From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andrew Morton Subject: Re: [Bugme-new] [Bug 14691] New: Complete NAPI IRQ lockup in b44 driver: code fundamentally incompatible with netconsole requirements Date: Wed, 25 Nov 2009 13:16:31 -0800 Message-ID: <20091125131631.46483ce0.akpm@linux-foundation.org> References: Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Cc: bugzilla-daemon@bugzilla.kernel.org, bugme-daemon@bugzilla.kernel.org, netdev@vger.kernel.org, andi@lisas.de To: Gary Zambrano Return-path: Received: from smtp1.linux-foundation.org ([140.211.169.13]:34577 "EHLO smtp1.linux-foundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758099AbZKYVRB (ORCPT ); Wed, 25 Nov 2009 16:17:01 -0500 In-Reply-To: Sender: netdev-owner@vger.kernel.org List-ID: (switched to email. Please respond via emailed reply-to-all, not via the bugzilla web interface). On Wed, 25 Nov 2009 20:15:33 GMT bugzilla-daemon@bugzilla.kernel.org wrote: > http://bugzilla.kernel.org/show_bug.cgi?id=14691 > > Summary: Complete NAPI IRQ lockup in b44 driver: code > fundamentally incompatible with netconsole > requirements > Product: Drivers > Version: 2.5 > Kernel Version: 2.6.32-rc8 > Platform: All > OS/Version: Linux > Tree: Mainline > Status: NEW > Severity: blocking > Priority: P1 > Component: Network > AssignedTo: drivers_network@kernel-bugs.osdl.org > ReportedBy: andi@lisas.de > Regression: No > > > Hi, > > severity "blocking" (== "Blocks development and/or testing work"): it's my > primary window to the world on this router - netconsole - and crashes multiple > times when loading various drivers, thus for me there's no productive > proceeding possible, plus there have been multiple reports on this issue since > at least 2004. > > The kernel version I'm testing it on is 2.6.30.9 (OpenWrt MIPSEL, on ASUS > WL-500gP v2), but since b44 interrupt handler is unchanged I assume it's still > unfixed. > > Frequently when doing some medium activity such as loading modules such as > ftdi_sio, usb_audio etc. (especially with kobject debugging enabled), the > network LED starts blinking like crazy and when re-listening to netconsole > output, there's simply a flood of > %s: Error, poll already scheduled > and the box is DEAD (again! *curse*). > > Productive debugging of multiple USB and ftdi_sio issues is simply impossible > with this kind of problem remaining. > > See also: > "RE:hostname freeze" (2004!!): > http://lists.linuxcoding.com/rhl/2004/msg51048.html > > "b44 driver suspend/resume (was Re: [ACPI] Re: Re: various problems with Acer > TM654, suspend, ACAD, radeon)": > http://osdir.com/ml/network.general/2004-08/msg00208.html > > "acpi and b44: irq disabled, b44: Error, poll already scheduled" (2004!!): > http://lkml.indiana.edu/hypermail/linux/kernel/0408.3/0078.html > > And a very related fix and long discussion is at: > "[PATCH 2.6.30-rc4] r8169: avoid losing MSI interrupts": > http://kerneltrap.org/mailarchive/linux-netdev/2009/5/23/5791863 > > I'm very uncertain whether the interrupt handler method of simply screaming > this error message on every interrupt without doing any actual remedies is a > good idea. > HAH! Now I've got it: the fact that we're on netconsole means that this error > message gets sent _immediately_ (out to the netconsole device!!), thus this > very network transmission encounters an IRQ handler at a time where the > previous scheduled NAPI processing had no chance yet of being done, thus > napi_schedule_prep() FAIL, thus error message again, thus... ad nauseam! > Or, IOW, now I'm _certain_ that it is _NOT_ a good idea to scream this message > on every IRQ without doing anything about it. > > > I want to report this issue now to make sure it can get the attention it > deserves, but for now I'll try to come up with a bandaid locally (simply > silencing the error message) in order to be able to debug the other driver > issues mentioned above. > > Thanks!