From: Helmut Eller <eller.helmut@gmail.com>
To: Paul Eggert <eggert@cs.ucla.edu>
Cc: "Eli Zaretskii" <eliz@gnu.org>,
"Gerd Möllmann" <gerd.moellmann@gmail.com>,
emacs-devel@gnu.org
Subject: Re: MPS signals and Emacs
Date: Mon, 22 Apr 2024 16:10:00 +0200 [thread overview]
Message-ID: <87edaxlc93.fsf@gmail.com> (raw)
In-Reply-To: <71431fc4-2ab2-4778-88df-25d4e315d737@cs.ucla.edu> (Paul Eggert's message of "Sun, 21 Apr 2024 23:44:10 -0700")
On Sun, Apr 21 2024, Paul Eggert wrote:
[..]
> Emacs's SIGBUS and SIGSEGV handlers are used only deal with serious
> internal fatal errors, which should never happen, and if they do
> happen I hope MPS will do the right thing with them by passing them to
> Emacs's thread_fatal_action. You should test that by injecting a
> serious internal fatal error (usage of a bad pointer) into Emacs and
> seeing that MPS does the right thing with it.
The code and the comment around line 100 in protsigx.c[*] suggests that
MPS is trying to do the right thing by invoking the previously installed
handler with:
kill(getpid(), PROT_SIGNAL);
Where PROT_SIGNAL=SIGSEGV. As the comment there explains, this does not
pass along the siginfo_t. That of course means, that the previously
installed handler can't do much other than aborting (si_code will be 0).
I verified that this works, i.e. handle_sigsegv is actually called after
sigHandle when accessing address 0x4.
Whether this makes any sense in a multi-threaded setup; well, I'm not so
sure.
For the moment it's probably good enough but it will likely make
debugging bugs that aren't GC-related a bit harder. In GDB it's already
necessary to say something like
handle SIGSEGV nostop pass print
so that the process doesn't stop every time a memory barrier is hit.
I was also puzzled by the fact that during pdump, sigHandle worked fine
but later during loaddefs-gen not. I then found this comment in
init_signals:
/* Don't alter signal handlers if dumping. On some machines,
changing signal handlers sets static data that would make signals
fail to work right when the dumped Emacs is run. */
if (will_dump_p ())
return;
That explains the puzzling behavior but it makes me wonder what kind of
machine that could possibly be. Also MPS clearly has to install memory
barriers, will_dump_p or not. Will that affect those machines?
Helmut
[*] https://github.com/Ravenbrook/mps/blob/master/code/protsgix.c
next prev parent reply other threads:[~2024-04-22 14:10 UTC|newest]
Thread overview: 149+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-04-20 9:34 STatus of MPS branch Gerd Möllmann
2024-04-20 14:56 ` Michael Albinus
2024-04-20 15:08 ` Gerd Möllmann
2024-04-20 15:32 ` Michael Albinus
2024-04-20 17:37 ` Gerd Möllmann
