PROPOSAL(S): threadWaitError and threadWaitErrorSTM

[Andreas Voellmy]

epoll automatically always waits on EPOLLERR, and it looks like this will
just lead to threadWait functions to return from the call.

Can you write a small test case to check if the current behavior works (or
not) with existing threadWait functions?

Andi


On Tue, Mar 18, 2014 at 6:46 AM, Merijn Verstraaten
<merijn at inconsistent.nl>wrote:

> Seems rather simple, just use epoll's EPOLLERR event type. There's more
> types (like the EPOLLPRI type you mentioned), but I would not argue for
> adding those as such events may not be portable to platforms that don't
> support epoll (i.e. platforms that only have kqueue/select), whereas
> EPOLLERR should be available in some form for all platforms.
>
> Cheers,
> Merijn
>
>
> On Mar 17, 2014, at 14:23 , Andreas Voellmy wrote:
>
> Hi Merijn,
>
> I see how you'd wait for exceptional conditions using select(). Epoll is a
> bit different... How would you do it with epoll? Is it using the EPOLLPRI
> event type?
>
> Andi
>
>
> On Sun, Mar 16, 2014 at 1:16 PM, Merijn Verstraaten <
> merijn at inconsistent.nl> wrote:
>
>> I just went with the common documentation name, I know this includes
>> out-of-band data, etc. If it makes you happier, feel free to consider this
>> proposal with s/Error/Exceptional, regardless of how it's called, it'd be
>> nice if we could use this from within Haskell.
>>
>> Cheers,
>> Merijn
>>
>>
>> On Mar 16, 2014, at 16:09 , Brandon Allbery wrote:
>>
>> On Sun, Mar 16, 2014 at 10:25 AM, Merijn Verstraaten <
>> merijn at inconsistent.nl> wrote:
>>
>>> threadWaitError :: Fd -> IO ()
>>> threadWaitErrorSTM :: Fd -> IO (STM (), IO ())
>>>
>>> to allow for blocking on detecting error condition on file descriptors,
>>> similar to what C's select() allows.
>>>
>>
>> If you mean the third bitmask, it is not for errors (notwithstanding the
>> documentation on some systems); an "exceptional condition" is not an error,
>> it's MSG_OOB data. Errors show as "ready" on the appropriate mask (read or
>> write) since a read (resp. write) will return immediately with the error
>> instead of blocking.
>>
>> See
>> http://stackoverflow.com/questions/1342712/nix-select-and-exceptfds-errorfds-semanticsand
>> http://man7.org/linux/man-pages/man2/select_tut.2.html for more
>> information.
>>
>> --
>> brandon s allbery kf8nh                               sine nomine
>> associates
>> allbery.b at gmail.com
>> ballbery at sinenomine.net
>> unix, openafs, kerberos, infrastructure, xmonad
>> http://sinenomine.net
>>
>>
>>
>> _______________________________________________
>> Libraries mailing list
>> Libraries at haskell.org
>> http://www.haskell.org/mailman/listinfo/libraries
>>
>>
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://www.haskell.org/pipermail/libraries/attachments/20140321/069d74b4/attachment.html>