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

  Read of size 8 at 0x7fecf2e75fc8 by thread T2 (mutexes: write M1318):
    #0 tpool::thread_pool_generic::submit_task(tpool::task*) /tpool/tpool_generic.cc:823:9 (mariadbd+0x25fd2d2)
    #1 (anonymous namespace)::aio_uring::thread_routine((anonymous namespace)::aio_uring*) /tpool/aio_liburing.cc:173:20 (mariadbd+0x260b21b)
    #2 void std::__invoke_impl<void, void (*)((anonymous namespace)::aio_uring*), (anonymous namespace)::aio_uring*>(std::__invoke_other, void (*&&)((anonymous namespace)::aio_uring*), (anonymous namespace)::aio_uring*&&) /usr/lib/gcc/x86_64-linux-gnu/11/../../../../include/c++/11/bits/invoke.h:61:14 (mariadbd+0x260c62a)
    #3 std::__invoke_result<void (*)((anonymous namespace)::aio_uring*), (anonymous namespace)::aio_uring*>::type std::__invoke<void (*)((anonymous namespace)::aio_uring*), (anonymous namespace)::aio_uring*>(void (*&&)((anonymous namespace)::aio_uring*), (anonymous namespace)::aio_uring*&&) /usr/lib/gcc/x86_64-linux-gnu/11/../../../../include/c++/11/bits/invoke.h:96:14 (mariadbd+0x260c4ba)
    #4 void std::thread::_Invoker<std::tuple<void (*)((anonymous namespace)::aio_uring*), (anonymous namespace)::aio_uring*> >::_M_invoke<0ul, 1ul>(std::_Index_tuple<0ul, 1ul>) /usr/lib/gcc/x86_64-linux-gnu/11/../../../../include/c++/11/bits/std_thread.h:253:13 (mariadbd+0x260c442)
    #5 std::thread::_Invoker<std::tuple<void (*)((anonymous namespace)::aio_uring*), (anonymous namespace)::aio_uring*> >::operator()() /usr/lib/gcc/x86_64-linux-gnu/11/../../../../include/c++/11/bits/std_thread.h:260:11 (mariadbd+0x260c3c5)
    #6 std::thread::_State_impl<std::thread::_Invoker<std::tuple<void (*)((anonymous namespace)::aio_uring*), (anonymous namespace)::aio_uring*> > >::_M_run() /usr/lib/gcc/x86_64-linux-gnu/11/../../../../include/c++/11/bits/std_thread.h:211:13 (mariadbd+0x260c189)
    #7 <null> <null> (libstdc++.so.6+0xd230f)

