Messages in this thread | | | Date | Wed, 13 May 2015 13:17:06 +0530 | From | Shreyas B Prabhu <> | Subject | Re: [PATCH RESEND 0/3] tracing/mm: Fix suspicious rcu_dereference_check() usage warnings |
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On Wednesday 13 May 2015 02:24 AM, Steven Rostedt wrote: > On Tue, 12 May 2015 13:36:01 -0700 > Andrew Morton <akpm@linux-foundation.org> wrote: > >> On Tue, 12 May 2015 16:03:51 -0400 Steven Rostedt <rostedt@goodmis.org> wrote: >> >>> On Tue, 12 May 2015 12:59:26 +0530 >>> Shreyas B Prabhu <shreyas@linux.vnet.ibm.com> wrote: >>> >>>> Hi Steven, >>>> On closer look, there is no particular maintainer who picks changes to >>>> this file. Can you please pick these up? >>> >>> Perhaps Andrew Morton? >>> >>> No problem, I can take these too. >>> >> >> I grabbed them, thanks. >>
Thanks Andrew.
>>> + 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.
Thanks, Shreyas
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