From: Corinna Vinschen <corinna-cygwin@cygwin.com>
To: cygwin@cygwin.com
Subject: Re: uc_sigmask set in a sigaction signal handler not honored
Date: Wed, 03 Apr 2019 12:43:00 -0000 [thread overview]
Message-ID: <20190403124331.GZ3337@calimero.vinschen.de> (raw)
In-Reply-To: <20190403121555.GV3337@calimero.vinschen.de>
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On Apr 3 14:15, Corinna Vinschen wrote:
> On Apr 3 11:27, Petr Skočík wrote:
> > Hi. Correct me if I'm wrong but POSIX appears to define
> >
> > https://pubs.opengroup.org/onlinepubs/7908799/xsh/ucontext.h.html
> >
> > as, among other things, containing the field:
> >
> > sigset_t uc_sigmask the set of signals that are blocked when this
> > context is active
> >
> > and it also specifies that the third argument to a .sa_sigaction
> > signal handler is a ucontext_t* cast to void*.
> >
> > So it should follow that doing
> >
> > void act(int Sig, siginfo_t *Info, void *Uctx)
> > {
> > ucontext_t *uctx = Uctx;
> > sigfillset(&uctx->uc_sigmask);
> > }
> >
> > from a signal handler should alter the signal mask of the thread the
> > signal ran on.
> >
> > This is how Linux and MacOS behave, but not CygWin, as the following
> > program shows:
>
> What you're asking for is really complicated.
>
> The context given to act is the context at the time the signal function
> is called. In Cygwin (lower case w) this is a copy of the context.
>
> sigfillset() has not the faintest clue where this context comes from, it
> just sets the signal mask value without taking any further action.
>
> There are no provisions to control if the called function changes the
> context, other than via setcontext / swapcontext, and I don't see that
> POSIX requires anything else. Both functions change the current
> thread's sigmask according to the value of uc_sigmask.
Or maybe I'm just dumb. Would it suffice if the thread's signal mask is
changed to uc_sigmask when the signal function returns?
Corinna
--
Corinna Vinschen
Cygwin Maintainer
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next prev parent reply other threads:[~2019-04-03 12:43 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-04-03 9:28 Petr Skočík
2019-04-03 12:16 ` Corinna Vinschen
2019-04-03 12:43 ` Corinna Vinschen [this message]
2019-09-09 17:13 ` malloc(0) crashes with SIGABRT Petr Skočík
2019-09-09 18:27 ` malloc(0) crashing " Petr Skočík
2019-09-12 3:59 ` Brian Inglis
2019-09-12 11:33 ` Kaz Kylheku
2019-09-12 18:05 ` Brian Inglis
2019-09-12 17:38 ` Ken Brown
[not found] ` <e20e38ff-49b1-6472-b0a4-faeee0176a7c@gmail.com>
2019-09-13 13:21 ` Ken Brown
2019-04-03 14:39 uc_sigmask set in a sigaction signal handler not honored Petr Skočík
2019-04-03 16:29 ` Corinna Vinschen
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