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

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Message-ID: <20180806142149.GA16446@krava>
Date:   Mon, 6 Aug 2018 16:21:49 +0200
From:   Jiri Olsa <jolsa@...hat.com>
To:     Oleg Nesterov <oleg@...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 Mon, Aug 06, 2018 at 03:49:47PM +0200, Oleg Nesterov wrote:
> On 08/06, Jiri Olsa wrote:
> >
> > On Mon, Aug 06, 2018 at 03:07:31PM +0200, Oleg Nesterov wrote:
> > > On 08/06, Oleg Nesterov wrote:
> > > >
> > > > 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.
> > >
> > > I am looking at another caller perf_event_modify_breakpoint(). It too doesn't set
> > > attr.disabled = 1 on failure, it does _perf_event_enable() instead so attr.disabled
> > > should be correct.
> > >
> > > But this looks wrong. If modify_user_hw_breakpoint_check() paths fails after
> > > arch_validate_hwbkpt_settings() was called, then we can not simply restore
> >
> > hum, arch_validate_hwbkpt_settings was removed recently.. r u checking the last sources?
> 
> I do not see this change in Linus's tree...
> 
> 
> Nevermind, if this was already changed/fixed somewhere, please forget.

should be in tip tree, all around this commit:
  cffbb3bd444b perf/hw_breakpoint: Remove default hw_breakpoint_arch_parse()

jirka