[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>

3 files changed, 39 insertions, 31 deletions

diff --git a/arch/x86_64/lib/Makefile b/arch/x86_64/lib/Makefile
index ccef6ae747a3..b78d4170fce2 100644
--- a/arch/x86_64/lib/Makefile
+++ b/arch/x86_64/lib/Makefile
@@ -9,4 +9,4 @@ obj-y := io.o iomap_copy.o
 lib-y := csum-partial.o csum-copy.o csum-wrappers.o delay.o \
         usercopy.o getuser.o putuser.o  \
         thunk.o clear_page.o copy_page.o bitstr.o bitops.o
-lib-y += memcpy.o memmove.o memset.o copy_user.o
+lib-y += memcpy.o memmove.o memset.o copy_user.o rwlock.o
diff --git a/arch/x86_64/lib/rwlock.S b/arch/x86_64/lib/rwlock.S
new file mode 100644
index 000000000000..0cde1f807314
--- /dev/null
+++ b/arch/x86_64/lib/rwlock.S
@@ -0,0 +1,38 @@
+/* Slow paths of read/write spinlocks. */
+
+#include <linux/linkage.h>
+#include <asm/rwlock.h>
+#include <asm/alternative-asm.i>
+#include <asm/dwarf2.h>
+
+/* rdi: pointer to rwlock_t */
+ENTRY(__write_lock_failed)
+        CFI_STARTPROC
+        LOCK_PREFIX
+        addl $RW_LOCK_BIAS,(%rdi)
+1:      rep
+        nop
+        cmpl $RW_LOCK_BIAS,(%rdi)
+        jne 1b
+        LOCK_PREFIX
+        subl $RW_LOCK_BIAS,(%rdi)
+        jnz  __write_lock_failed
+        ret
+        CFI_ENDPROC
+END(__write_lock_failed)
+
+/* rdi: pointer to rwlock_t */
+ENTRY(__read_lock_failed)
+        CFI_STARTPROC
+        LOCK_PREFIX
+        incl (%rdi)
+1:      rep
+        nop
+        cmpl $1,(%rdi)
+        js 1b
+        LOCK_PREFIX
+        decl (%rdi)
+        js __read_lock_failed
+        ret
+        CFI_ENDPROC
+END(__read_lock_failed)
diff --git a/arch/x86_64/lib/thunk.S b/arch/x86_64/lib/thunk.S
index 332ea5dff916..6cff27c775ae 100644
--- a/arch/x86_64/lib/thunk.S
+++ b/arch/x86_64/lib/thunk.S
@@ -67,33 +67,3 @@ restore_norax:
         RESTORE_ARGS 1
         ret
         CFI_ENDPROC
-
-#ifdef CONFIG_SMP
-/* Support for read/write spinlocks. */
-        .text
-/* rax: pointer to rwlock_t */  
-ENTRY(__write_lock_failed)
-        lock
-        addl $RW_LOCK_BIAS,(%rax)
-1:      rep
-        nop
-        cmpl $RW_LOCK_BIAS,(%rax)
-        jne 1b
-        lock 
-        subl $RW_LOCK_BIAS,(%rax)
-        jnz  __write_lock_failed
-        ret
-
-/* rax: pointer to rwlock_t */  
-ENTRY(__read_lock_failed)
-        lock
-        incl (%rax)
-1:      rep
-        nop
-        cmpl $1,(%rax)
-        js 1b
-        lock
-        decl (%rax)
-        js __read_lock_failed
-        ret
-#endif