> I have read this thread and I concluded few things:
>
> 1) It is impossible to know that the card won't send more interrupts:
> Even if I do a read from the device, the IRQ can be pending in the bus/APIC
> It is even possible (and likely) that the IRQ line will be shared, thus the
> handler can be called by non-relevant device.
>
> 2) the synchronize_irq(); in .suspend is useless:
> an IRQ can happen immediately after this synchronize_irq();
> and interrupt even the .suspend()
> (At least theoretically)
It's not totally useless not. It guarantees that by the time your
are out of your suspend(), a simultaneous instance of the IRQ handler
is either finished, or it (or any subsequent occurence) have seen
your insuspend flag set to 1.
> Thus I now understand that .suspend() should do:
>
> saa_writel(SAA7134_IRQ1, 0);
> saa_writel(SAA7134_IRQ2, 0);
> saa_writel(SAA7134_MAIN_CTRL, 0);
>
> dev->insuspend = 1;
> smp_wmb();
>
> /* at that point the _request to disable card's IRQs was issued, we don't know
> that there will be no irqs anymore.
> the smp_mb(); guaranties that the IRQ handler will bail out in that case. */
>
> /* .......*/
>
> pci_save_state(pci_dev);
> pci_set_power_state(pci_dev, pci_choose_state(pci_dev, state));
> return 0;
The above doesn't handle the case where the IRQ handle just passed the
if (insuspend) test. You may end up calling pci_set_power_state() while
in the middle of some further HW accesses in the handler.
You still need synchronize_irq() for that reason. Or use a spinlock.
> and the interrupt handler:
>
> smp_rmb();
> if (dev->insuspend)
> goto out;
>
> Am I right?
Not quite :-)
Also not that the work we are doing with synchronize_irq, if it gets
merged, renders it unnecessary for you to add those two memory barriers,
synchronize_irq will pretty much do the ordering for you.
Cheers,
Ben.
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