Re: [PATCH v3 00/12] tracing: Add support for in-kernel dynamic event API

[Tom Zanussi]

Hi Masami,

On Mon, 2020-01-27 at 22:48 +0900, Masami Hiramatsu wrote:
> Hi Tom,
> 
> On Fri, 24 Jan 2020 16:56:11 -0600
> Tom Zanussi <zanussi@xxxxxxxxxx> wrote:
> 
> > Hi,
> > 
> > This is v3 of 'tracing: Add support for in-kernel dynamic event
> > API',
> > incorporating changes based on suggestions from Masami and Steven.
> > 
> >   - Rebased to trace/for-next
> > 
> >   - Regularized the entire API to use synth_event_*,
> > kprobe_event_*,
> >     dynevent_*, and added some new macros and functions to make
> > things
> >     more consistent
> > 
> >   - Introduced trace_array_find_get() and used it in
> >     trace_array_get_file() as suggested
> >   
> >   - Removed exports from dynevent_cmd functions that didn't need to
> > be
> >     exported
> > 
> >   - Switched the param order of __kprobe_event_gen_cmd_start() to
> > fix
> >     a problem found building with clang.  Apparently varargs and
> >     implicit promotion of types like bool don't mix.  Thanks to
> > Nick
> >     Desaulniers for pointing that out.
> > 
> >   - Updated the documentation for all of the above
> > 
> > Text from the v2 posting:
> > 
> > This is v2 of the previous 'tracing: Add support for in-kernel
> > synthetic event API', and is largely a rewrite based on suggestions
> > from Masami to expand the scope to include other types of dynamic
> > events such as kprobe events, in addition to the original sythetic
> > event focus.
> 
> Yeah, v3 basically looks good to me now :)
> Please see my comment on [4/12]. Others are good. You can put my
> Acked-by to those patches. 
> 
> Acked-by: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
> except for [04/12].
> 
> Thank you!
> 

OK, I'll add your acks for those.

Thanks for all your comments!

Tom

> > 
> > The functionality of the original API remains available, though
> > it's
> > in a slightly different form due to the use of the new dynevent_cmd
> > API it's now based on.  The dynevent_cmd API provides a common
> > dynamic
> > event command generation capability that both the synthetic event
> > API
> > and the kprobe event API are now based on, and there are now test
> > modules demonstrating both the synthetic event and kprobes APIs.
> > 
> > A couple of the patches are snippets from Masami's 'tracing:
> > bootconfig: Boot-time tracing and Extra boot config' series, and
> > the
> > patch implementing the dynevent_cmd API includes some of the
> > spnprintf() generating code from that patchset.
> > 
> > Because I used Masami's gen_*_cmd() naming suggestion for
> > generating
> > the commands, the previous patchset's generate_*() functions were
> > renamed to trace_*() to avoid confusion, and probably is better
> > naming
> > anyway.
> > 
> > An overview of the user-visible changes in comparison to v1:
> > 
> >   - create_synth_event() using an array of synth_desc_fields
> > remains
> >     unchanged and works the same way as previously
> > 
> >   - gen_synth_cmd() takes a variable-length number of args which
> >     represent 'type field;' pairs.  Using this with no field args
> >     basically replaces the previous 'create_empty_synth_event()'
> > 
> >   - The 'add_synth_field()' and 'add_synth_fields()' function from
> > v1
> >     are essentially the same except that they now take a
> > dynevent_cmd
> >     instead of a synth_event pointer
> > 
> >   - The finalize_synth_event() from v1 is replaced by
> >     create_dynevent() in the new version.
> >   
> >   - The new v2 API includes some additional functions to initialize
> >     the dynevent_cmd - synth_dynevent_cmd() is used to do
> > that.  While
> >     it's an extra step, it makes it easier to do error handling.
> > 
> >   - There's a new trace_synth_event() function that traces a
> > synthetic
> >     event using a variable-arg list of values.
> > 
> >   - The original generate_synth_event() using an array of values is
> >     now called trace_synth_event_array().
> > 
> >   - For piecewise event tracing, the original
> >     generate_synth_event_start() and generate_synth_event_end()
> > have
> >     now been renamed to trace_synth_event_end().
> > 
> >   - add_next_synth_val() and add_synth_val() remain the same.
> > 
> >   - A similar API and test module demonstrating the API has been
> > added
> >     for kprobe events
> > 
> >   - Both the synthetic events and kprobe events API is based on the
> >     dynevent_cmd API, newly added
> > 
> >   - The Documentation for all of the above has been updated
> > 
> > Text from the orginal v1 posting:
> > 
> > I've recently had several requests and suggestions from users to
> > add
> > support for the creation and generation of synthetic events from
> > kernel code such as modules, and not just from the available
> > command
> > line commands.
> > 
> > This patchset adds support for that.  The first three patches add
> > some
> > minor preliminary setup, followed by the two main patches that add
> > the
> > ability to create and generate synthetic events from the
> > kernel.  The
> > next patch adds a test module that demonstrates actual use of the
> > API
> > and verifies that it works as intended, followed by Documentation.
> > 
> > Special thanks to Artem Bityutskiy, who worked with me over several
> > iterations of the API, and who had many great suggestions on the
> > details of the interface, and pointed out several problems with the
> > code itself.
> > 
> > The following changes since commit
> > 659ded30272d67a04b3692f0bfa12263be20d790:
> > 
> >   trace/kprobe: Remove unused MAX_KPROBE_CMDLINE_SIZE (2020-01-22
> > 07:07:38 -0500)
> > 
> > are available in the git repository at:
> > 
> >   git://git.kernel.org/pub/scm/linux/kernel/git/zanussi/linux-
> > trace.git ftrace/synth-event-gen-v3
> > 
> > Tom Zanussi (12):
> >   tracing: Add trace_array_find/_get() to find instance trace
> > arrays
> >   tracing: Add trace_get/put_event_file()
> >   tracing: Add synth_event_delete()
> >   tracing: Add dynamic event command creation interface
> >   tracing: Add synthetic event command generation functions
> >   tracing: Change trace_boot to use synth_event interface
> >   tracing: Add synth_event_trace() and related functions
> >   tracing: Add synth event generation test module
> >   tracing: Add kprobe event command generation functions
> >   tracing: Change trace_boot to use kprobe_event interface
> >   tracing: Add kprobe event command generation test module
> >   tracing: Documentation for in-kernel synthetic event API
> > 
> >  Documentation/trace/events.rst       | 515 ++++++++++++++++++++
> >  include/linux/trace_events.h         | 124 +++++
> >  kernel/trace/Kconfig                 |  25 +
> >  kernel/trace/Makefile                |   2 +
> >  kernel/trace/kprobe_event_gen_test.c | 225 +++++++++
> >  kernel/trace/synth_event_gen_test.c  | 523 ++++++++++++++++++++
> >  kernel/trace/trace.c                 |  43 +-
> >  kernel/trace/trace.h                 |  36 ++
> >  kernel/trace/trace_boot.c            |  66 ++-
> >  kernel/trace/trace_events.c          | 325 +++++++++++++
> >  kernel/trace/trace_events_hist.c     | 896
> > ++++++++++++++++++++++++++++++++++-
> >  kernel/trace/trace_kprobe.c          | 160 ++++++-
> >  12 files changed, 2868 insertions(+), 72 deletions(-)
> >  create mode 100644 kernel/trace/kprobe_event_gen_test.c
> >  create mode 100644 kernel/trace/synth_event_gen_test.c
> > 
> > -- 
> > 2.14.1
> > 
> 
>