From: "Joel Fernandes (Google)" <[email protected]>
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
From: Paul McKenney <[email protected]>
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) <[email protected]>
Signed-off-by: Paul McKenney <[email protected]>
Signed-off-by: Joel Fernandes (Google) <[email protected]>
---
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