MDEV-17441 - InnoDB transition to C++11 atomics

Almost trivial ReadView::m_state transition. Since C++11 doesn't seem to
allow mixed (atomic and non-atomic) access to atomic variables, we have
to perform all accesses atomically.

storage/innobase/include/buf0buf.h

@@ -41,7 +41,6 @@ Created 11/5/1995 Heikki Tuuri
 #include "os0proc.h"
 #include "log0log.h"
 #include "srv0srv.h"
-#include "my_atomic.h"
 #include <ostream>
 
 // Forward declaration

storage/innobase/include/read0types.h

@@ -66,7 +66,14 @@ class ReadView
     Close view:
     READ_VIEW_STATE_OPEN -> READ_VIEW_STATE_CLOSED
   */
-  int32_t m_state;
+  std::atomic<uint32_t> m_state;
+
+
+  /** m_state getter for ReadView owner thread */
+  uint32_t state() const
+  {
+    return m_state.load(std::memory_order_relaxed);
+  }
 
 
 public:
@@ -134,35 +141,36 @@ class ReadView
     Closes the view.
 
     View becomes not visible to purge thread.
+
+    This method is intended to be called by ReadView owner thread, thus
+    m_state cannot change.
   */
   void close()
   {
-    ut_ad(m_state == READ_VIEW_STATE_CLOSED ||
-          m_state == READ_VIEW_STATE_OPEN);
-    if (m_state == READ_VIEW_STATE_OPEN)
-      my_atomic_store32_explicit(&m_state, READ_VIEW_STATE_CLOSED,
-                                 MY_MEMORY_ORDER_RELAXED);
+    ut_ad(state() == READ_VIEW_STATE_CLOSED ||
+          state() == READ_VIEW_STATE_OPEN);
+    m_state.store(READ_VIEW_STATE_CLOSED, std::memory_order_relaxed);
   }
 
 
   /** m_state getter for trx_sys::clone_oldest_view() trx_sys::size(). */
-  int32_t get_state() const
+  uint32_t get_state() const
   {
-    return my_atomic_load32_explicit(const_cast<int32*>(&m_state),
-                                     MY_MEMORY_ORDER_ACQUIRE);
+    return m_state.load(std::memory_order_acquire);
   }
 
 
   /**
     Returns true if view is open.
 
-    Only used by view owner thread, thus we can omit atomic operations.
+    This method is intended to be called by ReadView owner thread, thus
+    m_state cannot change.
   */
   bool is_open() const
   {
-    ut_ad(m_state == READ_VIEW_STATE_OPEN ||
-          m_state == READ_VIEW_STATE_CLOSED);
-    return m_state == READ_VIEW_STATE_OPEN;
+    ut_ad(state() == READ_VIEW_STATE_OPEN ||
+          state() == READ_VIEW_STATE_CLOSED);
+    return state() == READ_VIEW_STATE_OPEN;
   }
 
 

storage/innobase/include/ut0ut.h

@@ -45,7 +45,6 @@ Created 1/20/1994 Heikki Tuuri
 #include <stdarg.h>
 
 #include <string>
-#include <my_atomic.h>
 
 /** Index name prefix in fast index creation, as a string constant */
 #define TEMP_INDEX_PREFIX_STR	"\377"

storage/innobase/read/read0read.cc

@@ -200,7 +200,7 @@ inline void ReadView::snapshot(trx_t *trx)
 void ReadView::open(trx_t *trx)
 {
   ut_ad(this == &trx->read_view);
-  switch (m_state)
+  switch (state())
   {
   case READ_VIEW_STATE_OPEN:
     ut_ad(!srv_read_only_mode);
@@ -254,8 +254,7 @@ void ReadView::open(trx_t *trx)
     */
     mutex_enter(&trx_sys.mutex);
     mutex_exit(&trx_sys.mutex);
-    my_atomic_store32_explicit(&m_state, READ_VIEW_STATE_SNAPSHOT,
-                               MY_MEMORY_ORDER_RELAXED);
+    m_state.store(READ_VIEW_STATE_SNAPSHOT, std::memory_order_relaxed);
     break;
   default:
     ut_ad(0);
@@ -264,8 +263,7 @@ void ReadView::open(trx_t *trx)
   snapshot(trx);
 reopen:
   m_creator_trx_id= trx->id;
-  my_atomic_store32_explicit(&m_state, READ_VIEW_STATE_OPEN,
-                             MY_MEMORY_ORDER_RELEASE);
+  m_state.store(READ_VIEW_STATE_OPEN, std::memory_order_release);
 }
 
 
@@ -284,7 +282,7 @@ void trx_sys_t::clone_oldest_view()
   for (const trx_t *trx= UT_LIST_GET_FIRST(trx_list); trx;
        trx= UT_LIST_GET_NEXT(trx_list, trx))
   {
-    int32_t state;
+    uint32_t state;
 
     while ((state= trx->read_view.get_state()) == READ_VIEW_STATE_SNAPSHOT)
       ut_delay(1);