From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S263166AbVGNWis (ORCPT ); Thu, 14 Jul 2005 18:38:48 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S262881AbVGNWgQ (ORCPT ); Thu, 14 Jul 2005 18:36:16 -0400 Received: from taxbrain.com ([64.162.14.3]:9523 "EHLO petzent.com") by vger.kernel.org with ESMTP id S263164AbVGNWfR (ORCPT ); Thu, 14 Jul 2005 18:35:17 -0400 From: "karl malbrain" To: "Russell King" Cc: "Linux-Kernel@Vger. Kernel. Org" Subject: RE: 2.6.9: serial_core: uart_open Date: Thu, 14 Jul 2005 15:35:07 -0700 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit X-Priority: 3 (Normal) X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook IMO, Build 9.0.6604 (9.0.2911.0) X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1441 Importance: Normal In-Reply-To: <20050714195717.B10410@flint.arm.linux.org.uk> X-Spam-Processed: petzent.com, Thu, 14 Jul 2005 15:31:22 -0700 (not processed: message from valid local sender) X-Return-Path: karl@petzent.com X-MDaemon-Deliver-To: linux-kernel@vger.kernel.org X-MDAV-Processed: petzent.com, Thu, 14 Jul 2005 15:31:27 -0700 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org > -----Original Message----- > From: Russell King > Sent: Thursday, July 14, 2005 11:57 AM > To: karl malbrain > Cc: Linux-Kernel@Vger. Kernel. Org > Subject: Re: 2.6.9: serial_core: uart_open > > > On Thu, Jul 14, 2005 at 10:16:23AM -0700, karl malbrain wrote: > > I'd love to do a ps listing for you, but, except for the mouse, > the system > > is completely unresponsive after issuing the blocking open("/dev/ttyS1", > > O_RDRW). > > > > Telnet is dead; the console will respond to the mouse, but the > only thing I > > can do is close the xterm window and thereby kill the process. > I can launch > > a new xterm window from the menu using the mouse, but the new > window is dead > > and has no cursor nor bash prompt. > > > > The clock on the display is being updated. After several hours > the system > > reboots on its own. > > > > I recall from my DOS days that 8250/16550 programming requires that the > > specific IIR source be responded to, or the chip will immediately > > turn-around with another interrupt. It doesn't look like 8250.c is > > organized to respond directly to the modem-status-change value > in IIR which > > requires reading MSR to reset. > > Well, at this point interrupts are enabled, and _are_ handled. The > only thing we use the IIR for is to answer the question "did this > device say it had an interrupt?" > > If it did, we unconditionally read the MSR without fail. > > So, I've no idea what so ever about what's going on here. I don't > understand why your system is behaving the way it is. Therefore, > I don't think we can progress this any further, sorry. AT LAST I HAVE SOME DATA!!! The problem is that ALL SYSTEM CALLS to open "/dev/tty" are blocking!! even with O_NDELAY set and even from completely disjoint sessions. I discovered this via issuing "strace sh". That's why the new xterm windows froze. The original process doing the open("/dev/ttyS1", O_RDWR) is listed in the ps aux listing as status S+. Hope this helps.... karl m