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Date: Wed, 4 Mar 2015 13:19:52 +0100
From: Corinna Vinschen <corinna-cygwin@cygwin.com>
To: cygwin@cygwin.com
Subject: Re: Cygwin hangs up if several keys are typed during outputting a lot of texts.
Message-ID: <20150304121952.GL3213@calimero.vinschen.de>
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References: <20150228144019.0e4cfdb3a26bfac361b538e2@nifty.ne.jp> <20150228140251.GA11124@calimero.vinschen.de> <20150302204502.39b3e03ad5084b0b5add5d10@nifty.ne.jp> <20150302144426.GK3213@calimero.vinschen.de> <20150304203407.14008531b0fb63ad5c19a33f@nifty.ne.jp>
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On Mar  4 20:34, Takashi Yano wrote:
> On Mon, 2 Mar 2015 15:44:26 +0100
> Corinna Vinschen <corinna-cygwin@cygwin.com> wrote:
>=20
> > > 1) Buffer of named pipe gets full-filled by a lot of data written
> > >   by slave side.
> > > 2) WriteFile() in fhandler_pty_master::doecho(), which is called
> > >   from master side by key input, is blocked because the buffer
> > >   is full.
> > > 3) If a handling to read from the pipe is in the same thread as
> > >   key input, the thread falls into deadlock.
> > >=20
> > > To check buffer space before WriteFile() is one idea,
> > > but it is not smart, I suppose...
> >=20
> > I think that's not it.  For testing I added code to convert the
> > WriteFile calls in fhandler_pty_slave::write, fhandler_pty_master::doec=
ho
> > and fhandler_pty_slave::write to overlapped I/O and made sure to wait
> > for the result after the output mutex has been released.
> >=20
> > This change has no effect at all.  Looks like this needs some more
> > digging.
>=20
> Hmm.
>=20
> To confirm my assumption, I have modified the TTY code
> for testing. The modification is shown in an attached
> diff-file against current CVS version. (Note that this
> patch is not for fixing the problem. It is for just a
> testing.)
>=20
> With this modification, half of buffer is kept empty
> for fhandler_pty_master::doecho(). I assumed the blocking
> could be avoided because buffer is always free.
>=20
> As a result of the test, it has become clear that this
> modification conceals the problem. This means the problem
> is closely related to occupancy of buffer.
>=20
> Now, I suppose the cause has been clarified. So we have
> to work out a solution. How can we resolve this problem?

I'm not sure.  I still have to look deeper into that.  Locally
I treid to woraround this problem by calling WriteFile overlapped
without waiting for the result, but even that doesn't work.

Hmm,
Corinna

--=20
Corinna Vinschen                  Please, send mails regarding Cygwin to
Cygwin Maintainer                 cygwin AT cygwin DOT com
Red Hat

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