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-rw-r--r--arch/x86_64/lib/rwlock.S38
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 00000000000..0cde1f80731
--- /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)