[PATCH] Clean up read write lock assembly

- Move the slow path fallbacks to their own assembly files
This makes them much easier to read and is needed for the next change.
- Add CFI annotations for unwinding (XXX need review)
- Remove constant case which can never happen with out of line spinlocks
- Use patchable LOCK prefixes
- Don't use lock sections anymore for inline code because they can't
be expressed by the unwinder (this adds one taken jump to the lock
fast path)

Cc: jbeulich@novell.com

Signed-off-by: Andi Kleen <ak@suse.de>

1 files changed, 2 insertions, 9 deletions

diff --git a/include/asm-x86_64/spinlock.h b/include/asm-x86_64/spinlock.h
index 248a79f0eaff..a8e3d89f591f 100644
--- a/include/asm-x86_64/spinlock.h
+++ b/include/asm-x86_64/spinlock.h
@@ -79,13 +79,6 @@ static inline void __raw_spin_unlock(raw_spinlock_t *lock)
  *
  * On x86, we implement read-write locks as a 32-bit counter
  * with the high bit (sign) being the "contended" bit.
- *
- * The inline assembly is non-obvious. Think about it.
- *
- * Changed to use the same technique as rw semaphores.  See
- * semaphore.h for details.  -ben
- *
- * the helpers are in arch/i386/kernel/semaphore.c
  */
 
 #define __raw_read_can_lock(x)          ((int)(x)->lock > 0)
@@ -93,12 +86,12 @@ static inline void __raw_spin_unlock(raw_spinlock_t *lock)
 
 static inline void __raw_read_lock(raw_rwlock_t *rw)
 {
-        __build_read_lock(rw, "__read_lock_failed");
+        __build_read_lock(rw);
 }
 
 static inline void __raw_write_lock(raw_rwlock_t *rw)
 {
-        __build_write_lock(rw, "__write_lock_failed");
+        __build_write_lock(rw);
 }
 
 static inline int __raw_read_trylock(raw_rwlock_t *lock)