linux-kernel - Re: [BUG] msr-trace.h:42 suspicious rcu_dereference

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Message-ID: <20170223171109.GZ26852@two.firstfloor.org>
Date:   Thu, 23 Feb 2017 09:11:10 -0800
From:   Andi Kleen <andi@...stfloor.org>
To:     Jiri Olsa <jolsa@...hat.com>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
        linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...nel.org>,
        Josh Triplett <josh@...htriplett.org>,
        Andi Kleen <andi@...stfloor.org>,
        Jan Stancek <jstancek@...hat.com>
Subject: Re: [BUG] msr-trace.h:42 suspicious rcu_dereference_check() usage!

> > diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
> > index 0888a879120f..d6c6aa80675f 100644
> > --- a/arch/x86/kernel/process.c
> > +++ b/arch/x86/kernel/process.c
> > @@ -357,7 +357,7 @@ static void amd_e400_idle(void)
> >  	if (!amd_e400_c1e_detected) {
> >  		u32 lo, hi;
> >  
> > -		rdmsr(MSR_K8_INT_PENDING_MSG, lo, hi);
> > +		RCU_NONIDLE(rdmsr(MSR_K8_INT_PENDING_MSG, lo, hi));
> >  
> >  		if (lo & K8_INTP_C1E_ACTIVE_MASK) {
> >  			amd_e400_c1e_detected = true;
> 
> hum, I might have missed some other solution in discussion,
> and can't see this one being pulled in.. should I resend this?

I suppose you could also use the new notrace msr variant.

BTW this check is quite annoying.

-Andi