linux-kernel - Re: [PATCH] perf/x86: Fix overlap counter scheduling bug

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Date:   Tue, 8 Nov 2016 07:09:49 -0800
From:   Andi Kleen <andi@...stfloor.org>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Jiri Olsa <jolsa@...nel.org>, Vince Weaver <vince@...ter.net>,
        Robert Richter <rric@...nel.org>,
        lkml <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...nel.org>,
        Andi Kleen <andi@...stfloor.org>, kan.liang@...el.com
Subject: Re: [PATCH] perf/x86: Fix overlap counter scheduling bug

Adding Kan who actually maintains the uncore drivers these days.

> Which is two distinct groups, only one of which has overlap. And the one
> with overlap only has 2 overlapping masks, giving a max reties of 1.

Looks reasonable to limit the mask.

Are we sure this problem isn't in the other 0xc masks too ?

-Andi

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