MDEV-28935 crash in io_slots::release

Revert "TSAN: data race on vptr (ctor/dtor vs virtual call)"

This reverts commit 78084fa.

This commit was done to please TSAN, which falsely reported an error
where there was none.
Yet as consequence, it could cause a real error, a crash in os_aio_free on
shutdown

storage/innobase/os/os0file.cc

@@ -79,7 +79,6 @@ Created 10/21/1995 Heikki Tuuri
 
 #include <thread>
 #include <chrono>
-#include <memory>
 
 /* Per-IO operation environment*/
 class io_slots
@@ -133,8 +132,8 @@ class io_slots
 	}
 };
 
-static std::unique_ptr<io_slots> read_slots;
-static std::unique_ptr<io_slots> write_slots;
+static io_slots *read_slots;
+static io_slots *write_slots;
 
 /** Number of retries for partial I/O's */
 constexpr ulint NUM_RETRIES_ON_PARTIAL_IO = 10;
@@ -3675,10 +3674,6 @@ int os_aio_init()
   int max_read_events= int(srv_n_read_io_threads *
                            OS_AIO_N_PENDING_IOS_PER_THREAD);
   int max_events= max_read_events + max_write_events;
-
-  read_slots.reset(new io_slots(max_read_events, srv_n_read_io_threads));
-  write_slots.reset(new io_slots(max_write_events, srv_n_write_io_threads));
-
   int ret;
 #if LINUX_NATIVE_AIO
   if (srv_use_native_aio && !is_linux_native_aio_supported())
@@ -3709,21 +3704,22 @@ int os_aio_init()
   }
 #endif
 
-  if (ret)
+  if (!ret)
   {
-    read_slots.reset();
-    write_slots.reset();
+    read_slots= new io_slots(max_read_events, srv_n_read_io_threads);
+    write_slots= new io_slots(max_write_events, srv_n_write_io_threads);
   }
-
   return ret;
 }
 
 
 void os_aio_free()
 {
   srv_thread_pool->disable_aio();
-  read_slots.reset();
-  write_slots.reset();
+  delete read_slots;
+  delete write_slots;
+  read_slots= nullptr;
+  write_slots= nullptr;
 }
 
 /** Wait until there are no pending asynchronous writes. */
@@ -3812,7 +3808,7 @@ dberr_t os_aio(const IORequest &type, void *buf, os_offset_t offset, size_t n)
 	}
 
 	compile_time_assert(sizeof(IORequest) <= tpool::MAX_AIO_USERDATA_LEN);
-	io_slots* slots= type.is_read() ? read_slots.get() : write_slots.get();
+	io_slots* slots= type.is_read() ? read_slots : write_slots;
 	tpool::aiocb* cb = slots->acquire();
 
 	cb->m_buffer = buf;