Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S266626AbUJAUqQ (ORCPT ); Fri, 1 Oct 2004 16:46:16 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S266505AbUJAUli (ORCPT ); Fri, 1 Oct 2004 16:41:38 -0400 Received: from h-68-165-86-241.dllatx37.covad.net ([68.165.86.241]:45649 "EHLO sol.microgate.com") by vger.kernel.org with ESMTP id S263743AbUJAUhK (ORCPT ); Fri, 1 Oct 2004 16:37:10 -0400 Subject: RE: Serial driver hangs From: Paul Fulghum To: Stuart MacDonald Cc: "'Alan Cox'" , "'Russell King'" , "'Roland =?ISO-8859-1?Q?Ca=DFebohm=27?=" , "'Linux Kernel Mailing List'" In-Reply-To: <010101c4a7f3$1ef63540$294b82ce@stuartm> References: <010101c4a7f3$1ef63540$294b82ce@stuartm> Content-Type: text/plain Message-Id: <1096662993.2757.29.camel@deimos.microgate.com> Mime-Version: 1.0 X-Mailer: Ximian Evolution 1.4.6 Date: Fri, 01 Oct 2004 15:36:34 -0500 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1478 Lines: 39 On Fri, 2004-10-01 at 15:13, Stuart MacDonald wrote: > I've come late to this discussion. Not sure what the scope of this > cleanup is, but I'd like to see the flip buffers done away with > entirely, to be replaced by a single buffer with proper r/w locking. > Or keep the flip arrangement, but move it out of tty_struct so that it > can be made larger. Some of our high speed products find the rx buffer > to be less than sufficient. This started as a bug report of a lockup under high load. (2 ports @ 921600bps) The cause was serial.c (kernel 2.4) not clearing the receive IRQ if the flip buffer was full. The ISR simply returned without flushing the receive FIFO or disabling receive interrupts. The short term cure for the lock up is to flush the receive FIFO and discard the data. The discussion then descended into analysis of the flip buffer scheme in general. Everyone seems to agree it should be eliminated or replaced. It has synchronization problems for SMP. Alan is busy reworking other tty locking issues, and it probably annoyed by the noise created by this thread :-) I suspect when those issues are resovled there will be an opportunity to submit suggestions and patches. -- Paul Fulghum paulkf@microgate.com - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/