td-928: thread-safe 'copy on read'

also merge 'reference counting' and 'rwlatch' into 'lock-free'

src/query/inc/qExecutor.h

@@ -24,7 +24,7 @@
 #include "qtsbuf.h"
 #include "taosdef.h"
 #include "tarray.h"
-#include "tref.h"
+#include "tlockfree.h"
 #include "tsdb.h"
 #include "tsqlfunction.h"
 #include "query.h"

src/tsdb/inc/tsdbMain.h

@@ -21,11 +21,10 @@
 #include "tkvstore.h"
 #include "tlist.h"
 #include "tlog.h"
-#include "tref.h"
+#include "tlockfree.h"
 #include "tsdb.h"
 #include "tskiplist.h"
 #include "tutil.h"
-#include "trwlatch.h"
 
 #ifdef __cplusplus
 extern "C" {

src/util/inc/tcache.h

@@ -21,7 +21,7 @@ extern "C" {
 #endif
 
 #include "os.h"
-#include "tref.h"
+#include "tlockfree.h"
 #include "hash.h"
 
 typedef void (*__cache_free_fn_t)(void*);

src/util/inc/tref.h → src/util/inc/tlockfree.h

@@ -12,12 +12,17 @@
  * You should have received a copy of the GNU Affero General Public License
  * along with this program. If not, see <http://www.gnu.org/licenses/>.
  */
-
-#ifndef TDENGINE_TREF_H
-#define TDENGINE_TREF_H
+#ifndef __TD_LOCK_FREE_H__
+#define __TD_LOCK_FREE_H__
 
 #include "os.h"
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+
+// reference counting
 typedef void (*_ref_fn_t)(const void* pObj);
 
 #define T_REF_DECLARE() \
@@ -55,4 +60,47 @@ typedef void (*_ref_fn_t)(const void* pObj);
 
 #define T_REF_VAL_GET(x) (x)->_ref.val
 
-#endif  // TDENGINE_TREF_H
+
+
+// single writer multiple reader lock
+typedef int32_t SRWLatch;
+
+void taosInitRWLatch(SRWLatch *pLatch);
+void taosWLockLatch(SRWLatch *pLatch);
+void taosWUnLockLatch(SRWLatch *pLatch);
+void taosRLockLatch(SRWLatch *pLatch);
+void taosRUnLockLatch(SRWLatch *pLatch);
+
+
+
+// copy on read
+#define taosCorBeginRead(x) for (uint32_t i_ = 1; 1; ++i_) { \
+    int32_t old_ = atomic_load_32(x); \
+    if (old_ & 0x00000001) { \
+      if (i_ % 1000 == 0) { \
+        sched_yield(); \
+      } \
+      continue; \
+    }
+
+#define taosCorEndRead(x) \
+    if (atomic_load_32(x) == old_) { \
+      break; \
+    } \
+  }
+
+#define taosCorBeginWrite(x) taosCorBeginRead(x) \
+    if (atomic_val_compare_exchange_32((x), old_, old_ + 1) != old_) { \
+        continue; \
+    }
+
+#define taosCorEndWrite(x) atomic_add_fetch_32((x), 1); \
+    break; \
+  }
+
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif

src/util/inc/trwlatch.h

-/*
- * Copyright (c) 2019 TAOS Data, Inc. <jhtao@taosdata.com>
- *
- * This program is free software: you can use, redistribute, and/or modify
- * it under the terms of the GNU Affero General Public License, version 3
- * or later ("AGPL"), as published by the Free Software Foundation.
- *
- * This program is distributed in the hope that it will be useful, but WITHOUT
- * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
- * FITNESS FOR A PARTICULAR PURPOSE.
- *
- * You should have received a copy of the GNU Affero General Public License
- * along with this program. If not, see <http://www.gnu.org/licenses/>.
- */
-#ifndef __TD_RWLATCH_H__
-#define __TD_RWLATCH_H__
-
-#ifdef __cplusplus
-extern "C" {
-#endif
-
-#include <stdint.h>
-
-typedef int32_t SRWLatch;
-
-void taosInitRWLatch(SRWLatch *pLatch);
-void taosWLockLatch(SRWLatch *pLatch);
-void taosWUnLockLatch(SRWLatch *pLatch);
-void taosRLockLatch(SRWLatch *pLatch);
-void taosRUnLockLatch(SRWLatch *pLatch);
-
-#ifdef __cplusplus
-}
-#endif
-
-#endif

src/util/src/trwlatch.c → src/util/src/tlockfree.c

@@ -15,8 +15,7 @@
 // #define _GNU_SOURCE
 // #include <pthread.h>
 
-#include "trwlatch.h"
-#include "os.h"
+#include "tlockfree.h"
 
 #define TD_RWLATCH_WRITE_FLAG 0x40000000