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// 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.
#include "runtime.h"
#include "arch.h"
#if __SIZEOF_POINTER__ == 8
// Amd64 uses 48-bit virtual addresses, 47-th bit is used as kernel/user flag.
// So we use 17msb of pointers as ABA counter.
# define PTR_BITS 47
#else
# define PTR_BITS 32
#endif
#define PTR_MASK ((1ull<<PTR_BITS)-1)
void
runtime_lfstackpush(uint64 *head, LFNode *node)
{
uint64 old, new;
if((uintptr)node != ((uintptr)node&PTR_MASK)) {
runtime_printf("p=%p\n", node);
runtime_throw("runtime_lfstackpush: invalid pointer");
}
node->pushcnt++;
new = (uint64)(uintptr)node|(((uint64)node->pushcnt)<<PTR_BITS);
old = runtime_atomicload64(head);
for(;;) {
node->next = (LFNode*)(uintptr)(old&PTR_MASK);
if(runtime_cas64(head, &old, new))
break;
}
}
LFNode*
runtime_lfstackpop(uint64 *head)
{
LFNode *node, *node2;
uint64 old, new;
old = runtime_atomicload64(head);
for(;;) {
if(old == 0)
return nil;
node = (LFNode*)(uintptr)(old&PTR_MASK);
node2 = runtime_atomicloadp(&node->next);
new = 0;
if(node2 != nil)
new = (uint64)(uintptr)node2|(((uint64)node2->pushcnt)<<PTR_BITS);
if(runtime_cas64(head, &old, new))
return node;
}
}
LFNode* runtime_lfstackpop2(uint64*)
asm("runtime.lfstackpop2");
LFNode*
runtime_lfstackpop2(uint64 *head)
{
return runtime_lfstackpop(head);
}
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