From: Eli Zaretskii <eliz@gnu.org>
To: Akira Kyle <ak@akirakyle.com>
Cc: p.stephani2@gmail.com, emacs-devel@gnu.org, yyoncho@gmail.com,
monnier@iro.umontreal.ca, all_but_last@163.com
Subject: Re: "Asynchronous Requests from Emacs Dynamic Modules"
Date: Sat, 31 Oct 2020 22:18:53 +0200 [thread overview]
Message-ID: <831rhegnde.fsf@gnu.org> (raw)
In-Reply-To: <86ft5ufb95.fsf@akirakyle.com> (message from Akira Kyle on Sat, 31 Oct 2020 13:25:58 -0600)
> From: Akira Kyle <ak@akirakyle.com>
> Cc: yyoncho <yyoncho@gmail.com>, all_but_last@163.com, emacs-devel@gnu.org,
> Stefan Monnier <monnier@iro.umontreal.ca>, Philipp Stephani
> <p.stephani2@gmail.com>
> Date: Sat, 31 Oct 2020 13:25:58 -0600
>
> 1) Chris Wellon's solution in the article I linked using the
> SIGUSR1 signal which Emacs handles in the event queue notify the
> running Lisp Thread that it should call back into module
> functions. This idea could be expanded to allow modules to define
> their own events and lisp handlers that will respond to them.
A terrible design, if you ask me. Reminds me how timers worked in
Emacs long ago: we had an external program which would periodically
deliver a signal to Emacs. We switched off of that to what we have
now, for good reasons.
And please keep in mind that doing anything non-trivial from a signal
handler is inherently unsafe.
> 2) Stefan's and Philipp's proposal of using the process interface
> with file descriptors to pipes and perhaps `process-filter` to
> notify the Lisp Thread that it should call back into the module
> functions.
This is the way to go, IMO. This is how Emacs itself handles async
events, so the infrastructure for doing this, both in C and in Lisp,
already exists, and is mature. All you need is use it.
> 3) yyoncho's proposal to use the lisp threading interface,
> specifically condition variables to allow dynamic modules to
> `condition-notify`.
This is unworkable within the current design of Lisp threads.
condition-notify releases the global lock, something that under the
current design cannot be done at an arbitrary time, because it could
cause two threads run in parallel.
> I think the most natural solution would be a dynamic module
> interface that allows grabbing and releasing Lisp's global thread
> lock.
I encourage you to study how threading works in Emacs (the code is in
thread.c). I'm sure you will see right away why this cannot be done
without a complete redesign of how switching threads works. There's
no way of interrupting a running Lisp thread in an arbitrary place and
switching to another thread.
next prev parent reply other threads:[~2020-10-31 20:18 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-30 21:35 "Asynchronous Requests from Emacs Dynamic Modules" Akira Kyle
2020-10-30 22:39 ` Stefan Monnier
2020-10-31 3:18 ` Zhu Zihao
2020-10-31 7:45 ` Eli Zaretskii
2020-10-31 8:02 ` yyoncho
2020-10-31 9:13 ` Eli Zaretskii
2020-10-31 9:45 ` yyoncho
2020-10-31 10:43 ` Eli Zaretskii
2020-10-31 19:25 ` Akira Kyle
2020-10-31 20:18 ` Eli Zaretskii [this message]
2020-11-01 0:14 ` Akira Kyle
2020-11-01 18:28 ` Eli Zaretskii
2020-11-01 20:15 ` Akira Kyle
2020-11-01 20:51 ` async-await (was: Re: "Asynchronous Requests from Emacs Dynamic Modules") Philipp Stephani
2020-11-02 15:22 ` "Asynchronous Requests from Emacs Dynamic Modules" Eli Zaretskii
2020-10-31 7:36 ` Philipp Stephani
2020-10-31 12:49 ` Stefan Monnier
2020-11-01 20:18 ` Akira Kyle
2020-11-01 20:32 ` Philipp Stephani
2020-11-20 15:54 ` Zhu Zihao
2020-11-20 16:04 ` Robert Pluim
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
List information: https://www.gnu.org/software/emacs/
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=831rhegnde.fsf@gnu.org \
--to=eliz@gnu.org \
--cc=ak@akirakyle.com \
--cc=all_but_last@163.com \
--cc=emacs-devel@gnu.org \
--cc=monnier@iro.umontreal.ca \
--cc=p.stephani2@gmail.com \
--cc=yyoncho@gmail.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
Code repositories for project(s) associated with this public inbox
https://git.savannah.gnu.org/cgit/emacs.git
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).