John, ----- Ursprüngliche Mail ----- >>> The line was previously synchronized for the kmsg_dump_get_line() >>> call. But yes, it was not synchronized after the call, which is a bug if >>> the dump is triggered on multiple CPUs simultaneously. The commit >>> message should also mention that it is handling that bug. >>> >>>> IMHO, this patch is not needed. >>> >>> I am not familiar enough with ARCH=um to know if dumps can be triggered >>> on multiple CPUs simultaneously. Perhaps ThomasM or Richard can chime in >>> here. >> >> Well, uml has no SMP support, so no parallel dumps. :-) > > When I grep through arch/um, I see many uses of spinlocks. This would > imply that uml at least has some sort of preemption model where they are > needed. Dumps can trigger from any context and from multiple paths. > > If you are sure that this is no concern, then I will drop this patch > from my series.
Currently uml selects ARCH_NO_PREEMPT, so no preemtion too. We have spinlocks at obvious places in arch/um/ just to be ready if uml supports SMP at some point. Does your patch have drawbacks right now for uml? If not, I'd suggest to keep it. Thanks, //richard
