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.
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.
25-akpm/include/linux/spinlock.h | 10 +++++-----
1 files changed, 5 insertions(+), 5 deletions(-)
diff -puN include/linux/spinlock.h~spinlock-debugging-improvement include/linux/spinlock.h
--- 25/include/linux/spinlock.h~spinlock-debugging-improvement Fri May 9 18:03:49 2003
+++ 25-akpm/include/linux/spinlock.h Fri May 9 18:03:49 2003
@@ -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)
_