From: Alan Cox <alan@lxorguk.ukuu.org.uk>
To: Thomas Pfaff <tpfaff@pcs.com>
Cc: linux-kernel@vger.kernel.org
Subject: Re: Question about TTY_DO_WRITE_WAKEUP
Date: Thu, 20 Nov 2008 14:31:47 +0000 [thread overview]
Message-ID: <20081120143147.5e8d6c20@lxorguk.ukuu.org.uk> (raw)
In-Reply-To: <Pine.LNX.4.64.0811201446380.21561@lxtpfaff.pcs.ditec.de>
> Is the TTY_DO_WRITE_WAKEUP bit some kind of cruft that can be removed entirely
> or should i generate a patch for serial devices only ?
It shouldn't happen at the serial level. The line discipline sets the
flag as and when it has data for the process above.
The expected flow in normal use is
app writes to tty
data goes to n_tty ldisc
goes to tty
n_tty ldisc seems tty blocked
n_tty ldisc sets DO_WRITE_WAKEUP
tty gets ucongested
calls n_tty write_wakeup
SIGIO sent
Flag set again
The important part of the logic is in n_tty.c and tty_io.c
Alan
next prev parent reply other threads:[~2008-11-20 14:32 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-11-20 10:06 Thomas Pfaff
2008-11-20 13:17 ` Alan Cox
2008-11-20 14:09 ` Thomas Pfaff
2008-11-20 14:31 ` Alan Cox [this message]
2008-11-20 15:12 ` Thomas Pfaff
2008-11-20 15:55 ` Alan Cox
2008-11-20 16:39 ` Thomas Pfaff
2008-11-20 16:47 ` Alan Cox
2008-11-20 16:58 ` Alan Cox
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