:27             ` František Kučera
2021-01-06  9:03               ` Takashi Iwai
2021-01-06 19:01                 ` František Kučera
2021-01-07 13:30                   ` Takashi Iwai
2020-11-23  8:53 ` [PATCH 15/41] ALSA: usb-audio: Drop keep_interface flag again Takashi Iwai
2020-11-23  8:53 ` [PATCH 16/41] ALSA: usb-audio: Add snd_usb_get_host_interface() helper Takashi Iwai
2020-11-23  8:53 ` [PATCH 17/41] ALSA: usb-audio: Don't set altsetting before initializing sample rate Takashi Iwai
2020-11-23  8:53 ` [PATCH 18/41] ALSA: usb-audio: Pass snd_usb_audio object to quirk functions Takashi Iwai
2020-11-23  8:53 ` [PATCH 19/41] ALSA: usb-audio: Simplify snd_usb_init_sample_rate() arguments Takashi Iwai
2020-11-23  8:53 ` [PATCH 20/41] ALSA: usb-audio: Simplify snd_usb_init_pitch() arguments Takashi Iwai
2020-11-23  8:53 ` [PATCH 21/41] ALSA: usb-audio: Stop both endpoints properly at error Takashi Iwai
2020-11-23  8:53 ` [PATCH 22/41] ALSA: usb-audio: Set callbacks via snd_usb_endpoint_set_callback() Takashi Iwai
2020-11-23  8:53 ` [PATCH 23/41] ALSA: usb-audio: Always set up the parameters after resume Takashi Iwai
2020-11-23  8:53 ` [PATCH 24/41] ALSA: usb-audio: Fix EP matching for continuous rates Takashi Iwai
2020-11-23  8:53 ` [PATCH 25/41] ALSA: usb-audio: Refactor endpoint management Takashi Iwai
2020-11-23  8:53 ` Takashi Iwai [this message]
2020-11-23  8:53 ` [PATCH 27/41] ALSA: usb-audio: Constify audioformat pointer references Takashi Iwai
2020-11-23  8:53 ` [PATCH 28/41] ALSA: usb-audio: Use atomic_t for endpoint use_count Takashi Iwai
2020-11-23  8:53 ` [PATCH 29/41] ALSA: usb-audio: Refactoring endpoint URB deactivation Takashi Iwai
2020-11-23  8:53 ` [PATCH 30/41] ALSA: usb-audio: Drop unneeded snd_usb_substream fields Takashi Iwai
2020-11-23  8:53 ` [PATCH 31/41] ALSA: usb-audio: Unify the code for the next packet size calculation Takashi Iwai
2020-11-23  8:53 ` [PATCH 32/41] ALSA: usb-audio: Simplify rate_min/max and rates set up Takashi Iwai
2020-11-23  8:53 ` [PATCH 33/41] ALSA: usb-audio: Replace slave/master terms Takashi Iwai
2020-11-23  8:53 ` [PATCH 34/41] ALSA: usb-audio: Use unsigned char for iface and altsettings fields Takashi Iwai
2020-11-23  8:53 ` [PATCH 35/41] ALSA: usb-audio: Show sync endpoint information in proc outputs Takashi Iwai
2020-11-23  8:53 ` [PATCH 36/41] ALSA: usb-audio: Quirk for BOSS GT-001 Takashi Iwai
2020-11-23  8:53 ` [PATCH 37/41] ALSA: usb-audio: Factor out the implicit feedback quirk code Takashi Iwai
2020-11-23  8:53 ` [PATCH 38/41] ALSA: usb-audio: Add generic implicit fb parsing Takashi Iwai
2020-11-23  8:53 ` [PATCH 39/41] ALSA: usb-audio: Add implicit_fb module option Takashi Iwai
2020-11-23  9:46   ` Pavel Hofman
2020-11-23  8:53 ` [PATCH 40/41] ALSA: usb-audio: Fix quirks for other BOSS devices Takashi Iwai
2020-11-23  8:53 ` [PATCH 41/41] ALSA: usb-audio: Fix MOTU M-Series quirks Takashi Iwai

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