From: Eli Zaretskii <eliz@gnu.org>
To: Lars Ingebrigtsen <larsi@gnus.org>
Cc: emacs-devel@gnu.org
Subject: Re: Asynchronous DNS
Date: Wed, 03 Feb 2016 17:49:23 +0200 [thread overview]
Message-ID: <83k2mlyet8.fsf@gnu.org> (raw)
In-Reply-To: <87k2mmzkry.fsf@gnus.org> (message from Lars Ingebrigtsen on Wed, 03 Feb 2016 11:42:57 +1100)
> From: Lars Ingebrigtsen <larsi@gnus.org>
> Cc: emacs-devel@gnu.org
> Date: Wed, 03 Feb 2016 11:42:57 +1100
>
> > We need to know which code can run on a separate thread, because some
> > things cannot be safely done from any thread but the main
> > (a.k.a. "Lisp") thread. Running the Lisp interpreter is one of them,
> > but it's not the only one. You cannot QUIT or signal an error or do
> > anything else that throws to top-level. You cannot call malloc or
> > free, or any code that does. You cannot modify any data structures
> > visible from Lisp, like buffers, Lisp strings, and the undo list. You
> > cannot access or modify global variables or call any non-reentrant
> > Emacs functions. And there are other no-no's, these are just a few
> > that popped in my mind within the first 5 sec.
>
> Except the malloc thing, that just boils down to "you can't do anything
> Lispy on the other threads" I think?
I don't think "anything Lispy" is a useful definition, since almost
everything we do in Emacs on the C level is "Lispy" in some way. And
a C programmer won't see too many "Lispy" things, I think. E.g., QUIT
just calls longjmp, a standard C function. Many functions that have
potentially long loops call QUIT inside the loop, and you cannot call
those in a non-main thread. Assigning values to a global variable is
standard C practice, but there are some (quite a few, actually)
variables in Emacs which cannot be safely assigned from a non-main
thread, unless you introduce some synchronization mechanism.
> Which nobody has proposed, anyway.
I was just explaining why knowing that we are starting application
threads, and knowing what code these threads can run, is important.
> > However, it sounds like this is all much ado about nothing: I see no
> > references to any threads, old or new, in the changes you made on your
> > feature branch, so is there really anything to discuss here? (I asked
> > the question which led to this sub-thread because you mentioned that
> > you "start a new thread that does getaddrinfo".)
>
> No, I wrote that that's what getaddrinfo_a does, so we could just do
> that ourselves and not have to rely on getaddrinfo_a.
If we introduce such a thread, its code needs to be carefully audited
for the above-mentioned gotchas. E.g., passing to it a C pointer to a
contents of a Lisp string is probably unsafe. It's not rocket science
to DTRT in this case (we already do that quite a lot on MS-Windows),
it just requires very careful programming and code review.
> >> Anyway, this reminds me of something that I've been wondering about gdb
> >> output when running Emacs. It often says something like this:
> >>
> >> warning: Corrupted shared library list: 0x84582e0 != 0x5104c30
> >> warning: Corrupted shared library list: 0x2f172a0 != 0x21688a0
> >> warning: Corrupted shared library list: 0x79f1910 != 0x21688a0
> >> warning: Corrupted shared library list: 0x79f1910 != 0x21688a0
> >> warning: Corrupted shared library list: 0x7a07ae0 != 0x21688a0
> >>
> >> Is that something to be worried about, or is it... normal?
> >
> > It's a real problem. Crystal ball says that some of the system
> > libraries Emacs uses don't have debug info files to match them;
> > instead, you have debug info files from different versions of the
> > libraries. Try "info sharedlibrary" at the GDB prompt, maybe it will
> > tell you which libraries are the offending ones.
>
> Ok, but it's a problem when debugging in gdb, and not a problem for an
> Emacs running without gdb?
Only for the former, AFAIK. GDB is complaining about a data structure
it builds, not about something the executable does.
