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

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Date:	Tue, 25 Aug 2015 10:22:28 +0200
From:	Ingo Molnar <mingo@...nel.org>
To:	Alexander Shishkin <alexander.shishkin@...ux.intel.com>
Cc:	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Ingo Molnar <mingo@...hat.com>, linux-kernel@...r.kernel.org,
	adrian.hunter@...el.com,
	Arnaldo Carvalho de Melo <acme@...radead.org>,
	Vince Weaver <vince@...ter.net>,
	Stephane Eranian <eranian@...gle.com>,
	Johannes Berg <johannes@...solutions.net>
Subject: Re: [PATCH v2 0/6] perf: Introduce extended syscall error reporting


* Alexander Shishkin <alexander.shishkin@...ux.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
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