1 files changed, 38 insertions, 0 deletions

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)