src/runtime/lfstack.go

   1 // Copyright 2012 The Go Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style
   3 // license that can be found in the LICENSE file.
   4
   5 // Lock-free stack.
   6 // The following code runs only on g0 stack.
   7
   8 package runtime
   9
  10 import "unsafe"
  11
  12 func lfstackpush(head *uint64, node *lfnode) {
  13         node.pushcnt++
  14         new := lfstackPack(node, node.pushcnt)
  15         if node1, _ := lfstackUnpack(new); node1 != node {
  16                 println("runtime: lfstackpush invalid packing: node=", node, " cnt=", hex(node.pushcnt), " packed=", hex(new), " -> node=", node1, "\n")
  17                 gothrow("lfstackpush")
  18         }
  19         for {
  20                 old := atomicload64(head)
  21                 node.next, _ = lfstackUnpack(old)
  22                 if cas64(head, old, new) {
  23                         break
  24                 }
  25         }
  26 }
  27
  28 func lfstackpop(head *uint64) unsafe.Pointer {
  29         for {
  30                 old := atomicload64(head)
  31                 if old == 0 {
  32                         return nil
  33                 }
  34                 node, _ := lfstackUnpack(old)
  35                 node2 := (*lfnode)(atomicloadp(unsafe.Pointer(&node.next)))
  36                 new := uint64(0)
  37                 if node2 != nil {
  38                         new = lfstackPack(node2, node2.pushcnt)
  39                 }
  40                 if cas64(head, old, new) {
  41                         return unsafe.Pointer(node)
  42                 }
  43         }
  44 }