Enter mtx_enter_try. In part for completeness, things may start

using this soon(ish).  Ok oga@, sorta yes kettenis@.

1 files changed, 43 insertions, 2 deletions

diff --git a/sys/arch/amd64/amd64/mutex.S b/sys/arch/amd64/amd64/mutex.S
index 17905d3bc5e..d74669e9a4b 100644
--- a/sys/arch/amd64/amd64/mutex.S
+++ b/sys/arch/amd64/amd64/mutex.S
@@ -1,4 +1,4 @@
-/*	$OpenBSD: mutex.S,v 1.4 2005/07/26 08:11:11 art Exp $	*/
+/*	$OpenBSD: mutex.S,v 1.5 2009/04/25 20:14:42 weingart Exp $	*/
 
 /*
  * Copyright (c) 2004 Artur Grabowski <art@openbsd.org>
@@ -84,7 +84,48 @@ ENTRY(mtx_enter)
 	call	_C_LABEL(panic)
 5:	.asciz	"mtx_enter: locking against myself"
 #endif
-	
+
+ENTRY(mtx_enter_try)
+1:	movl	MTX_WANTIPL(%rdi), %eax
+	movq	CPUVAR(SELF), %rcx
+	movl	CPU_INFO_ILEVEL(%rcx), %edx	# oipl = cpl;
+	cmpl	%eax, %edx			# if (cpl < mtx->mtx_wantipl)
+	cmovge	%edx, %eax
+	movl	%eax, CPU_INFO_ILEVEL(%rcx)	#	cpl = mtx->mtx_wantipl;
+	/*
+	 * %edx - the old ipl
+	 * %rcx - curcpu()
+	 */
+	xorq	%rax, %rax
+#ifdef MULTIPROCESSOR
+	lock
+#endif
+	cmpxchgq	%rcx, MTX_OWNER(%rdi)	# test_and_set(mtx->mtx_owner)
+	jne	2f
+	movl	%edx, MTX_OLDIPL(%rdi)
+	movq	$1, %rax
+	ret
+
+	/* We failed to obtain the lock. splx and return 0. */
+2:	pushq	%rdi
+	movl	%edx, %edi
+	call	_C_LABEL(spllower)
+	popq	%rdi
+#ifdef DIAGNOSTIC
+	movq	CPUVAR(SELF), %rcx
+	cmpq	MTX_OWNER(%rdi), %rcx
+	je	3f
+#endif
+	xorq	%rax, %rax
+	ret
+
+#ifdef DIAGNOSTIC
+3:	movq	$4f, %rdi
+	call	_C_LABEL(panic)
+4:	.asciz	"mtx_enter: locking against myself"
+#endif
+
+
 ENTRY(mtx_leave)
 	movq	%rdi, %rax
 	xorq	%rcx, %rcx