linux-kernel - Re: [PATCH] perf powerpc: Don't call perf_event

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Message-ID: <20161006072415.GF3568@worktop.programming.kicks-ass.net>
Date:   Thu, 6 Oct 2016 09:24:15 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Jiri Olsa <jolsa@...hat.com>
Cc:     Michael Ellerman <mpe@...erman.id.au>,
        Michael Neuling <mikey@...ling.org>,
        Paul Mackerras <paulus@...ba.org>,
        Jiri Olsa <jolsa@...nel.org>,
        lkml <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...nel.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jan Stancek <jstancek@...hat.com>
Subject: Re: [PATCH] perf powerpc: Don't call perf_event_disable from atomic
 context

On Wed, Oct 05, 2016 at 09:53:38PM +0200, Jiri Olsa wrote:
> On Wed, Oct 05, 2016 at 10:09:21AM +0200, Jiri Olsa wrote:
> > On Tue, Oct 04, 2016 at 03:29:33PM +1100, Michael Ellerman wrote:
> > 
> > SNIP
> > 
> > > Which is where we cope with the possibility that we couldn't emulate the
> > > instruction that hit the breakpoint. Seems that is not an issue on x86,
> > > or it's handled elsewhere?
> > > 
> > > We should fix emulate_step() if it failed to emulate something it
> > > should have, but there will always be the possibility that it fails.
> > > 
> > > Instead of calling perf_event_disable() we could just add a flag to
> > > arch_hw_breakpoint that says we hit an error on the event, and block
> > > reinstalling it in arch_install_hw_breakpoint().
> > 
> > ok, might be easier.. I'll check on that
> 
> so staring on that I think disabling is the right way here.. 
> 
> we need the event to be unscheduled and not scheduled back
> again, I don't see better way at the moment

OK, can you resend the patch with updated Changelog that explains these
things?