linux-kernel - [PATCH] usb-audio: Rate limit usb_set

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Date:   Fri, 21 Apr 2023 15:38:41 +0100
From:   Chris Down <chris@...isdown.name>
To:     linux-kernel@...r.kernel.org
Cc:     alsa-devel@...a-project.org, Jaroslav Kysela <perex@...ex.cz>,
        Takashi Iwai <tiwai@...e.com>
Subject: [PATCH] usb-audio: Rate limit usb_set_interface error reporting

When an error occurs during USB disconnection sometimes things can go
wrong as endpoint_set_interface may end up being called repeatedly. For
example:

% dmesg --notime | grep 'usb 3-7.1.4' | sort | uniq -c | head -2
   3069 usb 3-7.1.4: 1:1: usb_set_interface failed (-19)
    908 usb 3-7.1.4: 1:1: usb_set_interface failed (-71)

In my case, there sometimes are hundreds of these usb_set_interface
failure messages a second when I disconnect the hub that has my USB
audio device.

These messages can take a huge amount of the kmsg ringbuffer and don't
provide any extra information over the previous ones, so ratelimit them.

Signed-off-by: Chris Down <chris@...isdown.name>
---
 sound/usb/endpoint.c | 5 +++--
 sound/usb/usbaudio.h | 2 ++
 2 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/sound/usb/endpoint.c b/sound/usb/endpoint.c
index 647fa054d8b1..2cd99cc8c360 100644
--- a/sound/usb/endpoint.c
+++ b/sound/usb/endpoint.c
@@ -916,8 +916,9 @@ static int endpoint_set_interface(struct snd_usb_audio *chip,
 		      ep->iface, altset, ep->ep_num);
 	err = usb_set_interface(chip->dev, ep->iface, altset);
 	if (err < 0) {
-		usb_audio_err(chip, "%d:%d: usb_set_interface failed (%d)\n",
-			      ep->iface, altset, err);
+		usb_audio_err_ratelimited(
+			chip, "%d:%d: usb_set_interface failed (%d)\n",
+			ep->iface, altset, err);
 		return err;
 	}
 
diff --git a/sound/usb/usbaudio.h b/sound/usb/usbaudio.h
index f5a8dca66457..38a85b2c9a73 100644
--- a/sound/usb/usbaudio.h
+++ b/sound/usb/usbaudio.h
@@ -67,6 +67,8 @@ struct snd_usb_audio {
 
 #define usb_audio_err(chip, fmt, args...) \
 	dev_err(&(chip)->dev->dev, fmt, ##args)
+#define usb_audio_err_ratelimited(chip, fmt, args...) \
+	dev_err_ratelimited(&(chip)->dev->dev, fmt, ##args)
 #define usb_audio_warn(chip, fmt, args...) \
 	dev_warn(&(chip)->dev->dev, fmt, ##args)
 #define usb_audio_info(chip, fmt, args...) \
-- 
2.40.0