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

From: Petr Vandrovec <vandrove@vc.cvut.cz>

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.

The problem is that these spinlocks first print warning, and then
decrement babble.  So if the lock is used by printk code (like runqueue
lock was), we get nothing, just a lockup or a double fault...  When we
first decrement babble and then print the error message we can break
this unfortunate situation and the error message (5 of the same...)
appear on screen.

include/linux/spinlock.h

@@ -79,10 +79,10 @@ typedef struct {
 	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 @@ typedef struct {
 	({ \
 	 	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 @@ typedef struct {
 	({ \
 	 	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 @@ typedef struct {
 	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 @@ typedef struct {
 	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)