[PATCH V2] printk: pr_debug_ratelimited: check state first toreduce "callbacks suppressed" messages

From: Joe Perches
Date: Sat Oct 26 2013 - 23:42:06 EST

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

Add #include <linux/dynamic_debug.h> to printk.h. Unfortunately, this
new #include must be after the prototype/declaration of function printk.

It may be better to split out these _ratelimited declarations into
a separate file one day.

Any use of these pr_<foo>_ratelimited functions must also have another
specific #include <ratelimited.h>. Most users have this done indirectly
via #include <linux/kernel.h>

printk.h may not #include <linux/ratelimit.h> as it causes circular
dependencies and compilation failures.

Signed-off-by: Joe Perches <joe@xxxxxxxxxxx>
V2: Fix #include dependencies and typos.

Compile tested with and without CONFIG_DYNAMIC_DEBUG

It looks to me as if device.h should also have #include <dynamic_debug.h>
It currently gets the #include indirectly via kobject.h -> kernel.h.

include/linux/printk.h | 16 +++++++++++++++-
1 file changed, 15 insertions(+), 1 deletion(-)

diff --git a/include/linux/printk.h b/include/linux/printk.h
index e6131a78..6949258 100644
--- a/include/linux/printk.h
+++ b/include/linux/printk.h
@@ -233,6 +233,8 @@ extern asmlinkage void dump_stack(void) __cold;
no_printk(KERN_DEBUG pr_fmt(fmt), ##__VA_ARGS__)

+#include <linux/dynamic_debug.h>
/* If you are writing a driver, please use dev_dbg instead */
/* dynamic_pr_debug() uses pr_fmt() internally so we don't need it here */
@@ -343,7 +345,19 @@ extern asmlinkage void dump_stack(void) __cold;

/* If you are writing a driver, please use dev_dbg instead */
-#if defined(DEBUG)
+/* descriptor check is first to prevent flooding with "callbacks suppressed" */
+#define pr_debug_ratelimited(fmt, ...) \
+do { \
+ if (unlikely(descriptor.flags & _DPRINTK_FLAGS_PRINT) && \
+ __ratelimit(&_rs)) \
+ __dynamic_pr_debug(&descriptor, fmt, ##__VA_ARGS__); \
+} while (0)
+#elif defined(DEBUG)
#define pr_debug_ratelimited(fmt, ...) \
printk_ratelimited(KERN_DEBUG pr_fmt(fmt), ##__VA_ARGS__)

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