Messages in this thread |  | | Date | Mon, 10 Oct 2016 14:19:02 +0100 | From | Will Deacon <> | Subject | Re: [PATCH] perf powerpc: Don't call perf_event_disable from atomic context |
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On Tue, Oct 04, 2016 at 09:06:18AM +0200, Peter Zijlstra wrote: > 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 don't do any emulation, so no need for us to call perf_event_disable in the hw_breakpoint "overflow" path. We do play some awful games to fake up a single-step, but I don't think perf core needs to care about it.
Will
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