Messages in this thread | | | Subject | Re: [PATCH v3 0/7] perf: Add ioctl for PMU driver configuration | From | Suzuki K Poulose <> | Date | Mon, 20 Aug 2018 11:03:03 +0100 |
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On 08/16/2018 08:28 PM, Mathieu Poirier wrote: > On Wed, 15 Aug 2018 at 09:28, Kim Phillips <kim.phillips@arm.com> wrote: >> >> On Wed, 15 Aug 2018 10:39:13 +0100 >> Will Deacon <will.deacon@arm.com> wrote: >> >>> On Tue, Aug 14, 2018 at 01:42:27PM -0600, Mathieu Poirier wrote: >>>> On Tue, 14 Aug 2018 at 11:09, Kim Phillips <kim.phillips@arm.com> wrote: >>>>> The other thing that's going on here is that I'm becoming numb to the >>>>> loathsome "failed to mmap with 12 (Cannot allocate memory)" being >>>>> returned no matter what the error is/was. E.g., an error that would >>>>> indicate a sense of non-implementation would be much better >>>>> appreciated than presumably what the above is doing, i.e., returning >>>>> -ENOMEM. That, backed up with specific details in the form of human >>>>> readable text in dmesg would be *most* welcome. >>>> >>>> As part of the refactoring of the code to support CPU-wide scenarios I >>>> intend to emit better diagnostic messages from the driver. Modifying >>>> rb_alloc_aux() to propagate the error message generated by the >>>> architecture specific PMUs doesn't look hard either and I _may_ get to >>>> it as part of this work. >>> >>> For the record, I will continue to oppose PMU drivers that dump diagnostics >>> about user-controlled input into dmesg, but the coresight drivers are yours >>> so it's up to you and I won't get in the way! >> >> That sounds technically self-contradicting to me. Why shouldn't >> coresight share the same policies as those used for PMU drivers? Or >> why not allow the individual vendor PMU driver authors control the >> level of user-friendliness of their own drivers? >> >> That being said, Matheiu, would you accept patches that make coresight >> more verbose in dmesg? > > It depends on the issue you're hoping to address. I'd rather see the > root cause of the problem fixed than adding temporary code. Suzuki > added the ETR perf API and I'm currently working on CPU-wide > scenarios. From there and with regards to what can happen in > setup_aux(), we should have things covered.
I think the main issue is the lack of error code propagation from setup_aux() back to the perf_aux_output_handle_begin(), which always return -ENOMEM. If we fix that, we could get better idea of whats wrong.
If someone is planning to add verbose messages, they may do so by adding dev_dbg() / pr_debug(), which can be turned on as and when needed.
Suzuki
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