Messages in this thread | | | Date | Wed, 24 Jun 2020 13:50:46 +0100 | From | Will Deacon <> | Subject | Re: [RFC PATCH] perf/smmuv3: Fix shared interrupt handling |
| |
On Wed, Jun 24, 2020 at 12:48:14PM +0100, Robin Murphy wrote: > On 2020-04-08 17:49, Robin Murphy wrote: > > IRQF_SHARED is dangerous, since it allows other agents to retarget the > > IRQ's affinity without migrating PMU contexts to match, breaking the way > > in which perf manages mutual exclusion for accessing events. Although > > this means it's not realistically possible to support PMU IRQs being > > shared with other drivers, we *can* handle sharing between multiple PMU > > instances with some explicit affinity bookkeeping and manual interrupt > > multiplexing. > > > > RCU helps us handle interrupts efficiently without having to worry about > > fine-grained locking for relatively-theoretical race conditions with the > > probe/remove/CPU hotplug slow paths. The resulting machinery ends up > > looking largely generic, so it should be feasible to factor out with a > > "system PMU" base class for similar multi-instance drivers. > > > > Signed-off-by: Robin Murphy <robin.murphy@arm.com> > > --- > > > > RFC because I don't have the means to test it, and if the general > > approach passes muster then I'd want to tackle the aforementioned > > factoring-out before merging anything anyway. > > Any comments on whether it's worth pursuing this?
Sorry, I don't really get the problem that it's solving. Is there a crash log somewhere I can look at? If all the users of the IRQ are managed by this driver, why is IRQF_SHARED dangerous?
Will
| |