95 lines
2.3 KiB
C
95 lines
2.3 KiB
C
/*
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* Copyright (c) 2019 TAOS Data, Inc. <jhtao@taosdata.com>
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*
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* This program is free software: you can use, redistribute, and/or modify
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* it under the terms of the GNU Affero General Public License, version 3
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* or later ("AGPL"), as published by the Free Software Foundation.
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*
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* This program is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE.
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*
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* You should have received a copy of the GNU Affero General Public License
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* along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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#define _DEFAULT_SOURCE
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#include "tlockfree.h"
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#define TD_RWLATCH_WRITE_FLAG 0x40000000
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void taosInitRWLatch(SRWLatch *pLatch) { *pLatch = 0; }
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void taosWLockLatch(SRWLatch *pLatch) {
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SRWLatch oLatch, nLatch;
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int32_t nLoops = 0;
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// Set write flag
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while (1) {
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oLatch = atomic_load_32(pLatch);
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if (oLatch & TD_RWLATCH_WRITE_FLAG) {
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nLoops++;
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if (nLoops > 1000) {
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sched_yield();
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nLoops = 0;
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}
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continue;
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}
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nLatch = oLatch | TD_RWLATCH_WRITE_FLAG;
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if (atomic_val_compare_exchange_32(pLatch, oLatch, nLatch) == oLatch) break;
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}
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// wait for all reads end
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nLoops = 0;
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while (1) {
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oLatch = atomic_load_32(pLatch);
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if (oLatch == TD_RWLATCH_WRITE_FLAG) break;
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nLoops++;
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if (nLoops > 1000) {
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sched_yield();
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nLoops = 0;
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}
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}
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}
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// no reentrant
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int32_t taosWTryLockLatch(SRWLatch *pLatch) {
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SRWLatch oLatch, nLatch;
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oLatch = atomic_load_32(pLatch);
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if (oLatch) {
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return -1;
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}
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nLatch = oLatch | TD_RWLATCH_WRITE_FLAG;
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if (atomic_val_compare_exchange_32(pLatch, oLatch, nLatch) == oLatch) {
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return 0;
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}
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return -1;
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}
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void taosWUnLockLatch(SRWLatch *pLatch) { atomic_store_32(pLatch, 0); }
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void taosRLockLatch(SRWLatch *pLatch) {
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SRWLatch oLatch, nLatch;
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int32_t nLoops = 0;
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while (1) {
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oLatch = atomic_load_32(pLatch);
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if (oLatch & TD_RWLATCH_WRITE_FLAG) {
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nLoops++;
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if (nLoops > 1000) {
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sched_yield();
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nLoops = 0;
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}
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continue;
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}
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nLatch = oLatch + 1;
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if (atomic_val_compare_exchange_32(pLatch, oLatch, nLatch) == oLatch) break;
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}
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}
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void taosRUnLockLatch(SRWLatch *pLatch) { atomic_fetch_sub_32(pLatch, 1); }
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