Re: SATA resume slowness, e1000 MSI warning

Kok, Auke
2007-03-07T16:31:16Z

Eric W. Biederman wrote:
> "Kok, Auke" <auke-jan.h.kok@intel.com> writes:
>
>> Ingo Molnar wrote:
>>> * Kok, Auke <auke-jan.h.kok@intel.com> wrote:
>>>
>>>>>> BUG: at drivers/pci/msi.c:611 pci_enable_msi()
>>>>> I would poke Eric Biederman(sp?) about this one. Maybe its even solved by
>>>>> the MSI-enable-related patch he posted in the past 24-48 hours.
>>>> I tried the 3-patch series "[PATCH 0/3] Basic msi bug fixes.." and they fix
>>>> this problem for me. Were you expecting the OOPS in the first place? [...]
>>> the bug was the warning message (a WARN_ON()) above - not an oops. So that
>>> warning message is gone in your testing?
>> yes.
>
> Sorry for the slow delay. I was out of town for my brothers wedding the last few
> days.
>
> I wasn't exactly expecting the WARN_ON to trigger. What I fixed was
> an inconsistency in handling our state bits. Fixing that
> inconsistency appears to have fixed the e1000 usage scenario mostly by
> accident.
>
> The basic issue is that pci_save_state saves the current msi state
> along with other registers, and then the e1000 driver goes and
> disables the msi irq after we have saved the irq state as on.
>
> My code notices that the msi irq was disabled before restore time, so
> it skips the restore. However we now have a leak of the msi saved cap
> because we are not freeing it.
>
> This leaves with some basic questions.
> - Does it make sense for suspend/resume methods to request/free irqs?
> - Does it make sense for suspend/resume methods to allocate/free msi irqs?
> - Do we want pci_save/restore_cap to save/restore msi state?
>
> The path of least resistance is to just free the extra state and we
> are good. I'm just not quite certain that is sane and it has been a
> long day.

we used to have a lengthy e1000_pci_save|restore_state in our code, which is now
gone, so I'm all for that. A separate pci_save_pxie|msi(x)_state for every
driver seems completely unnecessary. I can't think of a use case where
saving+restoring everything hurts. That's what you want I presume.

We currently free all irq's and msi before going into suspend in e1000, and I
think that is probably a good thing, somehow I can think of bad things happening
if we dont, but I admit that I haven't tried it without alloc/free. We do this
in e100 as well and it works.

Another motivation would be to leave this up to the driver: if the driver
chooses to free/alloc interrupts because it makes sense, you probably would want
to keep that choice available. Devices that don't need this can skip the
alloc/free, but leave the choice open for others.

hth

Auke