2024-04-21 7:39 ` Michael Albinus
2024-04-21 7:56 ` Gerd Möllmann
2024-04-21 8:00 ` Gerd Möllmann
2024-04-21 8:04 ` Michael Albinus
2024-04-21 8:08 ` Gerd Möllmann
2024-04-21 8:18 ` Michael Albinus
2024-04-21 8:28 ` Gerd Möllmann
2024-04-21 8:17 ` Gerd Möllmann
2024-04-21 9:43 ` Michael Albinus
2024-04-21 10:07 ` Gerd Möllmann
2024-04-21 10:58 ` Tramp tests in MPS branch (was: STatus of MPS branch) Michael Albinus
2024-04-21 12:44 ` Tramp tests in MPS branch Gerd Möllmann
2024-04-21 9:29 ` STatus of " Eli Zaretskii
2024-04-21 4:38 ` Gerd Möllmann
2024-04-21 5:31 ` Eli Zaretskii
2024-04-21 5:39 ` Gerd Möllmann
2024-04-21 9:04 ` Eli Zaretskii
2024-04-21 9:17 ` Gerd Möllmann
2024-04-21 6:15 ` Gerd Möllmann
2024-04-21 9:09 ` Eglot tests on MPS branch (was: STatus of MPS branch) Eli Zaretskii
2024-04-21 9:53 ` João Távora
2024-04-21 10:13 ` Eglot tests on MPS branch Gerd Möllmann
2024-04-21 11:01 ` João Távora
2024-04-21 10:55 ` Eglot tests on MPS branch (was: STatus of MPS branch) Eli Zaretskii
2024-04-21 7:49 ` STatus of MPS branch Gerd Möllmann
2024-04-21 8:45 ` Gerd Möllmann
2024-04-21 9:08 ` Andrea Corallo
2024-04-21 9:33 ` Native compilation on " Eli Zaretskii
2024-04-21 10:17 ` Gerd Möllmann
2024-04-21 13:07 ` Andrea Corallo
2024-04-22 7:15 ` Gerd Möllmann
2024-04-22 22:02 ` Andrea Corallo
2024-04-23 3:11 ` Gerd Möllmann
2024-04-23 16:09 ` Gerd Möllmann
2024-04-23 19:43 ` Andrea Corallo
2024-04-24 12:49 ` Gerd Möllmann
2024-04-24 18:14 ` Andrea Corallo
2024-04-24 18:28 ` Gerd Möllmann
2024-04-24 20:54 ` Andrea Corallo
2024-04-25 4:33 ` Gerd Möllmann
2024-04-25 5:50 ` Andrea Corallo
2024-04-25 7:18 ` Gerd Möllmann
2024-04-25 8:06 ` Andrea Corallo
2024-04-25 8:15 ` Gerd Möllmann
2024-04-25 8:57 ` Gerd Möllmann
2024-04-25 9:42 ` Andrea Corallo
2024-04-25 11:33 ` Gerd Möllmann
2024-04-25 5:24 ` Eli Zaretskii
2024-04-25 5:48 ` Andrea Corallo
2024-04-25 15:20 ` Eli Zaretskii
2024-04-26 10:15 ` Gerd Möllmann
2024-04-21 8:58 ` STatus of " Andrea Corallo
2024-04-21 9:19 ` Gerd Möllmann
2024-04-21 9:30 ` Native compilation on MPS branch (was: STatus of MPS branch) Eli Zaretskii
2024-04-21 14:39 ` STatus of MPS branch Helmut Eller
2024-04-21 15:37 ` Gerd Möllmann
2024-04-21 15:52 ` Eli Zaretskii
2024-04-21 20:24 ` Helmut Eller
2024-04-22 4:58 ` Gerd Möllmann
2024-04-22 5:28 ` Gerd Möllmann
2024-04-22 6:15 ` MPS signals and Emacs (was: STatus of MPS branch) Eli Zaretskii
2024-04-22 6:44 ` MPS signals and Emacs Paul Eggert
2024-04-22 7:19 ` Gerd Möllmann
2024-04-22 7:40 ` Paul Eggert
2024-04-22 7:49 ` Gerd Möllmann
2024-04-22 8:09 ` Eli Zaretskii
2024-04-22 8:27 ` Gerd Möllmann
2024-04-22 8:55 ` Eli Zaretskii
2024-04-22 9:02 ` Mattias Engdegård
