On Sun, Oct 06, 2013 at 05:19:46PM +1100, Benjamin Herrenschmidt wrote: > On Sun, 2013-10-06 at 08:02 +0200, Alexander Gordeev wrote: > > In fact, in the current design to address the quota race decently the > > drivers would have to protect the *loop* to prevent the quota change > > between a pci_enable_msix() returned a positive number and the the next > > call to pci_enable_msix() with that number. Is it doable? > > I am not advocating for the current design, simply saying that your > proposal doesn't address this issue while Ben's does. There is one major flaw in min-max approach - the generic MSI layer will have to take decisions on exact number of MSIs to request, not device drivers. This will never work for all devices, because there might be specific requirements which are not covered by the min-max. That is what Ben described "...say, any even number within a certain range". Ben suggests to leave the existing loop scheme to cover such devices, which I think is not right. What about introducing pci_lock_msi() and pci_unlock_msi() and let device drivers care about their ranges and specifics in race-safe manner? I do not call to introduce it right now (since it appears pSeries has not been hitting the race for years) just as a possible alternative to Ben's proposal. -- Regards, Alexander Gordeev agordeev@xxxxxxxxxx -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
