Messages in this thread | | | Date | Wed, 24 Aug 2011 14:16:43 -0400 | From | Don Zickus <> | Subject | Re: [RFC][PATCH 2/6] x86, nmi: create new NMI handler routines |
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On Wed, Aug 24, 2011 at 07:51:00PM +0200, Peter Zijlstra wrote: > On Wed, 2011-08-24 at 13:44 -0400, Don Zickus wrote: > > > > + rcu_read_lock(); > > > > + a = rcu_dereference_raw(*ap); > > > > > > The reason for rcu_dereference_raw() is to prevent lockdep from choking > > > due to being called from an NMI handler, correct? If so, please add a > > > comment to this effect on this and similar uses. > > > > That sounds right. But honestly, I just copied what notifier_call_chain > > had. Regardless, I will make sure to document that in my next version. > > Thanks! > > Not quite right, nmi_enter() does lockdep_disable() and makes > lock_is_held() return always true. > > I think this (and the other sites) could do with rcu_dereference_check(, > lockdep_is_held(&desc->lock)); not that it wouldn't be anything but > documentation since the actual test isn't working from NMI context but I > do think its worth it for that alone.
So you want me to remove the _raw part of the dereference? I can test that with lockdep enabled to verify things don't go splat.
Cheers, Don
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