linux-kernel - Re: [PATCH 01/12] perf/breakpoint: Split attribute parse and commit

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Date:   Mon, 28 May 2018 21:29:59 +1000
From:   Michael Ellerman <mpe@...erman.id.au>
To:     Frederic Weisbecker <frederic@...nel.org>
Cc:     LKML <linux-kernel@...r.kernel.org>, Jiri Olsa <jolsa@...hat.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Joel Fernandes <joel.opensrc@...il.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Yoshinori Sato <ysato@...rs.sourceforge.jp>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Chris Zankel <chris@...kel.net>,
        Paul Mackerras <paulus@...ba.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Will Deacon <will.deacon@....com>,
        Rich Felker <dalias@...c.org>, Ingo Molnar <mingo@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Andy Lutomirski <luto@...nel.org>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Max Filippov <jcmvbkbc@...il.com>
Subject: Re: [PATCH 01/12] perf/breakpoint: Split attribute parse and commit

Frederic Weisbecker <frederic@...nel.org> writes:

> On Thu, May 24, 2018 at 11:56:01AM +1000, Michael Ellerman wrote:
>> Frederic Weisbecker <frederic@...nel.org> writes:
>> 
>> > diff --git a/kernel/events/hw_breakpoint.c b/kernel/events/hw_breakpoint.c
>> > index 6e28d28..51320c2 100644
>> > --- a/kernel/events/hw_breakpoint.c
>> > +++ b/kernel/events/hw_breakpoint.c
>> > @@ -424,19 +443,22 @@ static int validate_hw_breakpoint(struct perf_event *bp)
>> >  
>> >  int register_perf_hw_breakpoint(struct perf_event *bp)
>> >  {
>> > -	int ret;
>> > +	struct arch_hw_breakpoint hw;
>> > +	int err;
>> >  
>> > -	ret = reserve_bp_slot(bp);
>> > -	if (ret)
>> > -		return ret;
>> > +	err = reserve_bp_slot(bp);
>> > +	if (err)
>> > +		return err;
>> >  
>> > -	ret = validate_hw_breakpoint(bp);
>> > -
>> > -	/* if arch_validate_hwbkpt_settings() fails then release bp slot */
>> > -	if (ret)
>> > +	err = hw_breakpoint_parse(bp, &bp->attr, &hw);
>> 
>> Is there a good reason we pass bp and bp->attr? (I assume so)
>> 
>> That added to the confusion in the existing code I think.
>
> Yes, on breakpoint creation (which is the above function) it's not needed
> but breakpoint modification wants it as we need to pass the attr that are
> to be validated, and those are not yet copied to the breakpoint at this
> stage. This happens in the end of the series.

OK thanks.

cheers