[dev.cc] runtime: convert parallel support code from C to Go
The conversion was done with an automated tool and then
modified only as necessary to make it compile and run.
[This CL is part of the removal of C code from package runtime.
See golang.org/s/dev.cc for an overview.]
LGTM=r
R=r, austin
CC=dvyukov, golang-codereviews, iant, khr
https://golang.org/cl/172250043
diff --git a/src/runtime/lfstack.go b/src/runtime/lfstack.go
new file mode 100644
index 0000000..c5dc94f
--- /dev/null
+++ b/src/runtime/lfstack.go
@@ -0,0 +1,51 @@
+// Copyright 2012 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Lock-free stack.
+// The following code runs only on g0 stack.
+
+package runtime
+
+import "unsafe"
+
+const (
+ // lfPtrBits and lfCountMask are defined in lfstack_*.go.
+ lfPtrMask = 1<<lfPtrBits - 1
+)
+
+func lfstackpush(head *uint64, node *lfnode) {
+ unode := uintptr(unsafe.Pointer(node))
+ if unode&^lfPtrMask != 0 {
+ print("p=", node, "\n")
+ gothrow("lfstackpush: invalid pointer")
+ }
+
+ node.pushcnt++
+ new := uint64(unode) | (uint64(node.pushcnt)&lfCountMask)<<lfPtrBits
+ for {
+ old := atomicload64(head)
+ node.next = (*lfnode)(unsafe.Pointer(uintptr(old & lfPtrMask)))
+ if cas64(head, old, new) {
+ break
+ }
+ }
+}
+
+func lfstackpop(head *uint64) unsafe.Pointer {
+ for {
+ old := atomicload64(head)
+ if old == 0 {
+ return nil
+ }
+ node := (*lfnode)(unsafe.Pointer(uintptr(old & lfPtrMask)))
+ node2 := (*lfnode)(atomicloadp(unsafe.Pointer(&node.next)))
+ new := uint64(0)
+ if node2 != nil {
+ new = uint64(uintptr(unsafe.Pointer(node2))) | uint64(node2.pushcnt&lfCountMask)<<lfPtrBits
+ }
+ if cas64(head, old, new) {
+ return unsafe.Pointer(node)
+ }
+ }
+}
