Re: [PATCH v9 0/7] Centralize and unify usage of preempt/irq tracepoints

[Joel Fernandes <joel@joelfernandes.org>]

On Thu, Jun 28, 2018 at 11:21:42AM -0700, Joel Fernandes wrote:
> From: "Joel Fernandes (Google)" <joel@joelfernandes.org>
> 
> This is a posting of v9 preempt/irq tracepoint clean up series rebased
> onto v4.18-rc2. No changes in the series, just a rebase + repost.
> 
> All patches have a Reviewed-by tags now from reviewers. This series has
> been well tested and is a simplification/refactoring of existing code,
> along with giving a speed-up for tracepoints using the rcu-idle API.
> With this our users will find it easier to use tools depending on
> existing preempt tracepoints since it simplifies the configuration for
> them.

Steve, all patches of this tracing series have been reviewed and/or acked and
there haven't been additional changes for a couple of reposts. Are you Ok
with it?

Thanks,

-Joel


> Future enhancements/fixes I am developing for preempt-off tracer will
> depend on these patches, so I suggest prioritizing these well reviewed
> and tested patches for that reason as well.
> 
> Introduction to the series:
> The preempt/irq tracepoints exist but not everything in the kernel is using it
> whenever they need to be notified that a preempt disable/enable or an irq
> disable/enable has occurred.  This makes things not work simultaneously (for
> example, only either lockdep or irqsoff trace-events can be used at a time).
> 
> This is particularly painful to deal with, since turning on lockdep breaks
> tracers that install probes on IRQ events, such as the BCC atomic critical
> section tracer [1]. This constraint also makes it impossible to use synthetic
> events to trace irqsoff sections with lockdep simulataneously turned on.
> 
> This series solves that, and also results in a nice clean up of relevant parts
> of the kernel. Several ifdefs are simpler, and the design is more unified and
> better. Also as a result of this, we also speeded performance all rcuidle
> tracepoints since their handling is simpler.
> 
> [1] https://github.com/iovisor/bcc/blob/master/tools/criticalstat_example.txt
> 
> v8->v9:
> - Small style changes to tracepoint code (Mathieu)
> - Minor style fix to use PTR_ERR_OR_ZERO (0-day bot)
> - Minor fix to test_atomic_sections to use unsigned long.
> - Added Namhyung's, Mathieu's Reviewed-by to some patches.
> - Added Acks from Matsami
> 
> v7->v8:
> - Refactored irqsoff tracer probe defines (Namhyung)
> 
> v6->v7:
> - Added a module to simulate an atomic section, a kselftest to load and
>   and trigger it which verifies the preempt-tracer and this series.
> 
> - Fixed a new warning after I rebased in early boot, this is because
> early_boot_irqs_disabled was set too early, I moved it after the lockdep
> initialization.
> 
> - added back the softirq fix since it appears it wasn't picked up.
> 
> - Ran Ingo's locking API selftest suite which are passing with this
>   series.
> 
> - Mathieu suggested ifdef'ing the tracepoint_synchronize_unregister
>   function incase tracepoints aren't enabled, did that.
> 
> 
> Joel Fernandes (Google) (6):
>   srcu: Add notrace variant of srcu_dereference
>   trace/irqsoff: Split reset into separate functions
>   tracepoint: Make rcuidle tracepoint callers use SRCU
>   tracing: Centralize preemptirq tracepoints and unify their usage
>   lib: Add module to simulate atomic sections for testing preemptoff
>     tracers
>   kselftests: Add tests for the preemptoff and irqsoff tracers
> 
> Paul McKenney (1):
>   srcu: Add notrace variants of srcu_read_{lock,unlock}
> 
>  include/linux/ftrace.h                        |  11 +-
>  include/linux/irqflags.h                      |  11 +-
>  include/linux/lockdep.h                       |   8 +-
>  include/linux/preempt.h                       |   2 +-
>  include/linux/srcu.h                          |  22 ++
>  include/linux/tracepoint.h                    |  49 +++-
>  include/trace/events/preemptirq.h             |  23 +-
>  init/main.c                                   |   5 +-
>  kernel/locking/lockdep.c                      |  35 +--
>  kernel/sched/core.c                           |   2 +-
>  kernel/trace/Kconfig                          |  22 +-
>  kernel/trace/Makefile                         |   2 +-
>  kernel/trace/trace_irqsoff.c                  | 253 ++++++------------
>  kernel/trace/trace_preemptirq.c               |  71 +++++
>  kernel/tracepoint.c                           |  16 +-
>  lib/Kconfig.debug                             |   8 +
>  lib/Makefile                                  |   1 +
>  lib/test_atomic_sections.c                    |  77 ++++++
>  tools/testing/selftests/ftrace/config         |   3 +
>  .../test.d/preemptirq/irqsoff_tracer.tc       |  73 +++++
>  20 files changed, 453 insertions(+), 241 deletions(-)
>  create mode 100644 kernel/trace/trace_preemptirq.c
>  create mode 100644 lib/test_atomic_sections.c
>  create mode 100644 tools/testing/selftests/ftrace/test.d/preemptirq/irqsoff_tracer.tc
> 
> -- 
> 2.18.0.rc2.346.g013aa6912e-goog
> 
>