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* [PATCH v7 0/8] Centralize and unify usage of preempt/irq tracepoints
@ 2018-05-24  1:21 ` joelaf
  0 siblings, 0 replies; 33+ messages in thread
From: Joel Fernandes @ 2018-05-24  1:21 UTC (permalink / raw)
  To: linux-kernel
  Cc: kernel-team, Joel Fernandes (Google),
	Boqun Feng, Byungchul Park, Erick Reyes, Ingo Molnar,
	Julia Cartwright, linux-kselftest, Masami Hiramatsu,
	Mathieu Desnoyers, Namhyung Kim, Paul McKenney, Peter Zijlstra,
	Shuah Khan, Steven Rostedt, Thomas Glexiner, Todd Kjos,
	Tom Zanussi

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

This is the next revision of preempt/irq tracepoint centralization and
unified usage across the kernel.
The preempt/irq tracepoints exist but not everything in the kernel is
using it. This makes things not work simultaneously (for ex, only either
lockdep or irqsoff events can be used at a time). This series is an attempt to
solve that, and also results in a nice clean up of kernel in general.
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.

Few changes since v6:
- Added a module to simulate an atomic section, a kselftest to load and
  and trigger it which verifies the preempt-tracer and this series.

- there is 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) (7):
  softirq: reorder trace_softirqs_on to prevent lockdep splat
  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                    |  48 +++-
 include/trace/events/preemptirq.h             |  23 +-
 init/main.c                                   |   5 +-
 kernel/locking/lockdep.c                      |  35 ++-
 kernel/sched/core.c                           |   2 +-
 kernel/softirq.c                              |   6 +-
 kernel/trace/Kconfig                          |  22 +-
 kernel/trace/Makefile                         |   2 +-
 kernel/trace/trace_irqsoff.c                  | 235 ++++++------------
 kernel/trace/trace_preemptirq.c               |  71 ++++++
 kernel/tracepoint.c                           |  15 +-
 lib/Kconfig.debug                             |   8 +
 lib/Makefile                                  |   1 +
 lib/test_atomic_sections.c                    |  79 ++++++
 tools/testing/selftests/ftrace/config         |   3 +
 .../test.d/preemptirq/irqsoff_tracer.tc       |  74 ++++++
 21 files changed, 454 insertions(+), 229 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

-- 
2.17.0.441.gb46fe60e1d-goog

^ permalink raw reply	[flat|nested] 33+ messages in thread

* [PATCH v7 0/8] Centralize and unify usage of preempt/irq tracepoints
@ 2018-05-24  1:21 ` joelaf
  0 siblings, 0 replies; 33+ messages in thread
From: joelaf @ 2018-05-24  1:21 UTC (permalink / raw)


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

This is the next revision of preempt/irq tracepoint centralization and
unified usage across the kernel.
The preempt/irq tracepoints exist but not everything in the kernel is
using it. This makes things not work simultaneously (for ex, only either
lockdep or irqsoff events can be used at a time). This series is an attempt to
solve that, and also results in a nice clean up of kernel in general.
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.

Few changes since v6:
- Added a module to simulate an atomic section, a kselftest to load and
  and trigger it which verifies the preempt-tracer and this series.

- there is 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) (7):
  softirq: reorder trace_softirqs_on to prevent lockdep splat
  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                    |  48 +++-
 include/trace/events/preemptirq.h             |  23 +-
 init/main.c                                   |   5 +-
 kernel/locking/lockdep.c                      |  35 ++-
 kernel/sched/core.c                           |   2 +-
 kernel/softirq.c                              |   6 +-
 kernel/trace/Kconfig                          |  22 +-
 kernel/trace/Makefile                         |   2 +-
 kernel/trace/trace_irqsoff.c                  | 235 ++++++------------
 kernel/trace/trace_preemptirq.c               |  71 ++++++
 kernel/tracepoint.c                           |  15 +-
 lib/Kconfig.debug                             |   8 +
 lib/Makefile                                  |   1 +
 lib/test_atomic_sections.c                    |  79 ++++++
 tools/testing/selftests/ftrace/config         |   3 +
 .../test.d/preemptirq/irqsoff_tracer.tc       |  74 ++++++
 21 files changed, 454 insertions(+), 229 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

-- 
2.17.0.441.gb46fe60e1d-goog
--
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^ permalink raw reply	[flat|nested] 33+ messages in thread

* [PATCH v7 0/8] Centralize and unify usage of preempt/irq tracepoints
@ 2018-05-24  1:21 ` joelaf
  0 siblings, 0 replies; 33+ messages in thread
From: Joel Fernandes @ 2018-05-24  1:21 UTC (permalink / raw)


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

This is the next revision of preempt/irq tracepoint centralization and
unified usage across the kernel.
The preempt/irq tracepoints exist but not everything in the kernel is
using it. This makes things not work simultaneously (for ex, only either
lockdep or irqsoff events can be used at a time). This series is an attempt to
solve that, and also results in a nice clean up of kernel in general.
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.

