linux-kernel - [PATCH] Sound USB: Prevent printk ratelimiting from spamming kernel log while DEBUG not defined

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Message-Id: <1399036167-6203-2-git-send-email-linux@eikelenboom.it>
Date:	Fri,  2 May 2014 15:09:27 +0200
From:	Sander Eikelenboom <linux@...elenboom.it>
To:	Takashi Iwai <tiwai@...e.de>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Julia Lawall <julia.lawall@...6.fr>
Cc:	Sander Eikelenboom <linux@...elenboom.it>,
	linux-sound@...r.kernel.org,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: [PATCH] Sound USB: Prevent printk ratelimiting from spamming kernel log while DEBUG not defined

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@...elenboom.it>
---
 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

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