> 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. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
