On Mon, 20 Aug 2018 11:03:03 +0100 Suzuki K Poulose <suzuki.poulose@xxxxxxx> wrote: > On 08/16/2018 08:28 PM, Mathieu Poirier wrote: > > On Wed, 15 Aug 2018 at 09:28, Kim Phillips <kim.phillips@xxxxxxx> wrote: > >> > >> On Wed, 15 Aug 2018 10:39:13 +0100 > >> Will Deacon <will.deacon@xxxxxxx> 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@xxxxxxx> 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. Why get a better idea when we can get the exact details? > 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. I disagree: that just adds another usage and kernel configuration obstacle. Why not use pr_err straight up? Kim