  Previous write of size 8 at 0x7fecf2e75fc8 by main thread:
    #0 tpool::task::task(void (*)(void*), void*, tpool::task_group*) /tpool/task.cc:40:46 (mariadbd+0x260a138)
    #1 tpool::aiocb::aiocb() /tpool/tpool.h:147:13 (mariadbd+0x2355943)
    #2 void std::_Construct<tpool::aiocb>(tpool::aiocb*) /usr/lib/gcc/x86_64-linux-gnu/11/../../../../include/c++/11/bits/stl_construct.h:109:38 (mariadbd+0x2355845)
    #3 tpool::aiocb* std::__uninitialized_default_n_1<false>::__uninit_default_n<tpool::aiocb*, unsigned long>(tpool::aiocb*, unsigned long) /usr/lib/gcc/x86_64-linux-gnu/11/../../../../include/c++/11/bits/stl_uninitialized.h:579:3 (mariadbd+0x235576c)
    #4 tpool::aiocb* std::__uninitialized_default_n<tpool::aiocb*, unsigned long>(tpool::aiocb*, unsigned long) /usr/lib/gcc/x86_64-linux-gnu/11/../../../../include/c++/11/bits/stl_uninitialized.h:638:14 (mariadbd+0x23556e9)
    #5 tpool::aiocb* std::__uninitialized_default_n_a<tpool::aiocb*, unsigned long, tpool::aiocb>(tpool::aiocb*, unsigned long, std::allocator<tpool::aiocb>&) /usr/lib/gcc/x86_64-linux-gnu/11/../../../../include/c++/11/bits/stl_uninitialized.h:704:14 (mariadbd+0x2355641)
    #6 std::vector<tpool::aiocb, std::allocator<tpool::aiocb> >::_M_default_initialize(unsigned long) /usr/lib/gcc/x86_64-linux-gnu/11/../../../../include/c++/11/bits/stl_vector.h:1606:4 (mariadbd+0x2354f3d)
    #7 std::vector<tpool::aiocb, std::allocator<tpool::aiocb> >::vector(unsigned long, std::allocator<tpool::aiocb> const&) /usr/lib/gcc/x86_64-linux-gnu/11/../../../../include/c++/11/bits/stl_vector.h:512:9 (mariadbd+0x2354a19)
    MariaDB#8 tpool::cache<tpool::aiocb>::cache(unsigned long, tpool::cache_notification_mode) /tpool/tpool_structs.h:73:20 (mariadbd+0x2354784)
    MariaDB#9 io_slots::io_slots(int, int) /storage/innobase/os/os0file.cc:93:3 (mariadbd+0x235343b)
    MariaDB#10 os_aio_init() /storage/innobase/os/os0file.cc:3780:22 (mariadbd+0x234ebce)
    MariaDB#11 srv_start(bool) /storage/innobase/srv/srv0start.cc:1190:6 (mariadbd+0x256720c)
    MariaDB#12 innodb_init(void*) /storage/innobase/handler/ha_innodb.cc:4188:8 (mariadbd+0x1ed3bda)
    MariaDB#13 ha_initialize_handlerton(st_plugin_int*) /sql/handler.cc:659:31 (mariadbd+0xf7be06)
    MariaDB#14 plugin_initialize(st_mem_root*, st_plugin_int*, int*, char**, bool) /sql/sql_plugin.cc:1463:9 (mariadbd+0x160fa1b)
    MariaDB#15 plugin_init(int*, char**, int) /sql/sql_plugin.cc:1756:15 (mariadbd+0x160f07f)
    MariaDB#16 init_server_components() /sql/mysqld.cc:5043:7 (mariadbd+0xd70fb2)
    MariaDB#17 mysqld_main(int, char**) /sql/mysqld.cc:5655:7 (mariadbd+0xd6a9d7)
    MariaDB#18 main /sql/main.cc:34:10 (mariadbd+0xd65d18)

I think the report is incorrect: it's not possible to have such a race
condition. I've checked it by reading the code and putting assertions.
Namely, no aio I/O is possible before the end of os_aio_init().
Most probably it's some bug in TSAN. But the patch fixes around 5 related
reports and this is a step toward TSAN usefullness. Currently it reports too
much noise.

std::unique_ptr is a step toward https://isocpp.github.io/CppCoreGuidelines/CppCoreGuidelines#r11-avoid-calling-new-and-delete-explicitly
There is no std::make_unique() in C++11, however.

storage/innobase/os/os0file.cc

@@ -80,6 +80,7 @@ Created 10/21/1995 Heikki Tuuri
 
 #include <thread>
 #include <chrono>
+#include <memory>
 
 /* Per-IO operation environment*/
 class io_slots
@@ -133,8 +134,8 @@ class io_slots
 	}
 };
 
-static io_slots *read_slots;
-static io_slots *write_slots;
+static std::unique_ptr<io_slots> read_slots;
+static std::unique_ptr<io_slots> write_slots;
 
 /** Number of retries for partial I/O's */
 constexpr ulint NUM_RETRIES_ON_PARTIAL_IO = 10;
@@ -3744,6 +3745,10 @@ 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())
@@ -3774,22 +3779,21 @@ int os_aio_init()
   }
 #endif
 
-  if (!ret)
+  if (ret)
   {
-    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);
+    read_slots.reset();
+    write_slots.reset();
   }
+
   return ret;
 }
 
 
 void os_aio_free()
 {
   srv_thread_pool->disable_aio();
-  delete read_slots;
-  delete write_slots;
-  read_slots= nullptr;
-  write_slots= nullptr;
+  read_slots.reset();
+  write_slots.reset();
 }
 
 /** Wait until there are no pending asynchronous writes. */
@@ -3879,7 +3883,7 @@ 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 : write_slots;
+	io_slots* slots= type.is_read() ? read_slots.get() : write_slots.get();
 	tpool::aiocb* cb = slots->acquire();
 
 	cb->m_buffer = buf;