Re: System asyncs and mutexes: a combination prone to deadlocks

[Ludovic Courtès]

Mark H Weaver <address@hidden> skribis:

> I wrote:
>> System asyncs can run while mutexes are locked.  Asyncs can run
>> arbitrary scheme code, so of course mutexes will often be locked within
>> asyncs as well.  So what happens if an async tries to lock a mutex that
>> has already been locked by the same thread?  Deadlock, of course.
>
> I've mulled this over, and I think the solution will involve finding all
> of the mutexes that are likely to be locked within asyncs without the
> user's knowledge (i.e. essentially all mutexes used in core Guile, both
> in C and in Scheme), and ensuring that asyncs are disabled before any of
> those mutexes are locked.
>
> What do you think?

(At the risk of looking silly:)

Alternately, what about documenting system asyncs as having restrictions
on the type of code they can run?

For example, can you think of a way to achieve what you wanted in (ice-9
popen) without resorting to system asyncs?

My 2¢,
Ludo’.