Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755812AbYHUGD6 (ORCPT ); Thu, 21 Aug 2008 02:03:58 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753115AbYHUGDs (ORCPT ); Thu, 21 Aug 2008 02:03:48 -0400 Received: from de01egw02.freescale.net ([192.88.165.103]:51516 "EHLO de01egw02.freescale.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751477AbYHUGDr (ORCPT ); Thu, 21 Aug 2008 02:03:47 -0400 X-MimeOLE: Produced By Microsoft Exchange V6.5 Content-class: urn:content-classes:message MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Subject: Serial of guest kernel complain "too much work" in kvm/qemu Date: Thu, 21 Aug 2008 14:03:56 +0800 Message-ID: X-MS-Has-Attach: X-MS-TNEF-Correlator: Thread-Topic: Serial of guest kernel complain "too much work" in kvm/qemu Thread-Index: AckDU7J/HvRMarWYTA+3GrWdHsuICw== From: "Liu Yu" To: , , , Cc: "Hollis Blanchard" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: 8bit X-MIME-Autoconverted: from base64 to 8bit by alpha id m7L642dq024492 Content-Length: 1266 Lines: 34 Hi all, How is this going? http://www.archivum.info/qemu-devel@nongnu.org/2008-02/msg00169.html I use serial as guest's default stdio on powerpc platform. When displaying a number of characters, e.g. cat a big ascii file, the serial always hangs as it encounters overwhelming interrupts, and then complains "serial8250: too much work for irq 42". The problem is that: serial in qemu generate an interrupt on every output character, while Linux driver reads serial data in a loop but gives up after a fixed number (256) of iterations. So if serial output more than 256 characters in a short time, the serial die. I had to use the patch below to get it worked around. So what is the best way to solve it? --- diff --git a/drivers/serial/8250.c b/drivers/serial/8250.c index be95e55..af3e569 100644 --- a/drivers/serial/8250.c +++ b/drivers/serial/8250.c @@ -70,7 +70,7 @@ static unsigned int nr_uarts = CONFIG_SERIAL_8250_RUNTIME_UARTS; #define DEBUG_INTR(fmt...) do { } while (0) #endif -#define PASS_LIMIT 256 +#define PASS_LIMIT 65536 /* * We default to IRQ0 for the "no irq" hack. Some ????{.n?+???????+%?????ݶ??w??{.n?+????{??G?????{ay?ʇڙ?,j??f???h?????????z_??(?階?ݢj"???m??????G????????????&???~???iO???z??v?^?m???? ????????I?