Thomas Gleixner <tglx@xxxxxxxxxxxxx> writes: > On Sun, 3 Oct 2010, Eric W. Biederman wrote: >> Thomas Gleixner <tglx@xxxxxxxxxxxxx> writes: >> > Rationale: >> > ---------- >> > >> > The current sparse_irq allocator has several short comings due to >> > failures in the design or the lack of it: >> > >> > - Requires iteration over the number of active irqs to find a free slot >> > Some architectures have grown their own workarounds for this. >> > >> > - Freeing of irq descriptors is not possible >> > >> > - Racy between create_irq_nr and destroy_irq plugged by horrible >> > callbacks >> > >> > - Migration of active irq descriptors is not possible >> >> I believe you have distored the design when aiming for migration >> of active irq descriptors (which you have not even implemented yet). >> >> How do you plan to remove the radix tree lookup from the irq >> handling path? > > Not at all and it's not even even a requirement to remove the lookup > for implementing live migration. It sounds like it is a requirement to *keep* the lookup for supporting live migration. *Keeping* the lookup I see as a serious problem. If we do this right the only users of the radix tree will be drivers using the functions in interrupt.h. >> Those files provide the genirq irq chip implementation especially >> drivers/pci/msi.c. Of course they will do what every other irq_chip >> implementation does to get access to data. There is an unpleasant >> difference between which generic irq data field htirq.c uses and msi.c >> which may be worth cleaning up. But otherwise I don't see any >> fundamental problems. > > The fundamental problem I hit, was the hack which handed down irq_desc > to avoid the lookup. If it had been msi_desc in the first place, then > I would not even need to touch the msi code to cleanup x86. Just because you intend to rename the irq_desc irq_data... It isn't a hack for an irq method to look at irq_desc. At least not until your irq_data changes go through. This has nothing to do with how x86 is structured and everything to do with your irq_data ``cleanup'' which appears to be mostly about code churn, for very little apparent benefit. In the current state of the kernel I find it very hard to swallow that having a genirq client using irq_desc (which is the only way to implement somethings) is a hack. Eric -- To unsubscribe from this list: send the line "unsubscribe linux-arch" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
