linux-kernel - Re: [PATCH 0/2] perf/hw_breakpoint: Fix breakpoint overcommit issue

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Message-ID: <20190716134219.GB4000@lenoir>
Date:   Tue, 16 Jul 2019 15:42:20 +0200
From:   Frederic Weisbecker <frederic@...nel.org>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Borislav Petkov <bp@...e.de>,
        syzbot+370a6b0f11867bf13515@...kaller.appspotmail.com,
        Jiri Olsa <jolsa@...hat.com>, Ingo Molnar <mingo@...nel.org>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Mark Rutland <mark.rutland@....com>
Subject: Re: [PATCH 0/2] perf/hw_breakpoint: Fix breakpoint overcommit issue

On Mon, Jul 15, 2019 at 02:47:37PM +0200, Peter Zijlstra wrote:
> On Thu, Jul 11, 2019 at 12:53:05PM +0200, Peter Zijlstra wrote:
> > > I wish we could use event->ctx->task instead but on pmu::init() there
> > > is no ctx yet (we could pass the task in parameter though) 
> > 
> > Right, that should be fairly easy.
> > 
> > > and on event->destroy() it's TASK_TOMBSTONE and retrieving the task at
> > > that time would be non trivial.
> > 
> > Well, right, we can maybe make TOMBSTONE be the LSB instead of the whole
> > word, then we can recover the task pointer... *yuck* though.
> 
> Something like the attached, completely untested patches.
> 
> I didn't do the hw_breakpoint bit, because I got lost in that, but this
> basically provides what you asked for I think.
> 

Thanks they look good! I can take them and work on top if you like.