[v3.10.y][v3.11.y][v3.12.y][v3.13.y][v3.14.y][PATCH 1/1][V2] ALSA: usb-audio: Prevent printk ratelimiting from spamming kernel log while DEBUG not defined

From: Joseph Salisbury
Date: Wed Jun 18 2014 - 14:32:43 EST


From: Sander Eikelenboom <linux@xxxxxxxxxxxxxx>

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@xxxxxxxxxxxxxx>
Signed-off-by: Takashi Iwai <tiwai@xxxxxxx>
(backported from commit b7a7723513dc89f83d6df13206df55d4dc26e825)
Signed-off-by: Joseph Salisbury <joseph.salisbury@xxxxxxxxxxxxx>
---
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) {
--
2.0.0

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