Re: SATA resume slowness, e1000 MSI warning

[Kok, Auke]

Kok, Auke wrote:
> Eric W. Biederman wrote:
> > "Kok, Auke" <auke-jan.h.kok@xxxxxxxxx> writes:
> >
> > > Ingo Molnar wrote:
> > > > * Kok, Auke <auke-jan.h.kok@xxxxxxxxx> 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.

ah, looking at the code in e1000 we do:

_suspend:
	pci_save_state();
	free_irq()

_resume:
	pci_restore_state();
	alloc_irq();

I suppose that's not good either, and the major cause of the warning in the 
first place.

Maybe I can rollback your latest patches and try to fix that mess by postponing 
the pci_save_state until after we free'd the irq's.

Auke
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