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From: ebiederm@xmission.com (Eric W. Biederman)
To: Andrew Morton <akpm@osdl.org>
Cc: Martin Lorenz <martin@lorenz.eu.org>,
       Jesse Brandeburg <jesse.brandeburg@gmail.com>,
       linux-kernel@vger.kernel.org
Subject: Re: un/shared IRQ problem (was: Re: 2.6.18 - another DWARF2)
References: <20061017063710.GA27139@gimli>
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Date: Thu, 19 Oct 2006 08:48:10 -0600
In-Reply-To: <20061019000109.626170f7.akpm@osdl.org> (Andrew Morton's message
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Andrew Morton <akpm@osdl.org> writes:

> On Thu, 19 Oct 2006 08:39:21 +0200
> Martin Lorenz <martin@lorenz.eu.org> wrote:
>
>> On Wed, Oct 18, 2006 at 11:26:03PM -0700, Andrew Morton wrote:
>> > On Wed, 18 Oct 2006 08:34:31 +0200
>> > Martin Lorenz <martin@lorenz.eu.org> wrote:
>> > 
>> > > On Tue, Oct 17, 2006 at 11:52:16AM -0700, Jesse Brandeburg wrote:
>> > > > On 10/16/06, Martin Lorenz <martin@lorenz.eu.org> wrote:
>> > > > >just got the following on resume:
>> > > > >
>> > > > >[87026.706000]  [<c0251745>] e1000_open+0xcd/0x1a4
>> > > > >[87026.714000] DWARF2 unwinder stuck at syscall_call+0x7/0xb
>> > > > >[87026.715000] Leftover inexact backtrace:
>> > > > >[87026.715000] e1000: eth0: e1000_request_irq: Unable to allocate
> interrupt
>> > > > >Error: -16
>> > > > 
>> > > > I'm pretty sure this isn't an e1000 problem.  you need to talk to
>> > > > whoever is maintaining the IRQ subsystem for x86.  E1000 is attempting
>> > > > to register a shared interrupt and someone has already registered that
>> > > > interrupt unshared.
>> > > 
>> > > interestingly though it always involves e1000 when I see dumps like this.
>> > > I already reported more of those :-)
>> > > this one dosen't seem to do any harm to system stability. it occurs on
> every
>> > > suspend/resume and I can circumvent it by disabling msi
>> > > 
>> > > > 
>> > > > looks like several devices are sharing IRQ 201 (aka GSI 16) and ahci
>> > > > or usb uhci_hcd is likely the problem, or the (acpi) power management
>> > > > subsystem.
>> > > > 
>> > > > Hope this helps get the right people involved.
>> > > 
>> > > thank you
>> > 
>> > Could we see the /proc/interrupts please, so we can find out where the
>> > clash is happening?
>> 
>> 
>> here you are
>> 
>> ~# cat /proc/interrupts
>>            CPU0       CPU1
>>   0:   76521957    2009390    IO-APIC-edge  timer
>>   1:      39599          0    IO-APIC-edge  i8042
>>   8:        128          0    IO-APIC-edge  rtc
>>   9:     415044          0   IO-APIC-level  acpi
>>  12:     862451          0    IO-APIC-edge  i8042
>>  58:      68014     326850         PCI-MSI  libata
>>  66:     508910      17187   IO-APIC-level  sdhci:slot0, uhci_hcd:usb3
>> 74: 3156375 0 IO-APIC-level uhci_hcd:usb2, ohci1394, HDA Intel
>>  82:     134828          0   IO-APIC-level  uhci_hcd:usb4, ehci_hcd:usb5
>>  90:      46548          0         PCI-MSI  eth0
>> 201: 100133 0 IO-APIC-level uhci_hcd:usb1, yenta, i915@pci:0000:00:02.0
>> NMI:          0          0
>> LOC:   78530935   78520308
>> ERR:          0
>> MIS:          0
>> 
>
> There are already three interrupt sources on 201, so they are all happy to
> share.
>
> It's e1000.  Jesse, you fibbed ;)
>
> static int e1000_request_irq(struct e1000_adapter *adapter)
> {
> 	...
> 	if (adapter->have_msi)
> 		flags &= ~IRQF_SHARED;

Well MSI irqs can't be shared, as they are edged triggered.
Is the e1000 really trying to use irq 201?   That would indicate
a logic failure in the msi irq allocator.  It should never allocate
an inuse irq.

I have to ask what is the state in 2.6.19-rc2? I'm wondering if
my turning of the msi irq allocator inside out has fixed this problem.

Does this situation work if MSI is disabled, in 2.6.18?

The backwards msi irq allocator in 2.6.18 is so convoluted it may have
a corner case where it fails, and that is triggering this mess.

If 2.6.19 works with MSI's enabled and 2.6.18 works with MSI disabled
I'm inclined to say I have done all that is reasonable.

Eric

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