g_slice_alloc hangs on child process on fork

When a fork is called other threads are doing memory allocations, g_slice might have a mutex locked at that point. So any new allocation in the child process of the fork, then will hang in g_slice_alloc.

G_SLICE=always-malloc does not suffer of the issue.

Here is an example of program that would hang.

If it does not reproduces, try increasing THREAD_N and/or ALLOC_N.