From: Peter Zijlstra <peterz@infradead.org>
To: Michael Ellerman <mpe@ellerman.id.au>
Cc: Jiri Olsa <jolsa@redhat.com>, Michael Neuling <mikey@neuling.org>,
Paul Mackerras <paulus@samba.org>, Jiri Olsa <jolsa@kernel.org>,
lkml <linux-kernel@vger.kernel.org>,
Ingo Molnar <mingo@kernel.org>,
Alexander Shishkin <alexander.shishkin@linux.intel.com>,
Jan Stancek <jstancek@redhat.com>,
Will Deacon <will.deacon@arm.com>
Subject: Re: [PATCH] perf powerpc: Don't call perf_event_disable from atomic context
Date: Tue, 4 Oct 2016 09:06:18 +0200 [thread overview]
Message-ID: <20161004070618.GL3318@worktop.controleur.wifipass.org> (raw)
In-Reply-To: <87shsc4tzm.fsf@concordia.ellerman.id.au>
On Tue, Oct 04, 2016 at 03:29:33PM +1100, Michael Ellerman wrote:
> Peter Zijlstra <peterz@infradead.org> writes:
> > So it would be good to also explain why PPC needs this in the first
> > place.
>
> Unfortunately I don't really know the code, and the original author is AWOL.
>
> But AFAICS perf_event_disable() is only called here:
>
> if (!stepped) {
> WARN(1, "Unable to handle hardware breakpoint. Breakpoint at "
> "0x%lx will be disabled.", info->address);
> perf_event_disable(bp);
> goto out;
> }
>
> 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?
I don't think x86 ever needs to emulate things on hw breakpoint
(although I could be mistaken), but I would expect ARM to maybe need
so, and I couldn't find a disable there either.
Will?
> 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().
Possible..
next prev parent reply other threads:[~2016-10-04 7:06 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-09-21 13:55 [PATCH] perf powerpc: Don't call perf_event_disable from atomic context Jiri Olsa
2016-09-23 16:37 ` Peter Zijlstra
2016-10-03 13:29 ` Jiri Olsa
2016-10-03 13:47 ` Peter Zijlstra
2016-10-04 4:29 ` Michael Ellerman
2016-10-04 7:06 ` Peter Zijlstra [this message]
2016-10-10 13:19 ` Will Deacon
2016-10-05 8:09 ` Jiri Olsa
2016-10-05 19:53 ` Jiri Olsa
2016-10-06 7:24 ` Peter Zijlstra
2016-10-06 12:33 ` [PATCHv2] " Jiri Olsa
2016-10-24 12:26 ` Peter Zijlstra
2016-10-24 15:49 ` Jiri Olsa
2016-10-25 6:40 ` [lkp] [perf powerpc] 18d1796d0b: [No primary change] kernel test robot
2016-10-25 9:06 ` Peter Zijlstra
2016-10-26 2:09 ` [LKP] " Huang, Ying
2016-10-26 9:48 ` [PATCHv3] perf powerpc: Don't call perf_event_disable from atomic context Jiri Olsa
2016-10-26 15:12 ` Peter Zijlstra
2016-10-26 15:24 ` Jiri Olsa
2016-10-28 10:10 ` [tip:perf/urgent] perf/powerpc: Don't call perf_event_disable() " tip-bot for Jiri Olsa
2016-10-04 4:08 ` [PATCH] perf powerpc: Don't call perf_event_disable " Michael Ellerman
2016-10-05 8:08 ` Jiri Olsa
2016-10-05 8:21 ` Jan Stancek
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