Re: [PATCH v2 0/6] perf: Introduce extended syscall error reporting

Ingo Molnar
2015-08-25T08:22:42Z

* Alexander Shishkin <alexander.shishkin@linux.intel.com> wrote:

> Hi Peter and Ingo and everybody,
>
> Here's an update of my extended error reporting patchset, addressing
> review comments and adding a few more error messages to PT and BTS
> drivers.
>
> Changes since v1:
> * addressed Peter's comments,
> * added perf_err() annotation to intel_pt and intel_bts drivers;
> especially the former is rich in EINVALs in event validation path,
> so it should be immediately useful;
> * changed the error code to EINVAL for the case when perf_err() is
> supplied a non-constart error code;
> * dropped RFC, added sign-offs.
>
> This time around, I employed a linker trick to convert the structures
> containing extended error information into integers, which are then
> made to look just like normal error codes so that IS_ERR_VALUE() and
> friends would still work correctly on them. So no extra pointers in
> the struct perf_event or anywhere else; the extended error codes are
> passed around like normal error codes. They only need to be converted
> in syscalls' topmost return statements. This is done in 1/6.

Nice trick!

> Then, 2/6 illustrates how error sites can be extended to include more
> information such as file names and line numbers [1]. Side note, it can
> be dropped without impact on other patches.
>
> The other patches add perf_err() annotation to a few semi-randomly
> picked places in perf core (3/6), x86 bits (4/6), intel_pt (5/6) and
> intel_bts (6/6).
>
> [1] http://marc.info/?l=linux-kernel&m=141471816115946
>
> Alexander Shishkin (6):
> perf: Introduce extended syscall error reporting
> perf: Add file name and line number to perf extended error reports
> perf: Annotate some of the error codes with perf_err()
> perf/x86: Annotate some of the error codes with perf_err()
> perf/x86/intel/pt: Use extended error reporting in event
> initialization
> perf/x86/intel/bts: Use extended error reporting in event
> initialization
>
> arch/x86/kernel/cpu/perf_event.c | 8 +-
> arch/x86/kernel/cpu/perf_event_intel_bts.c | 4 +-
> arch/x86/kernel/cpu/perf_event_intel_lbr.c | 2 +-
> arch/x86/kernel/cpu/perf_event_intel_pt.c | 29 +++++---
> include/linux/perf_event.h | 82 +++++++++++++++++++++
> include/uapi/linux/perf_event.h | 8 +-
> kernel/events/core.c | 113 +++++++++++++++++++++++++----
> 7 files changed, 215 insertions(+), 31 deletions(-)

Ok, this looks pretty good to me.

Mind adding support on the perf tooling side as well, so that it can be tested and
applied in a single set of patches?

Thanks,

Ingo