[prev in list] [next in list] [prev in thread] [next in thread] 

List:       linux-sound
Subject:    Re: [PATCH] Sound USB: Prevent printk ratelimiting from spamming kernel log while DEBUG not defined
From:       Sander Eikelenboom <linux () eikelenboom ! it>
Date:       2014-05-02 16:25:30
Message-ID: 80394451.20140502182530 () eikelenboom ! it
[Download RAW message or body]


Friday, May 2, 2014, 6:13:09 PM, you wrote:

> At Fri,  2 May 2014 15:09:27 +0200,
> Sander Eikelenboom wrote:
> > 
> > This (widely used) construction:
> > 
> > if(printk_ratelimit())
> > dev_dbg()
> > 
> > Causes the ratelimiting to spam the kernel log with the "callbacks suppressed"
> > message below, even while the dev_dbg it is supposed to rate limit wouldn't
> > print anything because DEBUG is not defined for this device.
> > 
> > [  533.803964] retire_playback_urb: 852 callbacks suppressed
> > [  538.807930] retire_playback_urb: 852 callbacks suppressed
> > [  543.811897] retire_playback_urb: 852 callbacks suppressed
> > [  548.815745] retire_playback_urb: 852 callbacks suppressed
> > [  553.819826] retire_playback_urb: 852 callbacks suppressed
> > 
> > So use dev_dbg_ratelimited() instead of this construction.
> > 
> > Signed-off-by: Sander Eikelenboom <linux@eikelenboom.it>

> Thanks, applied.  This is a result of the recent rewrite to dev_dbg()
> from plain printk(), I suppose.

Yes that patch (https://lkml.org/lkml/2014/4/9/457) prevented spamming the kernel log \
when debugging was enabled .. but  now the rate limiting code starts spamming the \
kernel log instead :-)

I must say i wasn't very aware of that effect either and also used this construction \
on  debug patches.


> Takashi

> > ---
> > sound/usb/pcm.c |    5 ++---
> > 1 file changed, 2 insertions(+), 3 deletions(-)
> > 
> > diff --git a/sound/usb/pcm.c b/sound/usb/pcm.c
> > index 131336d..c62a165 100644
> > --- a/sound/usb/pcm.c
> > +++ b/sound/usb/pcm.c
> > @@ -1501,9 +1501,8 @@ static void retire_playback_urb(struct snd_usb_substream \
> >                 *subs,
> > * The error should be lower than 2ms since the estimate relies
> > * on two reads of a counter updated every ms.
> > */
> > -     if (printk_ratelimit() &&
> > -         abs(est_delay - subs->last_delay) * 1000 > runtime->rate * 2)
> > -             dev_dbg(&subs->dev->dev,
> > +     if (abs(est_delay - subs->last_delay) * 1000 > runtime->rate * 2)
> > +             dev_dbg_ratelimited(&subs->dev->dev,
> > "delay: estimated %d, actual %d\n",
> > est_delay, subs->last_delay);
> > 
> > -- 
> > 1.7.10.4
> > 


--
To unsubscribe from this list: send the line "unsubscribe linux-sound" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html


[prev in list] [next in list] [prev in thread] [next in thread]