Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752984AbZFWJey (ORCPT ); Tue, 23 Jun 2009 05:34:54 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752157AbZFWJep (ORCPT ); Tue, 23 Jun 2009 05:34:45 -0400 Received: from mailout3.samsung.com ([203.254.224.33]:16233 "EHLO mailout3.samsung.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751698AbZFWJep (ORCPT ); Tue, 23 Jun 2009 05:34:45 -0400 Date: Tue, 23 Jun 2009 11:33:35 +0200 From: Marek Szyprowski Subject: RE: PROBLEM: kernel oops with g_serial USB gadget on 2.6.30 In-reply-to: <20090623102129.3b58adbf@lxorguk.ukuu.org.uk> To: "'Alan Cox'" Cc: "'David Brownell'" , "'Alan Stern'" , "'Peter Korsgaard'" , "'USB list'" , "'Kernel development list'" , kyungmin.park@samsung.com Message-id: <002101c9f3e5$b4dc5a10$1e950e30$%szyprowski@samsung.com> MIME-version: 1.0 X-Mailer: Microsoft Office Outlook 12.0 Content-type: text/plain; charset=us-ascii Content-language: pl Content-transfer-encoding: 7BIT Thread-index: Acnz49rBRb1x5B+XSDKJf5RAr5Gd1AAARAtg References: <001201c9f341$20b8b710$622a2530$%szyprowski@samsung.com> <200906222026.51511.david-b@pacbell.net> <001c01c9f3cd$ad02b1d0$07081570$%szyprowski@samsung.com> <200906230022.39040.david-b@pacbell.net> <002001c9f3dd$d7a24df0$86e6e9d0$%szyprowski@samsung.com> <20090623102129.3b58adbf@lxorguk.ukuu.org.uk> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1348 Lines: 39 Hello, On Tuesday, June 23, 2009 11:21 AM, Alan Cox wrote: > > that g_serial driver interacts with tty layer in that packet_done > callback, > > so this is the source of the problems. I noticed that some other UDC > > drivers also does all its job from an interrupt, so they also might > be > > affected. How this bug should be properly resolved? > > Either by not setting ->low_latency or by running the data paths from a > non IRQ context. > > Basically: don't set tty->low_latency if you are handling the > processing > from the IRQ path. The only case low_latency is useful is handling data > from a non-IRQ path where you have latency concerns for tx/rx > switching. I know that, but I wonder how this should be handled in g_serial gadget driver, which might be working on top of both types of low level drivers (doing callback from irq or tasklet). Are there any drawbacks of disabling low_latency mode if callbacks are done from tasklet not from interrupt? If no then the low latency mode should be disabled in g_serial driver. Best regards -- Marek Szyprowski Samsung Poland R&D Center -- 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/