printk: pr_debug_ratelimited: check state first to reduce "callbacks suppressed" messages

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@perches.com>
Tested-by: Krzysztof Mazur <krzysiek@podlesie.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 15 insertions, 1 deletions

diff --git a/include/linux/printk.h b/include/linux/printk.h
index e6131a782481..694925837a16 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__)
 #endif
 
+#include <linux/dynamic_debug.h>
+
 /* If you are writing a driver, please use dev_dbg instead */
 #if defined(CONFIG_DYNAMIC_DEBUG)
 /* 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;
 #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(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(&descriptor, fmt, ##__VA_ARGS__);    \
+} while (0)
+#elif defined(DEBUG)
 #define pr_debug_ratelimited(fmt, ...)                                  \
         printk_ratelimited(KERN_DEBUG pr_fmt(fmt), ##__VA_ARGS__)
 #else