Messages in this thread | | | Subject | Re: Reworking suspend-resume sequence (was: Re: PCI PM: Restore standard config registers of all devices early) | From | Benjamin Herrenschmidt <> | Date | Wed, 04 Feb 2009 08:02:56 +1100 |
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On Tue, 2009-02-03 at 18:04 +0100, Rafael J. Wysocki wrote:
> > Now, there's one subtle problem with resume in this picture. Namely, before > > running the "early resume of devices" we have to make sure that the interrupts > > will be masked. However, masking MSI-X, for example, means writing into > > the memory space of the device, so we can't do it at this point. Of course, we > > can assume that MSI/MSI-X will be masked when we get control from the BIOS > > (moreover, they are not shareable, so we can just ignore them at this point), > > but still we'll have to mask the other interrupts before doing the > > local_irq_enable() on resume - marked by the (*) above. This appears to be > > doable, though.
Which is why I prefer making mutex/semaphores/allocations "safe" to use in that late suspend phase with IRQs off.
It sounds like a less invasive thing, simpler, change, allowing to move the ACPI stuff back to where it belongs, and it would help solving other problems such as the problems I exposed with video resume, which I'm trying to do -very- early (ie, before sysdev's even).
In fact, as I may have said elsewhere, I'm also being bitten by the PCI layer doing kmalloc(...GFP_KERNEL) all over the place nowadays including in things like pci_get_device() which are hurting some memory controller code I have that runs in late suspend (I could refactor that code to do the pci_get_* earlier, it's just one more thing..).
> Having reconsidered it, I think that the "loop of disable_irq()" may be > problematic due to MSI/MSI-X and devices that are put into D3 during the > "normal" suspend. That is, we shouldn't try to mask MSI/MSI-X for devices in > D3 (especially MSI-X, since that involves writing to the device's memory > space). This implies that devices in D3 should be avoided in the "loop of > disable_irq()", but that could be tricky if we loop over struct irq_desc > objects. > > Still, we can modify pci_pm_suspend() (and the other PCI callbacks analogously) > so that it masks the interrupt of the device right before returning to the > caller if the device has not been put into a low power state before. After > that all devices will either be in low power states, so they won't be able to > generate interrupts, or have their interrupts masked. In the latter case the > core can then put them into low power states in suspend_late().
That's going to be hard to get right vs. shared interrupts no ?
I think the "other" solution overall is much more simple.
Cheers, Ben.
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