Crashes in dlmalloc that occur in a worker can lock up the entire application

We have had reports of an issue where a crash in dlmalloc (possible due to memory corruption) that happen on a worker can cause the entire application to freeze and the error doesn't get correctly reported. We think this is because the thread crashes while holding some global malloc lock which means the main thread is likely to end of blocked on malloc/free.

Ideally a crash like this would bring own all threads asynchronously but we can't do that with workers.