96 lines
2.4 KiB
Plaintext
96 lines
2.4 KiB
Plaintext
// Copyright 2012 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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// Lock-free stack.
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package runtime
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#include "runtime.h"
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#include "arch.h"
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#if __SIZEOF_POINTER__ == 8
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// SPARC64 and Solaris on AMD64 uses all 64 bits of virtual addresses.
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// Use low-order three bits as ABA counter.
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// http://docs.oracle.com/cd/E19120-01/open.solaris/816-5138/6mba6ua5p/index.html
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# if defined(__sparc__) || (defined(__sun__) && defined(__amd64__))
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static inline uint64 lfPack(LFNode *node, uintptr cnt) {
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return ((uint64)(node)) | ((cnt)&7);
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}
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static inline LFNode* lfUnpack(uint64 val) {
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return (LFNode*)(val&~7);
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}
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# else
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# if defined(__aarch64__)
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// Depending on the kernel options, pointers on arm64 can have up to 48 significant
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// bits (see https://www.kernel.org/doc/Documentation/arm64/memory.txt).
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# define PTR_BITS 48
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# else
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// Amd64 uses 48-bit virtual addresses, 47-th bit is used as kernel/user flag.
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// So we use 17msb of pointers as ABA counter.
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# define PTR_BITS 47
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# endif
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# define CNT_BITS (64 - PTR_BITS + 3)
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static inline uint64 lfPack(LFNode *node, uintptr cnt) {
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return ((uint64)(node)<<(64-PTR_BITS)) | (cnt&(((1<<CNT_BITS)-1)));
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}
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static inline LFNode* lfUnpack(uint64 val) {
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return (LFNode*)((val >> CNT_BITS) << 3);
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}
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# endif
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#else
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static inline uint64 lfPack(LFNode *node, uintptr cnt) {
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return ((uint64)(uintptr)(node)<<32) | cnt;
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}
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static inline LFNode* lfUnpack(uint64 val) {
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return (LFNode*)(uintptr)(val >> 32);
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}
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#endif
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void
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runtime_lfstackpush(uint64 *head, LFNode *node)
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{
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uint64 old, new;
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if(node != lfUnpack(lfPack(node, 0))) {
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runtime_printf("p=%p\n", node);
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runtime_throw("runtime_lfstackpush: invalid pointer");
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}
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node->pushcnt++;
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new = lfPack(node, node->pushcnt);
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for(;;) {
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old = runtime_atomicload64(head);
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node->next = lfUnpack(old);
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if(runtime_cas64(head, old, new))
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break;
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}
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}
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LFNode*
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runtime_lfstackpop(uint64 *head)
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{
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LFNode *node, *node2;
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uint64 old, new;
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for(;;) {
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old = runtime_atomicload64(head);
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if(old == 0)
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return nil;
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node = lfUnpack(old);
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node2 = runtime_atomicloadp(&node->next);
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new = 0;
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if(node2 != nil)
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new = lfPack(node2, node2->pushcnt);
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if(runtime_cas64(head, old, new))
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return node;
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}
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}
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func lfstackpush_go(head *uint64, node *LFNode) {
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runtime_lfstackpush(head, node);
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}
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func lfstackpop_go(head *uint64) (node *LFNode) {
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node = runtime_lfstackpop(head);
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}
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