67 lines
1.4 KiB
C
67 lines
1.4 KiB
C
// 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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#include "runtime.h"
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#include "arch.h"
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#if __SIZEOF_POINTER__ == 8
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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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#else
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# define PTR_BITS 32
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#endif
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#define PTR_MASK ((1ull<<PTR_BITS)-1)
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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((uintptr)node != ((uintptr)node&PTR_MASK)) {
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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 = (uint64)(uintptr)node|(((uint64)node->pushcnt)<<PTR_BITS);
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old = runtime_atomicload64(head);
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for(;;) {
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node->next = (LFNode*)(uintptr)(old&PTR_MASK);
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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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old = runtime_atomicload64(head);
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for(;;) {
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if(old == 0)
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return nil;
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node = (LFNode*)(uintptr)(old&PTR_MASK);
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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 = (uint64)(uintptr)node2|(((uint64)node2->pushcnt)<<PTR_BITS);
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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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LFNode* runtime_lfstackpop2(uint64*)
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asm("runtime.lfstackpop2");
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LFNode*
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runtime_lfstackpop2(uint64 *head)
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{
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return runtime_lfstackpop(head);
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}
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