Few changes since v6:
- Added a module to simulate an atomic section, a kselftest to load and
  and trigger it which verifies the preempt-tracer and this series.

- there is 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) (7):
  softirq: reorder trace_softirqs_on to prevent lockdep splat
  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                    |  48 +++-
 include/trace/events/preemptirq.h             |  23 +-
 init/main.c                                   |   5 +-
 kernel/locking/lockdep.c                      |  35 ++-
 kernel/sched/core.c                           |   2 +-
 kernel/softirq.c                              |   6 +-
 kernel/trace/Kconfig                          |  22 +-
 kernel/trace/Makefile                         |   2 +-
 kernel/trace/trace_irqsoff.c                  | 235 ++++++------------
 kernel/trace/trace_preemptirq.c               |  71 ++++++
 kernel/tracepoint.c                           |  15 +-
 lib/Kconfig.debug                             |   8 +
 lib/Makefile                                  |   1 +
 lib/test_atomic_sections.c                    |  79 ++++++
 tools/testing/selftests/ftrace/config         |   3 +
 .../test.d/preemptirq/irqsoff_tracer.tc       |  74 ++++++
 21 files changed, 454 insertions(+), 229 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

-- 
2.17.0.441.gb46fe60e1d-goog
--
To unsubscribe from this list: send the line "unsubscribe linux-kselftest" in
the body of a message to majordomo at vger.kernel.org
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^ permalink raw reply	[flat|nested] 33+ messages in thread

* [PATCH v7 1/8] softirq: reorder trace_softirqs_on to prevent lockdep splat
  2018-05-24  1:21 ` joelaf
  (?)
@ 2018-05-24  1:21   ` joelaf
  -1 siblings, 0 replies; 33+ messages in thread
From: Joel Fernandes @ 2018-05-24  1:21 UTC (permalink / raw)
  To: linux-kernel
  Cc: kernel-team, Joel Fernandes (Google),
	stable, Boqun Feng, Byungchul Park, Erick Reyes, Ingo Molnar,
	Julia Cartwright, linux-kselftest, Masami Hiramatsu,
	Mathieu Desnoyers, Namhyung Kim, Paul McKenney, Peter Zijlstra,
	Shuah Khan, Steven Rostedt, Thomas Glexiner, Todd Kjos,
	Tom Zanussi

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

I'm able to reproduce a lockdep splat with config options:
CONFIG_PROVE_LOCKING=y,
CONFIG_DEBUG_LOCK_ALLOC=y and
CONFIG_PREEMPTIRQ_EVENTS=y

$ echo 1 > /d/tracing/events/preemptirq/preempt_enable/enable

[   26.112609] DEBUG_LOCKS_WARN_ON(current->softirqs_enabled)
[   26.112636] WARNING: CPU: 0 PID: 118 at kernel/locking/lockdep.c:3854
[...]
[   26.144229] Call Trace:
[   26.144926]  <IRQ>
[   26.145506]  lock_acquire+0x55/0x1b0
[   26.146499]  ? __do_softirq+0x46f/0x4d9
[   26.147571]  ? __do_softirq+0x46f/0x4d9
[   26.148646]  trace_preempt_on+0x8f/0x240
[   26.149744]  ? trace_preempt_on+0x4d/0x240
[   26.150862]  ? __do_softirq+0x46f/0x4d9
[   26.151930]  preempt_count_sub+0x18a/0x1a0
[   26.152985]  __do_softirq+0x46f/0x4d9
[   26.153937]  irq_exit+0x68/0xe0
[   26.154755]  smp_apic_timer_interrupt+0x271/0x280
[   26.156056]  apic_timer_interrupt+0xf/0x20
[   26.157105]  </IRQ>

The issue was this:

preempt_count = 1 << SOFTIRQ_SHIFT

	__local_bh_enable(cnt = 1 << SOFTIRQ_SHIFT) {
		if (softirq_count() == (cnt && SOFTIRQ_MASK)) {
			trace_softirqs_on() {
				current->softirqs_enabled = 1;
			}
		}
		preempt_count_sub(cnt) {
			trace_preempt_on() {
				tracepoint() {
					rcu_read_lock_sched() {
						// jumps into lockdep

Where preempt_count still has softirqs disabled, but
current->softirqs_enabled is true, and we get a splat.

