linux-kernel - [PATCH 3.13 002/198] ALSA: usb-audio: Prevent printk ratelimiting from spamming kernel log while DEBUG not defined

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Date:	Tue, 15 Jul 2014 14:27:52 -0700
From:	Kamal Mostafa <kamal@...onical.com>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	kernel-team@...ts.ubuntu.com
Cc:	Sander Eikelenboom <linux@...elenboom.it>,
	Takashi Iwai <tiwai@...e.de>,
	Joseph Salisbury <joseph.salisbury@...onical.com>,
	Kamal Mostafa <kamal@...onical.com>
Subject: [PATCH 3.13 002/198] ALSA: usb-audio: Prevent printk ratelimiting from spamming kernel log while DEBUG not defined

3.13.11.5 -stable review patch.  If anyone has any objections, please let me know.

------------------

From: Sander Eikelenboom <linux@...elenboom.it>

commit b7a7723513dc89f83d6df13206df55d4dc26e825 upstream.

BugLink: http://bugs.launchpad.net/bugs/1319457

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>
Signed-off-by: Takashi Iwai <tiwai@...e.de>
(backported from commit b7a7723513dc89f83d6df13206df55d4dc26e825)
Signed-off-by: Joseph Salisbury <joseph.salisbury@...onical.com>
Signed-off-by: Kamal Mostafa <kamal@...onical.com>
---
 sound/usb/pcm.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/sound/usb/pcm.c b/sound/usb/pcm.c
index ca3256d..ede4b92 100644
--- a/sound/usb/pcm.c
+++ b/sound/usb/pcm.c
@@ -1488,7 +1488,8 @@ static void retire_playback_urb(struct snd_usb_substream *subs,
 	 * on two reads of a counter updated every ms.
 	 */
 	if (abs(est_delay - subs->last_delay) * 1000 > runtime->rate * 2)
-		snd_printk(KERN_DEBUG "delay: estimated %d, actual %d\n",
+		dev_dbg_ratelimited(&subs->dev->dev,
+			"delay: estimated %d, actual %d\n",
 			est_delay, subs->last_delay);
 
 	if (!subs->running) {
-- 
1.9.1

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