next prev parent reply other threads:[~2016-02-03 15:49 UTC|newest]
Thread overview: 190+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-01-23 13:50 Asynchronous DNS Lars Magne Ingebrigtsen
2016-01-23 14:56 ` Elias Mårtenson
2016-01-24 21:17 ` Lars Magne Ingebrigtsen
2016-01-25 8:58 ` Elias Mårtenson
2016-01-25 15:51 ` Eli Zaretskii
2016-01-25 17:15 ` Elias Mårtenson
2016-01-25 17:26 ` Eli Zaretskii
2016-01-23 21:42 ` Paul Eggert
2016-01-24 13:53 ` Lars Magne Ingebrigtsen
2016-01-24 14:01 ` Lars Magne Ingebrigtsen
2016-01-24 14:14 ` Lars Magne Ingebrigtsen
2016-01-24 19:58 ` Paul Eggert
2016-01-24 4:49 ` Stefan Monnier
2016-01-24 13:56 ` Lars Magne Ingebrigtsen
2016-01-24 17:16 ` Lars Magne Ingebrigtsen
2016-01-25 2:06 ` Stefan Monnier
2016-01-26 19:48 ` John Wiegley
2016-01-26 22:05 ` Florian Weimer
2016-01-30 0:11 ` Lars Ingebrigtsen
2016-01-30 2:39 ` Alex Dunn
2016-01-30 2:58 ` Lars Ingebrigtsen
2016-01-30 4:11 ` Alex Dunn
2016-01-30 4:34 ` Lars Ingebrigtsen
2016-02-01 3:55 ` Lars Ingebrigtsen
2016-01-30 7:23 ` Eli Zaretskii
2016-01-30 7:46 ` Lars Ingebrigtsen
2016-01-30 8:46 ` Eli Zaretskii
2016-01-30 22:46 ` Lars Ingebrigtsen
2016-01-31 6:12 ` Ken Raeburn
2016-02-01 2:46 ` Lars Ingebrigtsen
2016-01-31 14:03 ` Andy Moreton
2016-02-01 2:08 ` Lars Ingebrigtsen
2016-02-01 2:36 ` Lars Ingebrigtsen
2016-02-01 18:51 ` Eli Zaretskii
2016-02-02 1:15 ` Lars Ingebrigtsen
2016-02-02 3:38 ` Eli Zaretskii
2016-02-02 3:48 ` Lars Ingebrigtsen
2016-02-02 13:25 ` Stefan Monnier
2016-02-02 16:24 ` Eli Zaretskii
2016-02-02 17:11 ` Stefan Monnier
2016-02-02 16:12 ` Eli Zaretskii
2016-02-03 0:42 ` Lars Ingebrigtsen
2016-02-03 15:49 ` Eli Zaretskii [this message]
2016-02-04 2:22 ` Lars Ingebrigtsen
2016-02-04 8:18 ` Alain Schneble
2016-02-04 8:55 ` Lars Ingebrigtsen
2016-02-04 10:13 ` Alain Schneble
2016-02-05 2:08 ` Lars Ingebrigtsen
2016-02-05 7:19 ` Eli Zaretskii
2016-02-05 7:32 ` Lars Ingebrigtsen
2016-02-13 23:47 ` Alain Schneble
2016-02-14 2:22 ` Lars Ingebrigtsen
2016-02-14 11:19 ` Alain Schneble
2016-02-14 16:40 ` Eli Zaretskii
2016-02-16 21:37 ` Alain Schneble
2016-02-20 1:28 ` Lars Ingebrigtsen
2016-02-20 17:55 ` Paul Eggert
2016-02-20 20:18 ` Alain Schneble
2016-02-20 20:33 ` Paul Eggert
2016-02-21 10:29 ` Alain Schneble
2016-02-26 23:54 ` YAMAMOTO Mitsuharu
2016-02-27 3:57 ` Lars Ingebrigtsen
2016-02-27 9:22 ` Alain Schneble
2016-02-28 4:43 ` Lars Ingebrigtsen
2016-02-28 9:44 ` Andreas Schwab
2016-02-29 2:59 ` Lars Ingebrigtsen
2016-02-29 3:30 ` Lars Ingebrigtsen
2016-02-29 8:41 ` Andreas Schwab
2016-02-20 19:31 ` Alain Schneble
2016-02-20 19:57 ` Alain Schneble
2016-02-21 2:36 ` Lars Ingebrigtsen
2016-02-21 3:03 ` Lars Ingebrigtsen
2016-02-21 18:55 ` Alain Schneble
2016-02-21 20:23 ` Eli Zaretskii
2016-02-22 2:15 ` Lars Ingebrigtsen
2016-02-22 3:39 ` Eli Zaretskii
2016-02-22 4:03 ` Lars Ingebrigtsen
2016-02-22 5:45 ` Lars Ingebrigtsen
2016-02-22 2:07 ` Lars Ingebrigtsen
2016-02-24 6:26 ` Lars Ingebrigtsen
2016-02-24 6:29 ` Paul Eggert
2016-02-24 6:52 ` Lars Ingebrigtsen
2016-02-24 8:27 ` John Wiegley
2016-02-21 19:35 ` Alain Schneble
2016-02-22 2:01 ` Lars Ingebrigtsen
2016-02-20 10:57 ` Eli Zaretskii
2016-02-16 2:09 ` Lars Ingebrigtsen
2016-02-05 9:37 ` Alain Schneble
2016-02-04 16:30 ` Eli Zaretskii
2016-02-05 2:31 ` Lars Ingebrigtsen
2016-02-05 7:20 ` Eli Zaretskii
2016-02-03 2:49 ` Lars Ingebrigtsen
2016-02-02 6:41 ` Alain Schneble
