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

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Date:   Fri, 21 Apr 2023 16:42:57 +0200
From:   Takashi Iwai <tiwai@...e.de>
To:     Chris Down <chris@...isdown.name>
Cc:     linux-kernel@...r.kernel.org, alsa-devel@...a-project.org,
        Jaroslav Kysela <perex@...ex.cz>, Takashi Iwai <tiwai@...e.com>
Subject: Re: [PATCH] usb-audio: Rate limit usb_set_interface error reporting

On Fri, 21 Apr 2023 16:38:41 +0200,
Chris Down wrote:
> 
> 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>

This patch itself is safe and good to have, so I'm going to take it as
is.

But I'm still curious in which code path the problem happens.  That
is, we should address such unnecessary repeats if possible.  Do you
have some more data?


thanks,

Takashi