linux-kernel - [PATCH v12 0/3] tracing: Centralize preemptirq tracepoints and unify their usage

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Date:   Mon, 30 Jul 2018 15:24:20 -0700
From:   Joel Fernandes <joel@...lfernandes.org>
To:     linux-kernel@...r.kernel.org
Cc:     kernel-team@...roid.com,
        "Joel Fernandes (Google)" <joel@...lfernandes.org>,
        Boqun Feng <boqun.feng@...il.com>,
        Byungchul Park <byungchul.park@....com>,
        Ingo Molnar <mingo@...hat.com>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Paul McKenney <paulmck@...ux.vnet.ibm.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Thomas Glexiner <tglx@...utronix.de>,
        Tom Zanussi <tom.zanussi@...ux.intel.com>
Subject: [PATCH v12 0/3] tracing: Centralize preemptirq tracepoints and unify their usage

From: "Joel Fernandes (Google)" <joel@...lfernandes.org>

This series contains the last 2 patches with minor changes suggested by Peter
and Steven, and an additional clean up of get_lock_stats as suggested by Peter.

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 not possible 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/pull/1801/

v11->v12:
- minor corrections to changelog 
- Added PeterZ's Acks
- Squashed in fix for get_lock_stats

v10->v11:
- Dropped extra unneeded else statement since
  rcu_read_lock_sched_notrace is same as prempt_disable_notrace (PeterZ)

v9->v10:
- Dropped first 3 and last 2 patches that were applied previously
- Folded SPDK license into the main patch introducing trace_preemptirq.c (Steve)
- Dropped lockdep_recursing & use simplify get_cpu_var instead (PeterZ)
- Simplify __DO_TRACE and use rcu_dereference_raw for both RCU and SRCU (PeterZ)

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.

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) (3):
  lockdep: use this_cpu_ptr instead of get_cpu_var stats
  tracepoint: Make rcuidle tracepoint callers use SRCU
  tracing: Centralize preemptirq tracepoints and unify their usage

 include/linux/ftrace.h            |  11 +-
 include/linux/irqflags.h          |  11 +-
 include/linux/lockdep.h           |   8 +-
 include/linux/preempt.h           |   2 +-
 include/linux/tracepoint.h        |  41 ++++--
 include/trace/events/preemptirq.h |  23 +--
 init/main.c                       |   5 +-
 kernel/locking/lockdep.c          |  45 ++----
 kernel/sched/core.c               |   2 +-
 kernel/trace/Kconfig              |  22 ++-
 kernel/trace/Makefile             |   2 +-
 kernel/trace/trace_irqsoff.c      | 231 ++++++++----------------------
 kernel/trace/trace_preemptirq.c   |  72 ++++++++++
 kernel/tracepoint.c               |  16 ++-
 14 files changed, 244 insertions(+), 247 deletions(-)
 create mode 100644 kernel/trace/trace_preemptirq.c

-- 
2.18.0.345.g5c9ce644c3-goog