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

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

[Joel Fernandes]

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

[PATCH v9 1/7] srcu: Add notrace variants of srcu_read_{lock,unlock}

[Joel Fernandes]

From: Paul McKenney <paulmck@linux.vnet.ibm.com>

This is needed for a future tracepoint patch that uses srcu, and to make
sure it doesn't call into lockdep.

tracepoint code already calls notrace variants for rcu_read_lock_sched
so this patch does the same for srcu which will be used in a later
patch. Keeps it consistent with rcu-sched.

[Joel: Added commit message]
Reviewed-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: Paul McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
---
 include/linux/srcu.h | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/include/linux/srcu.h b/include/linux/srcu.h
index 91494d7e8e41..3e72a291c401 100644
--- a/include/linux/srcu.h
+++ b/include/linux/srcu.h
@@ -195,6 +195,16 @@ static inline int srcu_read_lock(struct srcu_struct *sp) __acquires(sp)
 	return retval;
 }
 
+/* Used by tracing, cannot be traced and cannot invoke lockdep. */
+static inline notrace int
+srcu_read_lock_notrace(struct srcu_struct *sp) __acquires(sp)
+{
+	int retval;
+
+	retval = __srcu_read_lock(sp);
+	return retval;
+}
+
 /**
  * srcu_read_unlock - unregister a old reader from an SRCU-protected structure.
  * @sp: srcu_struct in which to unregister the old reader.
@@ -209,6 +219,13 @@ static inline void srcu_read_unlock(struct srcu_struct *sp, int idx)
 	__srcu_read_unlock(sp, idx);
 }
 
+/* Used by tracing, cannot be traced and cannot call lockdep. */
+static inline notrace void
+srcu_read_unlock_notrace(struct srcu_struct *sp, int idx) __releases(sp)
+{
+	__srcu_read_unlock(sp, idx);
+}
+
 /**
  * smp_mb__after_srcu_read_unlock - ensure full ordering after srcu_read_unlock
  *
-- 
2.18.0.rc2.346.g013aa6912e-goog

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

[Steven Rostedt]

On Tue, 3 Jul 2018 07:15:37 -0700
Joel Fernandes <joel@joelfernandes.org> wrote:

> 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?
> 

I'm currently chasing down some fires, but I'll try to get to it this
week.

Thanks for the patience ;-)

-- Steve

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

[Joel Fernandes]

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
> 
> 

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

[Joel Fernandes]

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

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

[Joel Fernandes]

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

This is a posting of v9 preempt/irq tracepoint clean up series rebased
onto v4.18-rc1. No changes in the series, just a rebase + repost.
Maintainers, 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. I'm hoping for your consideration of
this series for the kernel. I am also eager for this so that our users
will find it easier to use tools depending on existing preempt
tracepoints since it simplifies the configuration for them.

All patches now have a Reviewed-by tag except for the kselftest script (7/7).
Peter, Ingo, Steve, others, your feedback and Acks are welcomed.

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 [2]. 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://lkml.org/lkml/2018/6/7/1135
[2] https://github.com/iovisor/bcc/pull/1801/

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) (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       |  74 +++++
 20 files changed, 454 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