From: Eli Zaretskii <eliz@gnu.org>
To: "Gerd Möllmann" <gerd.moellmann@gmail.com>
Cc: pipcet@protonmail.com, yantar92@posteo.net, emacs-devel@gnu.org,
eller.helmut@gmail.com
Subject: Re: MPS: a random backtrace while toying with gdb
Date: Sun, 30 Jun 2024 09:16:00 +0300 [thread overview]
Message-ID: <86tthbgdlr.fsf@gnu.org> (raw)
In-Reply-To: <m2frsv2dvh.fsf@pro2.fritz.box> (message from Gerd Möllmann on Sun, 30 Jun 2024 07:33:54 +0200)
> From: Gerd Möllmann <gerd.moellmann@gmail.com>
> Cc: pipcet@protonmail.com, yantar92@posteo.net, emacs-devel@gnu.org,
> eller.helmut@gmail.com
> Date: Sun, 30 Jun 2024 07:33:54 +0200
>
> Eli Zaretskii <eliz@gnu.org> writes:
>
> >> Indeed
> >>
> >> #10 0x0000555555827385 in PSEUDOVECTORP (a=XIL(0x7fffeb90875d), code=9) at /home/yantar92/Git/emacs/src/lisp.h:1105
> >> #11 PROCESSP (a=XIL(0x7fffeb90875d)) at /home/yantar92/Git/emacs/src/process.h:212
> >> #12 XPROCESS (a=XIL(0x7fffeb90875d)) at /home/yantar92/Git/emacs/src/process.h:224
> >> #13 handle_child_signal (sig=sig@entry=17) at process.c:7660
> >>
> >> Someone has an idea what to do with that?
> >
> > Call sigblock at the beginning of dflt_scan (and friends) and
> > sigunblock before it returns?
>
> Yuk.
Why "yuck"? That's a valid solution, IMO, especially if there are no
better ones. I'm talking about blocking only a small number of
signals: SIGCHLD, SIGPROF, SIGALRM, and maybe also SIGIO and SIGINT.
(We should also consider SIGUSR1 and SIGUSR2.)
> > Are there any guidance in the MPS docs for handling such signals in
> > these situations? If not, can we ask them for guidance? It is
> > unrealistic to expect any real-life program to do nothing in signal
> > handlers except setting flags. And even flags could be subject to MPS
> > moving GC, at least in some cases. So there must be some way of
> > dealing with that in a safe way.
>
> It's Emacs' fault. MPS cannot reasonably be expected to assume that a
> client program uses MPS managed memory in a signal handler. My 2 cents.
That's unreasonable, IMNSHO. Programs manage memory for various
purposes, and nothing in principle should prevent a program from
accessing MPS-managed memory from a signal handler.
Are you saying that a program that manages _all_ of its heap-allocated
memory via MPS cannot also handle signals in a safe way?
> >> And maybe how to reproduce?
> >
> > Run for enough time with subprocesses that start and terminate, I
> > guess?
>
> Just remembered that I won't be able to reproduce this anyway an macOS,
> where barriers don't use signals.
AFAIU, this scenario is not necessarily related to barrier-related
signals. SIGCHLD caused us to access MPS-managed memory, which
violated some assertion in MPS, because the arena lock was already
taken.
next prev parent reply other threads:[~2024-06-30 6:16 UTC|newest]
Thread overview: 68+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-06-29 19:12 MPS: a random backtrace while toying with gdb Ihor Radchenko
2024-06-29 19:19 ` Pip Cet
2024-06-29 21:46 ` Gerd Möllmann
2024-06-30 4:55 ` Eli Zaretskii
2024-06-30 5:33 ` Gerd Möllmann
2024-06-30 6:16 ` Eli Zaretskii [this message]
2024-06-30 6:43 ` Gerd Möllmann
2024-06-30 8:52 ` Eli Zaretskii
2024-06-30 9:43 ` Gerd Möllmann
2024-06-30 10:05 ` Eli Zaretskii
2024-06-30 11:20 ` Gerd Möllmann
2024-06-30 12:16 ` Eli Zaretskii
2024-06-30 12:43 ` Gerd Möllmann
2024-06-30 9:36 ` Helmut Eller
2024-06-30 10:00 ` Eli Zaretskii
2024-06-30 10:24 ` Helmut Eller
2024-06-30 10:43 ` Eli Zaretskii
2024-06-30 18:42 ` Helmut Eller
2024-06-30 18:59 ` Gerd Möllmann
2024-06-30 19:25 ` Pip Cet
2024-06-30 19:49 ` Ihor Radchenko
2024-06-30 20:09 ` Eli Zaretskii
2024-06-30 20:32 ` Pip Cet
2024-07-01 11:07 ` Eli Zaretskii
2024-07-01 17:27 ` Pip Cet
2024-07-01 17:42 ` Ihor Radchenko
2024-07-01 18:08 ` Eli Zaretskii
2024-07-02 7:55 ` Pip Cet
2024-07-02 13:10 ` Eli Zaretskii
2024-07-02 14:24 ` Pip Cet
2024-07-02 14:57 ` Eli Zaretskii
2024-07-02 17:06 ` Pip Cet
2024-07-03 11:31 ` Pip Cet
2024-07-03 11:50 ` Eli Zaretskii
2024-07-03 14:35 ` Pip Cet
2024-07-03 15:41 ` Eli Zaretskii
2024-07-01 2:33 ` Eli Zaretskii
2024-07-01 6:05 ` Helmut Eller
2024-06-30 19:58 ` Eli Zaretskii
2024-06-30 21:08 ` Ihor Radchenko
2024-07-01 2:35 ` Eli Zaretskii
2024-07-01 11:13 ` Eli Zaretskii
2024-07-01 11:47 ` Ihor Radchenko
2024-07-01 12:33 ` Eli Zaretskii
2024-07-01 17:17 ` Ihor Radchenko
2024-07-01 17:44 ` Eli Zaretskii
2024-07-01 18:01 ` Ihor Radchenko
2024-07-01 18:16 ` Eli Zaretskii
2024-07-01 18:24 ` Ihor Radchenko
2024-07-01 18:31 ` Eli Zaretskii
2024-07-01 18:51 ` Ihor Radchenko
2024-07-01 19:05 ` Eli Zaretskii
2024-07-01 19:34 ` Gerd Möllmann
2024-07-01 20:00 ` Ihor Radchenko
2024-07-02 4:33 ` Gerd Möllmann
2024-07-02 7:05 ` Ihor Radchenko
2024-07-02 7:06 ` Gerd Möllmann
2024-07-01 18:19 ` Gerd Möllmann
2024-07-01 18:23 ` Eli Zaretskii
2024-06-30 11:07 ` Gerd Möllmann
2024-06-30 11:06 ` Gerd Möllmann
2024-06-30 11:05 ` Gerd Möllmann
2024-06-30 9:59 ` Pip Cet
2024-06-30 10:09 ` Eli Zaretskii
2024-06-30 10:16 ` Pip Cet
2024-06-30 10:34 ` Eli Zaretskii
2024-06-30 13:06 ` Pip Cet
2024-06-30 11:10 ` Gerd Möllmann
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