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