MySQL Bug #72809 - InnoDB Linux native aio setup missing barrier after setup

memory barrier at end of setting up innodb aio

we need a memory barrier here as otherwise when IO threads start they

can get a stale view of the data structure.

It turns out that POWER8 is fast enough with large enough caches that

this can actually be a problem.

You can reproduce this by attempting to do a lot of writes shortly after

server startup - you'll hit a really odd assert.

Index: mysql-5.6.17/storage/innobase/os/os0file.cc

===================================================================

--- mysql-5.6.17.orig/storage/innobase/os/os0file.cc

+++ mysql-5.6.17/storage/innobase/os/os0file.cc

@@ -3782,7 +3782,7 @@ skip_native_aio:

                slot->ret = 0;

 #endif /* WIN_ASYNC_IO */

        }

-

+       __sync_synchronize();

        return(array);

 }