2016-02-02 7:06 ` Lars Ingebrigtsen
2016-02-02 7:49 ` Alain Schneble
2016-02-02 21:27 ` Alain Schneble
2016-02-03 0:22 ` Lars Ingebrigtsen
2016-02-03 10:22 ` Yuri Khan
2016-02-04 0:18 ` Lars Ingebrigtsen
2016-02-01 11:58 ` Andy Moreton
2016-02-01 19:10 ` Eli Zaretskii
2016-02-01 22:18 ` Andy Moreton
2016-02-02 1:54 ` Lars Ingebrigtsen
2016-02-02 2:05 ` YAMAMOTO Mitsuharu
2016-02-02 2:18 ` Lars Ingebrigtsen
2016-02-02 3:42 ` Eli Zaretskii
2016-02-03 0:50 ` Lars Ingebrigtsen
2016-02-03 2:43 ` Lars Ingebrigtsen
2016-02-03 15:50 ` Eli Zaretskii
2016-02-04 2:25 ` Lars Ingebrigtsen
2016-02-04 16:31 ` Eli Zaretskii
2016-02-05 2:32 ` Lars Ingebrigtsen
2016-02-05 7:21 ` Eli Zaretskii
2016-02-05 7:33 ` Lars Ingebrigtsen
2016-02-06 7:49 ` Lars Ingebrigtsen
2016-02-06 8:19 ` Eli Zaretskii
2016-02-07 0:34 ` Alain Schneble
2016-02-07 1:38 ` Lars Ingebrigtsen
2016-02-07 11:41 ` Alain Schneble
2016-02-07 19:16 ` Eli Zaretskii
2016-02-07 20:24 ` Alain Schneble
2016-02-08 1:55 ` Lars Ingebrigtsen
2016-02-08 3:40 ` Lars Ingebrigtsen
2016-02-08 7:40 ` Alain Schneble
2016-02-08 7:52 ` Lars Ingebrigtsen
2016-02-08 8:10 ` Alain Schneble
2016-02-09 0:37 ` Lars Ingebrigtsen
2016-02-09 9:02 ` Alain Schneble
2016-02-09 13:46 ` Lars Ingebrigtsen
2016-02-09 17:00 ` Eli Zaretskii
2016-02-09 20:43 ` Alain Schneble
2016-02-09 20:48 ` Eli Zaretskii
2016-02-09 23:22 ` Lars Ingebrigtsen
2016-02-10 10:39 ` Alain Schneble
2016-02-12 2:15 ` Lars Ingebrigtsen
2016-02-12 10:12 ` Alain Schneble
2016-02-13 4:04 ` Lars Ingebrigtsen
2016-02-13 10:16 ` Alain Schneble
2016-02-14 2:20 ` Lars Ingebrigtsen
2016-02-14 5:56 ` Eli Zaretskii
2016-02-14 7:01 ` Lars Ingebrigtsen
2016-02-14 13:56 ` Stefan Monnier
2016-02-15 0:19 ` Alain Schneble
2016-02-15 4:22 ` Lars Ingebrigtsen
2016-02-14 16:32 ` Eli Zaretskii
2016-02-15 0:14 ` Alain Schneble
2016-02-15 3:41 ` Eli Zaretskii
2016-02-15 4:30 ` Lars Ingebrigtsen
2016-02-15 0:02 ` Alain Schneble
2016-02-15 4:39 ` Lars Ingebrigtsen
2016-02-15 6:14 ` Lars Ingebrigtsen
2016-02-15 6:25 ` Lars Ingebrigtsen
2016-02-15 10:55 ` Eli Zaretskii
2016-02-15 12:01 ` Andreas Schwab
2016-02-15 13:50 ` Eli Zaretskii
2016-02-16 2:26 ` Lars Ingebrigtsen
2016-02-15 10:50 ` Eli Zaretskii
2016-02-15 11:06 ` Alain Schneble
2016-02-15 13:49 ` Eli Zaretskii
2016-02-15 15:04 ` Alain Schneble
2016-02-15 16:40 ` Alain Schneble
2016-02-16 2:13 ` Lars Ingebrigtsen
2016-02-16 6:48 ` Alain Schneble
2016-02-15 18:13 ` Alain Schneble
2016-02-12 10:35 ` Andreas Schwab
2016-02-12 11:37 ` Alain Schneble
2016-02-08 18:11 ` Eli Zaretskii
2016-02-09 0:47 ` Lars Ingebrigtsen
2016-02-09 16:56 ` Eli Zaretskii
2016-02-08 10:43 ` Andreas Schwab
2016-02-08 11:55 ` Alain Schneble
2016-02-08 12:55 ` Andreas Schwab
2016-02-08 14:25 ` Alain Schneble
2016-02-08 14:31 ` Andreas Schwab
2016-02-09 0:40 ` Lars Ingebrigtsen
2016-02-09 9:15 ` Alain Schneble
2016-02-09 9:35 ` Alain Schneble
2016-02-07 15:55 ` Eli Zaretskii
2016-02-07 17:45 ` Alain Schneble
2016-02-08 2:03 ` Lars Ingebrigtsen
2016-02-08 15:56 ` John Wiegley
2016-02-08 20:30 ` Rasmus
2016-02-09 0:34 ` Lars Ingebrigtsen
2016-02-08 18:22 ` Eli Zaretskii
2016-02-07 1:35 ` Lars Ingebrigtsen
2016-02-07 16:07 ` Eli Zaretskii
2016-02-08 2:05 ` Lars Ingebrigtsen
2016-02-08 18:20 ` Eli Zaretskii
2016-02-07 17:27 ` John Wiegley
2016-02-08 1:26 ` Lars Ingebrigtsen
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