On Thu, Jul 16, 2015 at 10:51:25AM +0100, Daniel Thompson wrote: > On 16/07/15 10:37, Russell King - ARM Linux wrote: > >That can be implemented in the arch raise() method if needed - most > >architectures shouldn't need it as if they are properly raising a NMI > >which is, by definition, deliverable with normal IRQs disabled. > > Agreed. The bug certainly could be fixed in the ARM raise() function. > > However I'm still curious whether there is any architecture that benefits > from forcing the current CPU into an NMI handler? Why doesn't the > don't-run-unnecessary-code argument apply here as well?
The benefit is that we get a consistent way of invoking the backtrace, since causing the NMI exception gives us a 'struct pt_regs' to work with, which we wouldn't otherwise have if we tried to call it "inline". The NMI backtrace includes dumping the register state of the NMI- receiving CPUs, which needs a 'struct pt_regs' and generating a that in arch-independent code wouldn't be nice. In any case, if this area needs changing in the generic code, it should be done as a separate change so that it can be properly assessed and validated on x86. In the mean time, I will action Thomas' request to put it into my tree so that we can get some reasonable linux-next time with it, and hopefully have some progress towards FIQ-based backtracing for ARM. Thanks. -- FTTC broadband for 0.8mile line: currently at 10.5Mbps down 400kbps up according to speedtest.net. -- 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/
