Merge branch 'x86-rwsem-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip

* 'x86-rwsem-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip:
  x86-64, rwsem: Avoid store forwarding hazard in __downgrade_write
  x86-64, rwsem: 64-bit xadd rwsem implementation
  x86: Fix breakage of UML from the changes in the rwsem system
  x86-64: support native xadd rwsem implementation
  x86: clean up rwsem type system

1 files changed, 81 insertions, 0 deletions

diff --git a/arch/x86/lib/rwsem_64.S b/arch/x86/lib/rwsem_64.S
new file mode 100644
index 00000000000..15acecf0d7a
--- /dev/null
+++ b/arch/x86/lib/rwsem_64.S
@@ -0,0 +1,81 @@
+/*
+ * x86-64 rwsem wrappers
+ *
+ * This interfaces the inline asm code to the slow-path
+ * C routines. We need to save the call-clobbered regs
+ * that the asm does not mark as clobbered, and move the
+ * argument from %rax to %rdi.
+ *
+ * NOTE! We don't need to save %rax, because the functions
+ * will always return the semaphore pointer in %rax (which
+ * is also the input argument to these helpers)
+ *
+ * The following can clobber %rdx because the asm clobbers it:
+ *   call_rwsem_down_write_failed
+ *   call_rwsem_wake
+ * but %rdi, %rsi, %rcx, %r8-r11 always need saving.
+ */
+
+#include <linux/linkage.h>
+#include <asm/rwlock.h>
+#include <asm/alternative-asm.h>
+#include <asm/frame.h>
+#include <asm/dwarf2.h>
+
+#define save_common_regs \
+	pushq %rdi; \
+	pushq %rsi; \
+	pushq %rcx; \
+	pushq %r8; \
+	pushq %r9; \
+	pushq %r10; \
+	pushq %r11
+
+#define restore_common_regs \
+	popq %r11; \
+	popq %r10; \
+	popq %r9; \
+	popq %r8; \
+	popq %rcx; \
+	popq %rsi; \
+	popq %rdi
+
+/* Fix up special calling conventions */
+ENTRY(call_rwsem_down_read_failed)
+	save_common_regs
+	pushq %rdx
+	movq %rax,%rdi
+	call rwsem_down_read_failed
+	popq %rdx
+	restore_common_regs
+	ret
+	ENDPROC(call_rwsem_down_read_failed)
+
+ENTRY(call_rwsem_down_write_failed)
+	save_common_regs
+	movq %rax,%rdi
+	call rwsem_down_write_failed
+	restore_common_regs
+	ret
+	ENDPROC(call_rwsem_down_write_failed)
+
+ENTRY(call_rwsem_wake)
+	decw %dx    /* do nothing if still outstanding active readers */
+	jnz 1f
+	save_common_regs
+	movq %rax,%rdi
+	call rwsem_wake
+	restore_common_regs
+1:	ret
+	ENDPROC(call_rwsem_wake)
+
+/* Fix up special calling conventions */
+ENTRY(call_rwsem_downgrade_wake)
+	save_common_regs
+	pushq %rdx
+	movq %rax,%rdi
+	call rwsem_downgrade_wake
+	popq %rdx
+	restore_common_regs
+	ret
+	ENDPROC(call_rwsem_downgrade_wake)