linux-kernel - Re: [PATCH 2/2] perf/hw_breakpoint: Modify breakpoint even if the new attr has disabled set

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Date:   Mon, 6 Aug 2018 15:46:58 +0200
From:   Oleg Nesterov <oleg@...hat.com>
To:     Jiri Olsa <jolsa@...hat.com>
Cc:     Jiri Olsa <jolsa@...nel.org>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Milind Chabbi <chabbi.milind@...il.com>,
        lkml <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        David Ahern <dsahern@...il.com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Peter Zijlstra <a.p.zijlstra@...llo.nl>,
        Frederic Weisbecker <frederic@...nel.org>
Subject: Re: [PATCH 2/2] perf/hw_breakpoint: Modify breakpoint even if the
 new attr has disabled set

On 08/06, Jiri Olsa wrote:
>
> > Afaics you do not need to clear attr.disabled, modify_user_hw_breakpoint_check()
> > updates it if err = 0. So I think
> >
> > 	if (!bp->attr.disabled)
> > 		perf_event_enable(bp);
> >
> > will look a bit better.
> >
> >
> > But, with or without this fix, shouldn't we set .disabled = 1 if modify_() fails?
> > IIUC this doesn't matter, bp->attr.disabled is not really used anyway, but looks a
> > bit confusing.
> >
>
> yea, I was looking on that, but as u said it makes no difference
> and I wanted to keep the patch as simple as possible ;-)

OK. So both patches look good to me.

Acked-by: Oleg Nesterov <oleg@...hat.com>