1 files changed, 44 insertions, 0 deletions

diff --git a/arch/x86/lib/rwlock.S b/arch/x86/lib/rwlock.S
new file mode 100644
index 000000000000..fca17829caa8
--- /dev/null
+++ b/arch/x86/lib/rwlock.S
@@ -0,0 +1,44 @@
+/* Slow paths of read/write spinlocks. */
+
+#include <linux/linkage.h>
+#include <asm/alternative-asm.h>
+#include <asm/frame.h>
+#include <asm/rwlock.h>
+
+#ifdef CONFIG_X86_32
+# define __lock_ptr eax
+#else
+# define __lock_ptr rdi
+#endif
+
+ENTRY(__write_lock_failed)
+        CFI_STARTPROC
+        FRAME
+0:      LOCK_PREFIX
+        addl    $RW_LOCK_BIAS, (%__lock_ptr)
+1:      rep; nop
+        cmpl    $RW_LOCK_BIAS, (%__lock_ptr)
+        jne     1b
+        LOCK_PREFIX
+        subl    $RW_LOCK_BIAS, (%__lock_ptr)
+        jnz     0b
+        ENDFRAME
+        ret
+        CFI_ENDPROC
+END(__write_lock_failed)
+
+ENTRY(__read_lock_failed)
+        CFI_STARTPROC
+        FRAME
+0:      LOCK_PREFIX
+        incl    (%__lock_ptr)
+1:      rep; nop
+        cmpl    $1, (%__lock_ptr)
+        js      1b
+        LOCK_PREFIX
+        decl    (%__lock_ptr)
+        js      0b
+        ENDFRAME
+        ret
+        CFI_ENDPROC
+END(__read_lock_failed)