On Wed, 13 May 2015 13:17:06 +0530 Shreyas B Prabhu <[email protected]> wrote:
> >>> + TP_CONDITION(cpu_online(smp_processor_id())), > >> > >> Are we sure these can't generate check_preemption_disabled() warnings? > >> Is there some reason why all these calls always occur with preemption > >> disabled? > > > > Good catch. I don't think the code does. > > > > Now, I'm not sure if we should just add a raw_smp_processor_id(). The > > idea is just to make sure that the CPU we are running on is online, > > because it is possible to call theses trace points when the CPU is > > going offline. If that happens, then there's a race with RCU. > > > > Since a task can not be migrated to an offline CPU, we don't need to > > worry about the cpu_online(smp_processor_id()) returning a false > > positive. A false negative would just skip a tracepoint, but I'm not > > sure that is possible either. > > > > In any case, comments should also be added to why the condition is > > there. > > > I'll send a patch adding the comments. Please also confirm that these tracepoints cannot be called from preemptible contexts. Or switch to raw_smp_processor_id(). -- 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/
