Re: [BUG] msr-trace.h:42 suspicious rcu_dereference_check() usage!

From: Peter Zijlstra <peterz@infradead.org>
To: Jiri Olsa <jolsa@redhat.com>
Cc: Steven Rostedt <rostedt@goodmis.org>,
	"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
	linux-kernel@vger.kernel.org, Ingo Molnar <mingo@kernel.org>,
	Josh Triplett <josh@joshtriplett.org>,
	Andi Kleen <andi@firstfloor.org>,
	Jan Stancek <jstancek@redhat.com>, Borislav Petkov <bp@alien8.de>,
	Thomas Gleixner <tglx@linutronix.de>
Subject: Re: [BUG] msr-trace.h:42 suspicious rcu_dereference_check() usage!
Date: Thu, 23 Feb 2017 18:28:01 +0100	[thread overview]
Message-ID: <20170223172801.GH6515@twins.programming.kicks-ass.net> (raw)
In-Reply-To: <20170223122434.GA20127@krava>

On Thu, Feb 23, 2017 at 01:24:34PM +0100, Jiri Olsa wrote:
> On Mon, Nov 21, 2016 at 10:28:50AM +0100, Peter Zijlstra wrote:
> > 
> > I think I prefer something like the below, that only annotates the one
> > RDMSR in question, instead of all of them.
> > 
> > 
> > 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 think Boris and Thomas were talking about moving the entire c1e
detection out of there.