[PATCH] Make debugging variant of spinlocks a bit more robust

[PATCH] Make debugging variant of spinlocks a bit more robust

[Petr Vandrovec]

Hi,
  While I was trying to hunt down problem with spin_lock_irq
in send_sig_info, I noticed that debugging spinlocks are a bit
unusable.

  Problem is that these spinlocks first print warning, and
then decrement babble. So if lock is used by printk code (like
runqueue lock was), we get nothing, just lockup or double fault...
When we first decrement babble and then printing error message
we can break this unfortunate situation and error message
(5 same error messages...) appear on screen.
					Thanks,
						Petr Vandrovec
						vandrove@vc.cvut.cz


diff -urdN linux/include/linux/spinlock.h linux/include/linux/spinlock.h
--- linux/include/linux/spinlock.h	2003-05-09 04:35:34.000000000 +0200
+++ linux/include/linux/spinlock.h	2003-05-09 22:12:21.000000000 +0200
@@ -79,10 +79,10 @@
 	do { \
 	 	CHECK_LOCK(x); \
 		if ((x)->lock&&(x)->babble) { \
+			(x)->babble--; \
 			printk("%s:%d: spin_lock(%s:%p) already locked by %s/%d\n", \
 					__FILE__,__LINE__, (x)->module, \
 					(x), (x)->owner, (x)->oline); \
-			(x)->babble--; \
 		} \
 		(x)->lock = 1; \
 		(x)->owner = __FILE__; \
@@ -95,10 +95,10 @@
 	({ \
 	 	CHECK_LOCK(x); \
 		if ((x)->lock&&(x)->babble) { \
+			(x)->babble--; \
 			printk("%s:%d: spin_is_locked(%s:%p) already locked by %s/%d\n", \
 					__FILE__,__LINE__, (x)->module, \
 					(x), (x)->owner, (x)->oline); \
-			(x)->babble--; \
 		} \
 		0; \
 	})
@@ -109,10 +109,10 @@
 	({ \
 	 	CHECK_LOCK(x); \
 		if ((x)->lock&&(x)->babble) { \
+			(x)->babble--; \
 			printk("%s:%d: spin_trylock(%s:%p) already locked by %s/%d\n", \
 					__FILE__,__LINE__, (x)->module, \
 					(x), (x)->owner, (x)->oline); \
-			(x)->babble--; \
 		} \
 		(x)->lock = 1; \
 		(x)->owner = __FILE__; \
@@ -124,10 +124,10 @@
 	do { \
 	 	CHECK_LOCK(x); \
 		if ((x)->lock&&(x)->babble) { \
+			(x)->babble--; \
 			printk("%s:%d: spin_unlock_wait(%s:%p) owned by %s/%d\n", \
 					__FILE__,__LINE__, (x)->module, (x), \
 					(x)->owner, (x)->oline); \
-			(x)->babble--; \
 		}\
 	} while (0)
 
@@ -135,9 +135,9 @@
 	do { \
 	 	CHECK_LOCK(x); \
 		if (!(x)->lock&&(x)->babble) { \
+			(x)->babble--; \
 			printk("%s:%d: spin_unlock(%s:%p) not locked\n", \
 					__FILE__,__LINE__, (x)->module, (x));\
-			(x)->babble--; \
 		} \
 		(x)->lock = 0; \
 	} while (0)