From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S262111AbUKJTk7 (ORCPT ); Wed, 10 Nov 2004 14:40:59 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S262114AbUKJTk7 (ORCPT ); Wed, 10 Nov 2004 14:40:59 -0500 Received: from clock-tower.bc.nu ([81.2.110.250]:64977 "EHLO localhost.localdomain") by vger.kernel.org with ESMTP id S262111AbUKJTi5 (ORCPT ); Wed, 10 Nov 2004 14:38:57 -0500 Subject: Re: 2.4 virtual terminal timing From: Alan Cox To: Tom Schouten Cc: Linux Kernel Mailing List In-Reply-To: <20041110125828.GB15767@zzz.i> References: <20041110125828.GB15767@zzz.i> Content-Type: text/plain Content-Transfer-Encoding: 7bit Message-Id: <1100111756.20556.21.camel@localhost.localdomain> Mime-Version: 1.0 X-Mailer: Ximian Evolution 1.4.6 (1.4.6-2) Date: Wed, 10 Nov 2004 18:35:58 +0000 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Mer, 2004-11-10 at 12:58, Tom Schouten wrote: > i am trying to find out if there is a direct path in 2.4.x from > keyboard interrupt, through console/tty stuff to process wakeup, > for a 2 thread process with one thread blocking on tty read, > running SCHED_FIFO, or a single thread process with async IO. > You hit the keyboard. A microcontroller with a brain the size of a pea sits around for a bit works out what you hit and we get an interrupt. After that it sends it slowly over a serial link to the PC. The tty driver figures out the characters and sends them down to the line discipline layer. The line discipline will wake the user process from that event. At least in 2.6 the tty driver isn't doing batching for keyboard commands that I can see so it ought to be reasonably quick.