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

Trivial fil_space_t::n_pending_ops transition. Since it is not
obvious which memory barriers are supposed to be issued, seq_cst
memory order was preserved.

Author: svoj

storage/innobase/fil/fil0fil.cc

@@ -2297,7 +2297,7 @@ fil_check_pending_ops(const fil_space_t* space, ulint count)
 		return 0;
 	}
 
-	if (ulint n_pending_ops = my_atomic_loadlint(&space->n_pending_ops)) {
+	if (ulint n_pending_ops = space->n_pending_ops) {
 
 		if (count > 5000) {
 			ib::warn() << "Trying to close/delete/truncate"

storage/innobase/include/fil0fil.h

@@ -133,8 +133,8 @@ struct fil_space_t {
 	dropped. An example is change buffer merge.
 	The tablespace cannot be dropped while this is nonzero,
 	or while fil_node_t::n_pending is nonzero.
-	Protected by fil_system.mutex and my_atomic_loadlint() and friends. */
-	ulint		n_pending_ops;
+	Protected by fil_system.mutex and std::atomic. */
+	std::atomic<ulint>		n_pending_ops;
 	/** Number of pending block read or write operations
 	(when a write is imminent or a read has recently completed).
 	The tablespace object cannot be freed while this is nonzero,
@@ -244,20 +244,11 @@ struct fil_space_t {
 	void close();
 
 	/** Acquire a tablespace reference. */
-	void acquire() { my_atomic_addlint(&n_pending_ops, 1); }
+	void acquire() { n_pending_ops++; }
 	/** Release a tablespace reference. */
-	void release()
-	{
-		ut_ad(referenced());
-		my_atomic_addlint(&n_pending_ops, ulint(-1));
-	}
+	void release() { ut_ad(referenced()); n_pending_ops--; }
 	/** @return whether references are being held */
-	bool referenced() { return my_atomic_loadlint(&n_pending_ops); }
-	/** @return whether references are being held */
-	bool referenced() const
-	{
-		return const_cast<fil_space_t*>(this)->referenced();
-	}
+	bool referenced() const { return n_pending_ops; }
 
 	/** Acquire a tablespace reference for I/O. */
 	void acquire_for_io() { n_pending_ios++; }

storage/innobase/include/sync0types.h

@@ -1117,15 +1117,6 @@ enum rw_lock_flag_t {
 
 #endif /* UNIV_INNOCHECKSUM */
 
-static inline ulint my_atomic_addlint(ulint *A, ulint B)
-{
-#ifdef _WIN64
-  return ulint(my_atomic_add64((volatile int64*)A, B));
-#else
-  return ulint(my_atomic_addlong(A, B));
-#endif
-}
-
 static inline ulint my_atomic_loadlint(const ulint *A)
 {
 #ifdef _WIN64
@@ -1135,15 +1126,6 @@ static inline ulint my_atomic_loadlint(const ulint *A)
 #endif
 }
 
-static inline lint my_atomic_addlint(volatile lint *A, lint B)
-{
-#ifdef _WIN64
-  return my_atomic_add64((volatile int64*)A, B);
-#else
-  return my_atomic_addlong(A, B);
-#endif
-}
-
 static inline lint my_atomic_loadlint(const lint *A)
 {
 #ifdef _WIN64