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    Subject[PATCH v9 0/7] Centralize and unify usage of preempt/irq tracepoints
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    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.

    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


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