From: Sergey Bugaev <bugaevc@gmail.com>
To: Florian Weimer <fweimer@redhat.com>
Cc: libc-alpha@sourceware.org, bug-hurd <bug-hurd@gnu.org>,
Samuel Thibault <samuel.thibault@gnu.org>
Subject: Re: __pthread_setcancelstate called unconditionally, crashes at 0
Date: Thu, 11 May 2023 21:00:14 +0300 [thread overview]
Message-ID: <CAN9u=Hfw6iF1wWAQ-4ST8OeM3O9t+f1KGfidgn+NJXX1Zo_7Xw@mail.gmail.com> (raw)
In-Reply-To: <87ilcyg3ud.fsf@oldenburg3.str.redhat.com>
On Thu, May 11, 2023 at 8:44 PM Florian Weimer <fweimer@redhat.com> wrote:
> Apparently, Hurd does not support async cancellation? Then
> __pthread_setcancelstate never has to unwind, so you just turn it into a
> non-weak symbol.
It does in theory, htl/pt-cancel.c has a PTHREAD_CANCEL_ASYNCHRONOUS
branch that calls into sysdeps/mach/hurd/htl/pt-docancel.c, which
manipulates the victim thread's state to make it call __pthread_exit
(0). (This is also implemented in a rather sad way that most likely
wouldn't work on x86_64-gnu; I'll get to fixing that some time...)
But it doesn't seem to either do any unwinding, nor is
__pthread_setcancelstate async-cancel-safe (it uses a mutex).
> If you need async cancellation support, the core cancellation routine
> could be made weak, so that it is linked into the executable only if
> pthread_cancel is ever called.
Could you please expand on how this all (unwinding, async
cancellation) is relevant? Clearly calling error () in a
PTHREAD_CANCEL_ASYNCHRONOUS context is undefined behavior since error
() is not async-cancel-safe.
Sergey
next prev parent reply other threads:[~2023-05-11 18:00 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-05-11 17:31 Sergey Bugaev
2023-05-11 17:44 ` Florian Weimer
2023-05-11 17:52 ` Samuel Thibault
2023-05-11 17:56 ` Florian Weimer
2023-05-11 18:00 ` Sergey Bugaev [this message]
2023-05-11 18:12 ` Florian Weimer
2023-05-11 18:28 ` Sergey Bugaev
2023-05-11 18:35 ` Florian Weimer
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