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Date:   Wed, 12 Jun 2019 11:41:08 +0200
From:   Pavel Machek <pavel@denx.de>
To:     Arseny Maslennikov <ar@cs.msu.ru>
Cc:     Pavel Machek <pavel@denx.de>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Jiri Slaby <jslaby@suse.com>, Ingo Molnar <mingo@redhat.com>,
        Peter Zijlstra <peterz@infradead.org>,
        linux-kernel@vger.kernel.org,
        "Vladimir D . Seleznev" <vseleznv@altlinux.org>
Subject: Re: [PATCH 0/7] TTY Keyboard Status Request
Message-ID: <20190612094108.GA11439@amd>
References: <20190605081906.28938-1-ar@cs.msu.ru>
 <20190609174139.GA11944@xo-6d-61-c0.localdomain>
 <20190609194013.GA3736@cello>
 <20190609195132.GA1430@amd>
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Hi!

> > > If any of isig, icanon and iexten is disabled on the tty, the signal =
is
> > > not sent.
> >=20
> > As expected.
> >=20
> > > Any application that wants to handle raw terminal input events itself,
> > > e.g. vim, mutt, libreadline, anything ncurses-based, etc., has to turn
> > > off the tty's cooked mode, i.e. at least icanon. This means those
> > > applications are unaffected.
> >=20
> > Agreed, those are unaffected.
> >=20
> > But if I have an application doing read() from console (without
> > manipulating tty), am I going to get surprise signal when user types
> > ^T?
> >=20
> > 	     	      	      	     	      	     	       	     Pavel
>=20
> As of now, that application will indeed receive a signal that is
> guaranteed to be ignored by default.
>=20
> This is similar to SIGWINCH, which is default-ignored as well: if the
> terminal width/height changes (like when a terminal emulator window is
> resized), its foreground pgrp gets a surprise signal as well, and the
> processes that don't care about WINCH (and thus have default
> disposition) do not get confused.
> E.g. 'strace cat' demonstrates this quite clearly.

Ok, so this should be safe as long as noone listens for SIGPWR. So
=2E.. I guess we are ok :-).
								Pavel


--=20
DENX Software Engineering GmbH,      Managing Director: Wolfgang Denk
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany

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