Date:	Tue, 10 Oct 2006 17:18:27 -0600
From:	ebiederm@...ssion.com (Eric W. Biederman)
To:	Jeremy Fitzhardinge <jeremy@...p.org>
Cc:	linux-thinkpad@...ux-thinkpad.org, linux-kernel@...r.kernel.org,
	"Brown, Len" <len.brown@...el.com>, acpi-devel@...nel.org,
	Pavel Machek <pavel@...e.cz>, Andrew Morton <akpm@...l.org>
Subject: Re: X60s w/t kern 2.6.19-rc1-git: two BUG warnings

Jeremy Fitzhardinge <jeremy@...p.org> writes:

> Martin Lorenz wrote:
>> Dear kernel gurus,
>>
>
> (CC:s added to various interested parties.)
>
>> whatever I do and whic problem I seem to get fixed new ones arise:
>>
>> now I loose ACPI events after suspend/resume. not every time, but roughly 3
>> out of 4 times.
>>
>
> Yes, I'm seeing this as well.  It used to be a 100% failure, so there has been
> some improvement.  On the other hand, before that it used to work perfectly...
> Unfortunately I don't have a good feeling for when these changes happened.

So the first symptom is not the failure in e1000 open but this.
[ 6727.082000] Trying to free already-free IRQ 20
Which I suspect comes from e1000_close as it happens after
the e1000 watchdog timer goes off because it hasn't gotten
interrupts for a while.

We have other bits of suspicious code as well.
The e1000 rolls it's own version of pci_save_state but doesn't
call any of the msi save/restore state routines.

The bug is from the attempt to allocate an already allocated irq.
So it appears somehow in the save/restore mess the msi code
thought the irq code was allocates but the irq code did not?

I have scratched the msi code enough lately that something may have
shaken loose.   In particular in commit: 
d7bd007e480672c99d8656c7b7b12ef0549432c37 I explicitly disallowed some
weird double allocation/deallocation code that could have masked this
problem.  

The e1000 watchdog doesn't seem to be going off in the functioning
case so that may not be it.

My problem is I have been given two incomplete dmesg traces one
that works and one that doesn't and without any background in this
area beyond noting the e1000 watchdog timer is firing I can't say what
happened.

In the working cases do you have trouble if you up and down the
network interface?

We seem to be at that nasty interface layer where every piece is
making assumptions about how someone else's piece works, and someone
has their assumptions wrong.

If someone who understands the how suspend/resume is supposed to work
for these kinds of things can speak up that would help.

>
>> the only errornous things I see in the logs are those:
>>
>> [ 6727.089000] BUG: warning at drivers/pci/msi.c:680/pci_enable_msi()
>> [ 6727.089000]  [<c0103bd9>] dump_trace+0x69/0x1af
>> [ 6727.089000]  [<c0103d37>] show_trace_log_lvl+0x18/0x2c
>> [ 6727.089000]  [<c01043d6>] show_trace+0xf/0x11
>> [ 6727.089000]  [<c01044d9>] dump_stack+0x15/0x17
>> [ 6727.089000]  [<c0208cd6>] pci_enable_msi+0x78/0x22e
>> [ 6727.090000]  [<c0257fe5>] e1000_open+0x64/0x176
>> [ 6727.091000]  [<c029b121>] dev_open+0x2b/0x62
>> [ 6727.092000]  [<c0299c2f>] dev_change_flags+0x47/0xe4
>> [ 6727.093000]  [<c02cdceb>] devinet_ioctl+0x252/0x556
>> [ 6727.094000]  [<c0290e9a>] sock_ioctl+0x19e/0x1c2
>> [ 6727.095000]  [<c016979b>] do_ioctl+0x1f/0x62
>> [ 6727.095000]  [<c0169a23>] vfs_ioctl+0x245/0x257
>> [ 6727.096000]  [<c0169a81>] sys_ioctl+0x4c/0x67
>> [ 6727.096000]  [<c0102dc3>] syscall_call+0x7/0xb
>> [ 6727.096000] DWARF2 unwinder stuck at syscall_call+0x7/0xb
>> [ 6727.096000]
>> [ 6727.096000] Leftover inexact backtrace:
>> [ 6727.096000]
>> [ 6727.096000]  [<c02e007b>] unix_stream_connect+0x15b/0x367
>> [ 6727.096000]  =======================
>>
>> which occurs in variations but very often
>>
>
> This just seems to be something thinking the IRQ isn't MSI-capable.  It doesn't
> seem to have any negative effect - the e1000 works fine anyway.

It is a BUG.  The first symptoms of which where the failure to free
the irq in by the e1000 watchdog.  The normal irq code said you didn't
have an irq handler registered for that irq.  

Does anyone know how the irq handler could go aways in the weird
suspend/resume world?

>> [ 6708.389000] e1000: eth0: e1000_watchdog: NIC Link is Up 100 Mbps Full
> Duplex
>> [ 6708.389000] e1000: eth0: e1000_watchdog: 10/100 speed: disabling TSO
>> [ 6727.082000] Trying to free already-free IRQ 20
>> [ 6727.089000] BUG: warning at drivers/pci/msi.c:680/pci_enable_msi()
>> [ 6727.089000]  [<c0103bd9>] dump_trace+0x69/0x1af
>> [ 6727.089000]  [<c0103d37>] show_trace_log_lvl+0x18/0x2c
>> [ 6727.089000]  [<c01043d6>] show_trace+0xf/0x11
>> [ 6727.089000]  [<c01044d9>] dump_stack+0x15/0x17
>> [ 6727.089000]  [<c0208cd6>] pci_enable_msi+0x78/0x22e
>> [ 6727.090000]  [<c0257fe5>] e1000_open+0x64/0x176
>> [ 6727.091000]  [<c029b121>] dev_open+0x2b/0x62
>> [ 6727.092000]  [<c0299c2f>] dev_change_flags+0x47/0xe4
>> [ 6727.093000]  [<c02cdceb>] devinet_ioctl+0x252/0x556
>> [ 6727.094000]  [<c0290e9a>] sock_ioctl+0x19e/0x1c2
>> [ 6727.095000]  [<c016979b>] do_ioctl+0x1f/0x62
>> [ 6727.095000]  [<c0169a23>] vfs_ioctl+0x245/0x257
>> [ 6727.096000]  [<c0169a81>] sys_ioctl+0x4c/0x67
>> [ 6727.096000]  [<c0102dc3>] syscall_call+0x7/0xb
>> [ 6727.096000] DWARF2 unwinder stuck at syscall_call+0x7/0xb
>> [ 6727.096000] [ 6727.096000] Leftover inexact backtrace:
>> [ 6727.096000] [ 6727.096000]  [<c02e007b>] unix_stream_connect+0x15b/0x367
>> [ 6727.096000]  =======================
>> [ 6728.719000] e1000: eth0: e1000_watchdog: NIC Link is Up 100 Mbps Full
> Duplex
>> [ 6728.719000] e1000: eth0: e1000_watchdog: 10/100 speed: disabling
>TSO

Eric
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