On Sun, 3 Oct 2010, Eric W. Biederman wrote: > Thomas Gleixner <tglx@xxxxxxxxxxxxx> writes: > >> 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. Oh well. I said that it's not a requirement to remove the lookup from the entry code, but we can remove it for optimizaiton reasons. That is the same problem vs. migration as we have a reference to irq_desc either by lookup or by storage in vector data on x86. > >> 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... No, I'm not renaming it. I'm cleaning up the mess which was created with references to irq_desc all over the place. I need to change core code and I cant w/o breaking the world and some more, just because everyone fiddles in irq_desc directly. So I want to hand down irq_data which is right now inside of irq_desc until the irq_desc users outside of kernel/irq are gone. Then irq_data is not necessarily a part of irq_desc anymore. > 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. I tend to disagree. The sparse_irq optimizations to get rid of the redundant irq_desc lookups to gain access to the irq_data should have been done in exactly that way. And I call something which removes 500 lines of code hardly useless code churn. > 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. This could have been done 2 years ago by those who pushed sparse_irq including the resulting "optimization". Thanks, tglx -- 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
