linux-kernel - Re: [PATCH] (update) more helpful WARN_ON and BUG

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Date:	Fri, 20 Oct 2006 11:54:10 -0500
From:	Eric Sandeen <sandeen@...deen.net>
To:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] (update) more helpful WARN_ON and BUG_ON messages

Eric Sandeen wrote:

> After a few bugs I encountered in FC6 in buffer.c, with output like:
>
> Kernel BUG at fs/buffer.c: 2791
>
> where buffer.c contains:
>
> ...
>         BUG_ON(!buffer_locked(bh));
>         BUG_ON(!buffer_mapped(bh));
>         BUG_ON(!bh->b_end_io);
> ...
>
> around line 2790, it's awfully tedious to go get the exact failing kernel tree
> just to see -which- BUG_ON was encountered.
>
> Printing out the failing condition as a string would make this more helpful IMHO.
>
> This is mostly just compile-tested... comments?
Whoops, missed WARN_ON_ONCE... thanks Peter.

Signed-off-by: Eric Sandeen <sandeen@...hat.com>

Index: linux-2.6.18/include/asm-generic/bug.h
===================================================================
--- linux-2.6.18.orig/include/asm-generic/bug.h
+++ linux-2.6.18/include/asm-generic/bug.h
@@ -12,13 +12,19 @@
 #endif
 
 #ifndef HAVE_ARCH_BUG_ON
-#define BUG_ON(condition) do { if (unlikely((condition)!=0)) BUG(); } while(0)
+#define BUG_ON(condition) do { \
+	if (unlikely((condition)!=0)) { \
+		printk("BUGging on (%s)\n", #condition); \
+		BUG(); \
+	} \
+} while(0)
 #endif
 
 #ifndef HAVE_ARCH_WARN_ON
 #define WARN_ON(condition) do { \
 	if (unlikely((condition)!=0)) { \
-		printk("BUG: warning at %s:%d/%s()\n", __FILE__, __LINE__, __FUNCTION__); \
+		printk("BUG: warning: (%s) at %s:%d/%s()\n", \
+			#condition, __FILE__, __LINE__, __FUNCTION__); \
 		dump_stack(); \
 	} \
 } while (0)
@@ -45,7 +51,7 @@
 							\
 	if (unlikely((condition) && __warn_once)) {	\
 		__warn_once = 0;			\
-		WARN_ON(1);				\
+		WARN_ON(condition);			\
 		__ret = 1;				\
 	}						\
 	__ret;						\


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