linux-kernel - [PATCH] printk: pr_debug_ratelimited: check state first to reduce "callbacks suppressed" messages

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Date:	Sat, 26 Oct 2013 11:52:02 -0700
From:	Joe Perches <joe@...ches.com>
To:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Jason Baron <jbaron@...mai.com>,
	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Krzysztof Mazur <krzysiek@...lesie.net>,
	Felipe Balbi <balbi@...com>, linux-kernel@...r.kernel.org,
	linux-usb@...r.kernel.org
Subject: [PATCH] printk: pr_debug_ratelimited: check state first to reduce
 "callbacks suppressed" messages

pr_debug_ratelimited should be coded similar to dev_dbg_ratelimited
to reduce the "callbacks suppressed" messages.

Signed-off-by: Joe Perches <joe@...ches.com>
---
On Sat, 2013-10-26 at 18:37 +0100, Greg Kroah-Hartman wrote:
> On Sat, Oct 26, 2013 at 03:29:56PM +0200, Krzysztof Mazur wrote:
> > Hi,
> > 
> > commit 2d6401cf4ca3861692a4779745e0049cac769d10
> > ("USB: usbatm: move the atm_dbg() call to use dynamic debug")
> > changed the atm_rldbg() to:
> > 
> > #define atm_rldbg(instance, format, arg...)		\
> > 	if (printk_ratelimit())				\
> > 		atm_dbg(instance , format , ## arg)
> > 
> > and now printk_ratelimit() is always called even when debugging is
> > disabled and a lot of "callbacks suppressed" messages are printed
> > by the printk_ratelimit():
> > 
> > [...]
> > usbatm_rx_process: 4977 callbacks suppressed
> > usbatm_extract_one_cell: 2920 callbacks suppressed
> > [...]
> > 
> > 
> > I'm not sure how to fix that, maybe we need dynamic_pr_debug_ratelimit()?
> 
> How about just deleting the use of that macro entirely?  Odds are it's
> not really needed anymore, right?

 include/linux/printk.h | 14 +++++++++++++-
 1 file changed, 13 insertions(+), 1 deletion(-)

diff --git a/include/linux/printk.h b/include/linux/printk.h
index e6131a78..449d924 100644
--- a/include/linux/printk.h
+++ b/include/linux/printk.h
@@ -343,7 +343,19 @@ extern asmlinkage void dump_stack(void) __cold;
 #endif
 
 /* If you are writing a driver, please use dev_dbg instead */
-#if defined(DEBUG)
+#if defined(CONFIG_DYNAMIC_DEBUG)
+/* descriptor check is first to prevent flooding with "callbacks suppressed" */
+#define pr_debug_ratelimited(dev, fmt, ...)				\
+do {									\
+	static DEFINE_RATELIMIT_STATE(_rs,				\
+				      DEFAULT_RATELIMIT_INTERVAL,	\
+				      DEFAULT_RATELIMIT_BURST);		\
+	DEFINE_DYNAMIC_DEBUG_METADATA(descriptor, fmt);			\
+	if (unlikely(descriptor.flags & _DPRINTK_FLAGS_PRINT) &&	\
+	    __ratelimit(&_rs))						\
+		__dynamic_pr_debug(fmt, ##__VA_ARGS__);			\
+} while (0)
+#elif defined(DEBUG)
 #define pr_debug_ratelimited(fmt, ...)					\
 	printk_ratelimited(KERN_DEBUG pr_fmt(fmt), ##__VA_ARGS__)
 #else


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