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authorAndi Kleen <ak@suse.de>2006-09-26 10:52:28 +0200
committerAndi Kleen <andi@basil.nowhere.org>2006-09-26 10:52:28 +0200
commit9a0b26e6bc4ae1979d9bcc6194e57a71b2b5cac6 (patch)
tree01601a502007b85d4fc88f79de7a93c257ef9d97 /include/asm-x86_64
parentb4062b16094038334d9bbadac0397a3fc9e981b0 (diff)
downloadop-kernel-dev-9a0b26e6bc4ae1979d9bcc6194e57a71b2b5cac6.zip
op-kernel-dev-9a0b26e6bc4ae1979d9bcc6194e57a71b2b5cac6.tar.gz
[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>
Diffstat (limited to 'include/asm-x86_64')
-rw-r--r--include/asm-x86_64/rwlock.h68
-rw-r--r--include/asm-x86_64/spinlock.h11
2 files changed, 12 insertions, 67 deletions
diff --git a/include/asm-x86_64/rwlock.h b/include/asm-x86_64/rwlock.h
index dea0e94..28a080d 100644
--- a/include/asm-x86_64/rwlock.h
+++ b/include/asm-x86_64/rwlock.h
@@ -18,69 +18,21 @@
#ifndef _ASM_X86_64_RWLOCK_H
#define _ASM_X86_64_RWLOCK_H
-#include <linux/stringify.h>
-
#define RW_LOCK_BIAS 0x01000000
-#define RW_LOCK_BIAS_STR "0x01000000"
+#define RW_LOCK_BIAS_STR "0x01000000"
-#define __build_read_lock_ptr(rw, helper) \
+#define __build_read_lock(rw) \
asm volatile(LOCK_PREFIX "subl $1,(%0)\n\t" \
- "js 2f\n" \
- "1:\n" \
- LOCK_SECTION_START("") \
- "2:\tcall " helper "\n\t" \
- "jmp 1b\n" \
- LOCK_SECTION_END \
- ::"a" (rw) : "memory")
-
-#define __build_read_lock_const(rw, helper) \
- asm volatile(LOCK_PREFIX "subl $1,%0\n\t" \
- "js 2f\n" \
+ "jns 1f\n" \
+ "call __read_lock_failed\n" \
"1:\n" \
- LOCK_SECTION_START("") \
- "2:\tpushq %%rax\n\t" \
- "leaq %0,%%rax\n\t" \
- "call " helper "\n\t" \
- "popq %%rax\n\t" \
- "jmp 1b\n" \
- LOCK_SECTION_END \
- :"=m" (*((volatile int *)rw))::"memory")
-
-#define __build_read_lock(rw, helper) do { \
- if (__builtin_constant_p(rw)) \
- __build_read_lock_const(rw, helper); \
- else \
- __build_read_lock_ptr(rw, helper); \
- } while (0)
+ ::"D" (rw), "i" (RW_LOCK_BIAS) : "memory")
-#define __build_write_lock_ptr(rw, helper) \
- asm volatile(LOCK_PREFIX "subl $" RW_LOCK_BIAS_STR ",(%0)\n\t" \
- "jnz 2f\n" \
+#define __build_write_lock(rw) \
+ asm volatile(LOCK_PREFIX "subl %1,(%0)\n\t" \
+ "jz 1f\n" \
+ "\tcall __write_lock_failed\n\t" \
"1:\n" \
- LOCK_SECTION_START("") \
- "2:\tcall " helper "\n\t" \
- "jmp 1b\n" \
- LOCK_SECTION_END \
- ::"a" (rw) : "memory")
-
-#define __build_write_lock_const(rw, helper) \
- asm volatile(LOCK_PREFIX "subl $" RW_LOCK_BIAS_STR ",%0\n\t" \
- "jnz 2f\n" \
- "1:\n" \
- LOCK_SECTION_START("") \
- "2:\tpushq %%rax\n\t" \
- "leaq %0,%%rax\n\t" \
- "call " helper "\n\t" \
- "popq %%rax\n\t" \
- "jmp 1b\n" \
- LOCK_SECTION_END \
- :"=m" (*((volatile long *)rw))::"memory")
-
-#define __build_write_lock(rw, helper) do { \
- if (__builtin_constant_p(rw)) \
- __build_write_lock_const(rw, helper); \
- else \
- __build_write_lock_ptr(rw, helper); \
- } while (0)
+ ::"D" (rw), "i" (RW_LOCK_BIAS) : "memory")
#endif
diff --git a/include/asm-x86_64/spinlock.h b/include/asm-x86_64/spinlock.h
index 248a79f..a8e3d89 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)
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