[Async-sig] "read-write" synchronization

[Chris Jerdonek]

On Sun, Jun 25, 2017 at 3:09 PM, Nathaniel Smith <njs at pobox.com> wrote:
> On Sun, Jun 25, 2017 at 2:13 PM, Chris Jerdonek
> <chris.jerdonek at gmail.com> wrote:
>> I'm using asyncio, and the synchronization primitives that asyncio
>> exposes are relatively simple [1]. Have options for async read-write
>> synchronization already been discussed in any detail?
>
> As a general comment: I used to think rwlocks were a simple extension
> to regular locks, but it turns out there's actually this huge increase
> in design complexity. Do you want your lock to be read-biased,
> write-biased, task-fair, phase-fair? Can you acquire a write lock if
> you already hold one (i.e., are write locks reentrant)? What about
> acquiring a read lock if you already hold the write lock? Can you
> atomically upgrade/downgrade a lock? This makes it much harder to come
> up with a one-size-fits-all design suitable for adding to something
> like the python stdlib.

I agree. And my point about asyncio's primitives wasn't a criticism or
request that more be added. I was asking more if there has been any
discussion of general approaches and patterns that take advantage of
the event loop's single thread, etc.

Maybe what I'll do is briefly write up the approach I have in mind,
and people can let me know if I'm on the right track. :)

--Chris