[PATCH 3.14 89/94] ALSA: usb-audio: Prevent printk ratelimiting from spamming kernel log while DEBUG not defined

From: Greg Kroah-Hartman
Date: Mon Jul 07 2014 - 20:26:17 EST


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

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

From: Sander Eikelenboom <linux@xxxxxxxxxxxxxx>

commit b7a7723513dc89f83d6df13206df55d4dc26e825 upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
sound/usb/pcm.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)

--- a/sound/usb/pcm.c
+++ b/sound/usb/pcm.c
@@ -1487,9 +1487,9 @@ static void retire_playback_urb(struct s
* 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)
- snd_printk(KERN_DEBUG "delay: estimated %d, actual %d\n",
+ 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);

if (!subs->running) {


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