* Linus Torvalds <[EMAIL PROTECTED]> wrote:
> > +static inline int read_can_lock(rwlock_t *rw)
> > +{
> > + return rw->lock > 0;
> > +}
>
> No, it does need the cast to signed, otherwise it will return true for
> the case where somebody holds the write-lock _and_ there's a pending
> reader waiting too (the write-lock will make it zero, the pending
> reader will wrap around and make it negative, but since "lock" is
> "unsigned", it will look like a large value to "read_can_lock".
indeed. Another solution would be to make the type signed - patch below.
(like ppc64 does)
> I also think I'd prefer to do the things as macros, and do the
> type-safety by just renaming the "lock" field like Chris did. [...]
(i sent the original lock/slock renaming patch yesterday, and i think
Chris simply reworked&resent that one.)
Ingo
--- linux/include/asm-i386/spinlock.h.orig
+++ linux/include/asm-i386/spinlock.h
@@ -179,7 +179,7 @@ static inline void _raw_spin_lock_flags
* read-locks.
*/
typedef struct {
- volatile unsigned int lock;
+ volatile signed int lock;
#ifdef CONFIG_DEBUG_SPINLOCK
unsigned magic;
#endif
-
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