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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.
package runtime
#include "runtime.h"
#include "arch.h"
#if __SIZEOF_POINTER__ == 8
// 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
# if defined(__sparc__) || (defined(__sun__) && defined(__amd64__))
static inline uint64 lfPack(LFNode *node, uintptr cnt) {
return ((uint64)(node)) | ((cnt)&7);
}
static inline LFNode* lfUnpack(uint64 val) {
return (LFNode*)(val&~7);
}
# else
# if defined(__aarch64__)
// Depending on the kernel options, pointers on arm64 can have up to 48 significant
// bits (see https://www.kernel.org/doc/Documentation/arm64/memory.txt).
# define PTR_BITS 48
# else
// 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
# endif
# define CNT_BITS (64 - PTR_BITS + 3)
static inline uint64 lfPack(LFNode *node, uintptr cnt) {
return ((uint64)(node)<<(64-PTR_BITS)) | (cnt&(((1<<CNT_BITS)-1)));
}
static inline LFNode* lfUnpack(uint64 val) {
return (LFNode*)((val >> CNT_BITS) << 3);
}
# endif
#else
static inline uint64 lfPack(LFNode *node, uintptr cnt) {
return ((uint64)(uintptr)(node)<<32) | cnt;
}
static inline LFNode* lfUnpack(uint64 val) {
return (LFNode*)(uintptr)(val >> 32);
}
#endif
void
runtime_lfstackpush(uint64 *head, LFNode *node)
{
uint64 old, new;
if(node != lfUnpack(lfPack(node, 0))) {
runtime_printf("p=%p\n", node);
runtime_throw("runtime_lfstackpush: invalid pointer");
}
node->pushcnt++;
new = lfPack(node, node->pushcnt);
for(;;) {
old = runtime_atomicload64(head);
node->next = lfUnpack(old);
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 = lfUnpack(old);
node2 = runtime_atomicloadp(&node->next);
new = 0;
if(node2 != nil)
new = lfPack(node2, node2->pushcnt);
if(runtime_cas64(head, old, new))
return node;
}
}
func lfstackpush_go(head *uint64, node *LFNode) {
runtime_lfstackpush(head, node);
}
func lfstackpop_go(head *uint64) (node *LFNode) {
node = runtime_lfstackpop(head);
}
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