ratelimit: Make suppressed output messages more useful

Today I got:

  [39648.224782] Registered led device: iwl-phy0::TX
  [40676.545099] __ratelimit: 246 callbacks suppressed
  [40676.545103] abcdef[23675]: segfault at 0 ...

as you can see the ratelimit message contains a function prefix.
Since this is always __ratelimit, this wont help much.

This patch changes __ratelimit and printk_ratelimit to print the
function name that calls ratelimit.

This will pinpoint the responsible function, as long as not several
different places call ratelimit with the same ratelimit state at
the same time. In that case we catch only one random function that
calls ratelimit after the wait period.

Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: Dave Young <hidave.darkstar@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
CC: Andrew Morton <akpm@linux-foundation.org>
LKML-Reference: <200910231458.11832.borntraeger@de.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

include/linux/kernel.h

@@ -240,7 +240,8 @@ asmlinkage int vprintk(const char *fmt, va_list args)
 asmlinkage int printk(const char * fmt, ...)
 	__attribute__ ((format (printf, 1, 2))) __cold;
 
-extern int printk_ratelimit(void);
+extern int __printk_ratelimit(const char *func);
+#define printk_ratelimit() __printk_ratelimit(__func__)
 extern bool printk_timed_ratelimit(unsigned long *caller_jiffies,
 				   unsigned int interval_msec);
 

include/linux/ratelimit.h

@@ -25,6 +25,7 @@ struct ratelimit_state {
 		.burst		= burst_init,				\
 	}
 
-extern int __ratelimit(struct ratelimit_state *rs);
+extern int ___ratelimit(struct ratelimit_state *rs, const char *func);
+#define __ratelimit(state) ___ratelimit(state, __func__)
 
 #endif /* _LINUX_RATELIMIT_H */

kernel/printk.c

@@ -1364,11 +1364,11 @@ late_initcall(disable_boot_consoles);
  */
 DEFINE_RATELIMIT_STATE(printk_ratelimit_state, 5 * HZ, 10);
 
-int printk_ratelimit(void)
+int __printk_ratelimit(const char *func)
 {
-	return __ratelimit(&printk_ratelimit_state);
+	return ___ratelimit(&printk_ratelimit_state, func);
 }
-EXPORT_SYMBOL(printk_ratelimit);
+EXPORT_SYMBOL(__printk_ratelimit);
 
 /**
  * printk_timed_ratelimit - caller-controlled printk ratelimiting

lib/ratelimit.c

@@ -20,7 +20,7 @@
  * This enforces a rate limit: not more than @rs->ratelimit_burst callbacks
  * in every @rs->ratelimit_jiffies
  */
-int __ratelimit(struct ratelimit_state *rs)
+int ___ratelimit(struct ratelimit_state *rs, const char *func)
 {
 	unsigned long flags;
 	int ret;
@@ -43,7 +43,7 @@ int __ratelimit(struct ratelimit_state *rs)
 	if (time_is_before_jiffies(rs->begin + rs->interval)) {
 		if (rs->missed)
 			printk(KERN_WARNING "%s: %d callbacks suppressed\n",
-				__func__, rs->missed);
+				func, rs->missed);
 		rs->begin   = 0;
 		rs->printed = 0;
 		rs->missed  = 0;
@@ -59,4 +59,4 @@ int __ratelimit(struct ratelimit_state *rs)
 
 	return ret;
 }
-EXPORT_SYMBOL(__ratelimit);
+EXPORT_SYMBOL(___ratelimit);