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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.
// The following code runs only on g0 stack.
#include "runtime.h"
#include "arch_GOARCH.h"
#ifdef _64BIT
// 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)
#define CNT_MASK (0ull-1)
#ifdef _64BIT
#ifdef GOOS_solaris
// SPARC64 and Solaris on AMD64 uses all 64 bits of virtual addresses.
// Use low-order three bits as ABA counter.
// http://docs.oracle.com/cd/E19120-01/open.solaris/816-5138/6mba6ua5p/index.html
#undef PTR_BITS
#undef CNT_MASK
#undef PTR_MASK
#define PTR_BITS 0
#define CNT_MASK 7
#define PTR_MASK ((0ull-1)<<3)
#endif
#endif
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&CNT_MASK)<<PTR_BITS);
for(;;) {
old = runtime·atomicload64(head);
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;
for(;;) {
old = runtime·atomicload64(head);
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&CNT_MASK)<<PTR_BITS);
if(runtime·cas64(head, old, new))
return node;
}
}
void
runtime·lfstackpush_m(void)
{
runtime·lfstackpush(g->m->ptrarg[0], g->m->ptrarg[1]);
g->m->ptrarg[0] = nil;
g->m->ptrarg[1] = nil;
}
void
runtime·lfstackpop_m(void)
{
g->m->ptrarg[0] = runtime·lfstackpop(g->m->ptrarg[0]);
}
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