From mboxrd@z Thu Jan 1 00:00:00 1970 From: Greg KH Subject: Re: XT-PIC interrupts blocked by usbserial ? [Was Re: Intel ICH9M bug : sata unusable with usbserial] Date: Thu, 3 Mar 2011 10:20:47 -0800 Message-ID: <20110303182047.GA28936@kroah.com> References: <20110228151618.GA16322@htj.dyndns.org> <20110228170556.GA29545@frolo.macqel> <20110228173634.GA23008@htj.dyndns.org> <20110228192700.GA3305@kroah.com> <20110301123452.GA1954@frolo.macqel> <20110301141627.GB12881@kroah.com> <20110301150018.GA17827@frolo.macqel> <4D6E477A.9020401@teksavvy.com> <20110303145812.GA3489@frolo.macqel> <4D6FD982.2050308@teksavvy.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from kroah.org ([198.145.64.141]:58575 "EHLO coco.kroah.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758636Ab1CCSYe (ORCPT ); Thu, 3 Mar 2011 13:24:34 -0500 Content-Disposition: inline In-Reply-To: <4D6FD982.2050308@teksavvy.com> Sender: linux-ide-owner@vger.kernel.org List-Id: linux-ide@vger.kernel.org To: Mark Lord Cc: Philippe De Muyter , Tejun Heo , Alan Cox , linux-ide@vger.kernel.org, Greg Kroah-Hartman , linux-usb@vger.kernel.org On Thu, Mar 03, 2011 at 01:10:10PM -0500, Mark Lord wrote: > What is most likely happening here, is that the USB interrupt handler > is returning IRQ_HANDLED under some condition where IRQ_NONE is required. > > In other words, USB thought it got an interrupt, but didn't really, > but since it returns IRQ_HANDLED regardless, then other > device drivers sharing that IRQ don't necessarily get called. > If this happens repeatedly, then it could disrupt the other devices. I doubt this is the issue, as we would have seen it long before now. > Now, that's not overly likely, but then again it's probably not > well tested with everyone using APICs nowadays. > > Or, perhaps the PL2303 driver leaves an interrupt active/pending > without clearing it in hardware, so the interrupt keeps recurring > over and over. This (unlikely) is easy to check for, by watching > the /proc/interrupts count for the USB on your APIC-enabled kernel. A usb driver has no interrupt handling at all, so it just flat out can not do this. It's up to the usb host controller driver, that is what handles interrupts. > If the numbers increase at a phenomenal rate, then there might > be an issue. With an active GPS, one would expect the numbers to > be incrementing steadily, say a few dozen or a hundred or so per second. It all depends on the traffic to the USB device and how well behaved it is, as to how many interrupts it generates. thanks, greg k-h