2024-04-22 9:02 ` Gerd Möllmann
2024-04-22 9:18 ` Eli Zaretskii
2024-04-22 9:29 ` Gerd Möllmann
2024-04-22 9:41 ` Eli Zaretskii
2024-04-22 10:22 ` Gerd Möllmann
2024-04-22 10:46 ` Eli Zaretskii
2024-04-22 11:00 ` Gerd Möllmann
2024-04-22 12:01 ` Eli Zaretskii
2024-04-22 12:16 ` Gerd Möllmann
2024-04-22 10:54 ` Eli Zaretskii
2024-04-22 11:05 ` Gerd Möllmann
2024-04-22 19:41 ` Paul Eggert
2024-04-22 20:55 ` Gerd Möllmann
2024-04-22 22:12 ` Paul Eggert
2024-04-23 3:15 ` Gerd Möllmann
[not found] ` <87le54g1h2.fsf@dick>
2024-04-23 5:51 ` Gerd Möllmann
2024-04-23 6:35 ` Helmut Eller
2024-04-23 6:45 ` Gerd Möllmann
2024-04-23 6:53 ` Helmut Eller
2024-04-23 14:29 ` Gerd Möllmann
[not found] ` <87sezbsmsd.fsf@dick>
2024-04-24 5:03 ` Gerd Möllmann
2024-04-22 7:46 ` Eli Zaretskii
2024-04-22 7:55 ` Gerd Möllmann
2024-04-22 14:10 ` Helmut Eller [this message]
2024-04-22 14:42 ` Eli Zaretskii
2024-04-22 22:06 ` Paul Eggert
2024-04-23 7:04 ` Eli Zaretskii
2024-04-22 5:36 ` STatus of MPS branch Gerd Möllmann
2024-04-22 5:50 ` Gerd Möllmann
2024-04-22 15:09 ` Helmut Eller
2024-04-22 17:02 ` Gerd Möllmann
2024-04-24 7:26 ` Collecting markers with MPS (was: STatus of MPS branch) Helmut Eller
2024-04-24 7:44 ` Eli Zaretskii
2024-04-24 8:56 ` Collecting markers with MPS Helmut Eller
2024-04-24 9:17 ` Gerd Möllmann
2024-04-24 10:22 ` Eli Zaretskii
2024-04-24 10:27 ` Gerd Möllmann
2024-04-24 10:58 ` Gerd Möllmann
2024-04-24 13:32 ` Eli Zaretskii
2024-04-24 13:51 ` Gerd Möllmann
2024-04-24 15:03 ` Helmut Eller
2024-04-24 15:54 ` Eli Zaretskii
2024-04-24 16:21 ` Helmut Eller
2024-04-24 16:26 ` Eli Zaretskii
2024-04-24 16:50 ` Gerd Möllmann
2024-04-24 19:18 ` Helmut Eller
2024-04-24 19:55 ` Gerd Möllmann
2024-04-25 7:38 ` Mattias Engdegård
2024-04-24 9:08 ` Gerd Möllmann
2024-04-24 19:03 ` Helmut Eller
2024-04-24 20:02 ` Gerd Möllmann
2024-04-24 20:13 ` Helmut Eller
2024-04-24 20:42 ` Gerd Möllmann
2024-04-25 9:44 ` Helmut Eller
2024-04-25 11:44 ` Gerd Möllmann
2024-04-25 16:04 ` basic questions on MPS Andrea Corallo
2024-04-25 17:51 ` Helmut Eller
2024-04-25 18:48 ` Eli Zaretskii
2024-04-25 18:53 ` Gerd Möllmann
2024-04-25 19:26 ` Vibhav Pant
2024-04-26 6:36 ` Helmut Eller
2024-04-26 7:25 ` Gerd Möllmann
2024-04-26 15:07 ` vibhavp
2024-04-26 6:42 ` Gerd Möllmann
2024-04-27 0:20 ` Richard Stallman
2024-04-27 8:41 ` Helmut Eller
2024-04-28 22:44 ` Richard Stallman
2024-04-29 4:27 ` Helmut Eller
2024-04-29 22:40 ` Richard Stallman
2024-04-25 18:41 ` Eli Zaretskii
2024-04-25 18:53 ` Andrea Corallo
2024-04-25 18:56 ` Gerd Möllmann
2024-04-25 19:29 ` Andrea Corallo
2024-04-25 19:03 ` Eli Zaretskii
2024-04-25 19:09 ` Andrea Corallo
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