MDEV-7108 changed the type of the variable srv_fatal_semaphore_wait_threshold from ulint to ulong but failed to adjust the assignments accordingly.
In MariaDB 10.2, some wrong code reads like this:

			my_atomic_addlint(

				&srv_fatal_semaphore_wait_threshold,

				SRV_SEMAPHORE_WAIT_EXTENSION);

In MariaDB 10.1, it reads like this:

			os_increment_counter_by_amount(

				server_mutex,

                                srv_fatal_semaphore_wait_threshold,

				SRV_SEMAPHORE_WAIT_EXTENSION);

Both of these forms expect the data type to be ulint.

As far as I understand, on most platforms sizeof(ulong)==sizeof(ulint) would hold. Most notably, the sizes are different on 64-bit WIndows (4 and 8 bytes).

The problem was found by wlad by compiling 10.3 cmake -DWITH_ASAN and running tests on Windows.