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Date:      Fri, 8 Mar 2002 00:25:03 -0800
From:      Bill Huey <billh@gnuppy.monkey.org>
To:        Julian Elischer <julian@elischer.org>
Cc:        Nate Williams <nate@yogotech.com>, Poul-Henning Kamp <phk@critter.freebsd.dk>, arch@FreeBSD.ORG
Subject:   Re: Contemplating THIS change to signals. (fwd)
Message-ID:  <20020308082503.GA6690@gnuppy.monkey.org>
In-Reply-To: <Pine.BSF.4.21.0203072354560.46841-100000@InterJet.elischer.org>
References:  <15496.22850.811384.136422@caddis.yogotech.com> <Pine.BSF.4.21.0203072354560.46841-100000@InterJet.elischer.org>

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On Fri, Mar 08, 2002 at 12:08:49AM -0800, Julian Elischer wrote:
> No, it is not really interrupted. It has not been sent back to the
> userland. A STOP certainly doesn't prematurely kill it.
> Its stack still says that it is in the sleep.
> If the SIGCONT occurs, it is still in the sleep where it was before
> an if not, the timeout timer is still running..
> 
> An interrupted sleep is when the timeout is cancelled and control is
> returned so that it goes back towards the userland. This does not 
> happen in a syscall when a SIGSTOP is received.

The way I read it was that both of those things are a kind of notification
to that system call and not literally an interrupt that absolutely must
return it back to userspace some how.

> > 2) Completes, but has a return value such that the userland program can
> >    re-start the system call again.
> 
> This is never the result of a STOP signal detected in msleep(tsleep)

> > In both cases, it has been 'interrupted' (it did not complete as it
> > would had it not received a SIGSTOP signal).
> 
> SIGSTOP does not do this (unless you have set a signal handler for it
> in which ccase it is no longer SIGSTOP but rather something else
> (in fact CAN you set a SIGSTOP handler?)

Don't remember, signals are evil. ;)

bill


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