On Tue, Feb 18, 2014 at 9:42 AM, Ludovic Courtès <l...@gnu.org> wrote: > (Dropping GDB.) > > Doug Evans <xdj...@gmail.com> skribis: > >> On Tue, Feb 18, 2014 at 3:20 AM, Ludovic Courtès <l...@gnu.org> wrote: > > [...] > >>> (I think we should aim to get rid of the signal-delivery thread >>> eventually, and I remember Mark mentioned it before too.) >> >> Note that Python queues the asyncs directly from the signal handler, >> even when it has thread support. >> I'm not sure if there are any problems in Python's implementation; >> asyncs can be queued from any thread but only the main thread runs them. >> >> Guile would need to come up with its own implementation of course; >> plus Guile can direct signals to any thread. > > There are two difficulties: > > 1. The signal handler can only call async-signal-safe functions, which > complicates things.
That's why I'm curious whether Python's solution has any problems. Someone (potentially not a Guile developer - not sure how to address copyright issues) should look into that. I will I hope, dunno how soon though. > 2. In Guile, the 'sigaction' procedure can specify the thread that > will run the async. > > Ludo'. Guile solves that by registering ahead of time which thread. I don't see it as an added difficulty. btw, I'm testing a patch that proposes augmenting Guile's signal handling support. sigaction tries to do too much. For some apps libguile needs to provide something with a finer granularity, so to speak. I see (at least) two high level problems. 1) Some apps need ability to use their own signal handlers. 2) Remove need for a separate thread. I'm not addressing (2) in this patch, though I am allowing for the day when the signal delivery thread is gone (the API needn't change). I'm addressing (1) by exporting two things: a) ability to record a signal with Guile in an async-safe way (for the present implementation that means basically by exporting the pipe-writing part of take_signal). b) ability to specify in advance which function to call and on which thread to process the signal, basically by exporting install_handler. I need to make sure these play well with sigaction. I haven't come across any problems, but it's early. :-) Thoughts?
