From: "Liang, Kan" <kan.liang@intel.com>
To: Andi Kleen <andi@firstfloor.org>,
        Peter Zijlstra <peterz@infradead.org>
CC: Jiri Olsa <jolsa@kernel.org>, Vince Weaver <vince@deater.net>,
        "Robert Richter" <rric@kernel.org>,
        lkml <linux-kernel@vger.kernel.org>, Ingo Molnar <mingo@kernel.org>
Subject: RE: [PATCH] perf/x86: Fix overlap counter scheduling bug
Thread-Topic: [PATCH] perf/x86: Fix overlap counter scheduling bug
Thread-Index: AQHSOdIsiqKg0s6PyEOKEiPKy1JRqqDPPNCQ
Date: Tue, 8 Nov 2016 16:22:13 +0000
Message-ID: <37D7C6CF3E00A74B8858931C1DB2F07750C8D9D0@SHSMSX103.ccr.corp.intel.com>
References: <1478015068-14052-1-git-send-email-jolsa@kernel.org>
 <20161108122039.GP3142@twins.programming.kicks-ass.net>
 <20161108150949.GM26852@two.firstfloor.org>
In-Reply-To: <20161108150949.GM26852@two.firstfloor.org>
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> >
> >
> > diff --git a/arch/x86/events/intel/uncore_snbep.c
> > b/arch/x86/events/intel/uncore_snbep.c
> > index 272427700d48..71bc348736bd 100644
> > --- a/arch/x86/events/intel/uncore_snbep.c
> > +++ b/arch/x86/events/intel/uncore_snbep.c
> > @@ -669,7 +669,7 @@ static struct event_constraint
> snbep_uncore_cbox_constraints[] = {
> >  	UNCORE_EVENT_CONSTRAINT(0x1c, 0xc),
> >  	UNCORE_EVENT_CONSTRAINT(0x1d, 0xc),
> >  	UNCORE_EVENT_CONSTRAINT(0x1e, 0xc),
> > -	EVENT_CONSTRAINT_OVERLAP(0x1f, 0xe, 0xff),
> > +	UNCORE_EVENT_CONSTRAINT(0x1f, 0xc); /* should be 0x0e but that
> gives
> > +scheduling pain */

I think the crash is caused by the overlap bit.
Why not just revert the previous patch?

If overlap bit is removed, the perf_sched_save_state will never be touched.
Why we have to reduce a counter?

Thanks,
Kan

> >  	UNCORE_EVENT_CONSTRAINT(0x21, 0x3),
> >  	UNCORE_EVENT_CONSTRAINT(0x23, 0x3),
> >  	UNCORE_EVENT_CONSTRAINT(0x31, 0x3),
> >