Cc: stable@vger.kernel.org
Reviewed-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Fixes: d59158162e032 ("tracing: Add support for preempt and irq enable/disable events")
Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
---
 kernel/softirq.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/kernel/softirq.c b/kernel/softirq.c
index 177de3640c78..8a040bcaa033 100644
--- a/kernel/softirq.c
+++ b/kernel/softirq.c
@@ -139,9 +139,13 @@ static void __local_bh_enable(unsigned int cnt)
 {
 	lockdep_assert_irqs_disabled();
 
+	if (preempt_count() == cnt)
+		trace_preempt_on(CALLER_ADDR0, get_lock_parent_ip());
+
 	if (softirq_count() == (cnt & SOFTIRQ_MASK))
 		trace_softirqs_on(_RET_IP_);
-	preempt_count_sub(cnt);
+
+	__preempt_count_sub(cnt);
 }
 
 /*
-- 
2.17.0.441.gb46fe60e1d-goog

^ permalink raw reply	[flat|nested] 33+ messages in thread

* [PATCH v7 1/8] softirq: reorder trace_softirqs_on to prevent lockdep splat
@ 2018-05-24  1:21   ` joelaf
  0 siblings, 0 replies; 33+ messages in thread
From: joelaf @ 2018-05-24  1:21 UTC (permalink / raw)


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

I'm able to reproduce a lockdep splat with config options:
CONFIG_PROVE_LOCKING=y,
CONFIG_DEBUG_LOCK_ALLOC=y and
CONFIG_PREEMPTIRQ_EVENTS=y

$ echo 1 > /d/tracing/events/preemptirq/preempt_enable/enable

[   26.112609] DEBUG_LOCKS_WARN_ON(current->softirqs_enabled)
[   26.112636] WARNING: CPU: 0 PID: 118 at kernel/locking/lockdep.c:3854
[...]
[   26.144229] Call Trace:
[   26.144926]  <IRQ>
[   26.145506]  lock_acquire+0x55/0x1b0
[   26.146499]  ? __do_softirq+0x46f/0x4d9
[   26.147571]  ? __do_softirq+0x46f/0x4d9
[   26.148646]  trace_preempt_on+0x8f/0x240
[   26.149744]  ? trace_preempt_on+0x4d/0x240
[   26.150862]  ? __do_softirq+0x46f/0x4d9
[   26.151930]  preempt_count_sub+0x18a/0x1a0
[   26.152985]  __do_softirq+0x46f/0x4d9
[   26.153937]  irq_exit+0x68/0xe0
[   26.154755]  smp_apic_timer_interrupt+0x271/0x280
[   26.156056]  apic_timer_interrupt+0xf/0x20
[   26.157105]  </IRQ>

The issue was this:

preempt_count = 1 << SOFTIRQ_SHIFT

	__local_bh_enable(cnt = 1 << SOFTIRQ_SHIFT) {
		if (softirq_count() == (cnt && SOFTIRQ_MASK)) {
			trace_softirqs_on() {
				current->softirqs_enabled = 1;
			}
		}
		preempt_count_sub(cnt) {
			trace_preempt_on() {
				tracepoint() {
					rcu_read_lock_sched() {
						// jumps into lockdep

Where preempt_count still has softirqs disabled, but
current->softirqs_enabled is true, and we get a splat.

Cc: stable at vger.kernel.org
Reviewed-by: Steven Rostedt (VMware) <rostedt at goodmis.org>
Fixes: d59158162e032 ("tracing: Add support for preempt and irq enable/disable events")
Signed-off-by: Joel Fernandes (Google) <joel at joelfernandes.org>
---
 kernel/softirq.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/kernel/softirq.c b/kernel/softirq.c
index 177de3640c78..8a040bcaa033 100644
--- a/kernel/softirq.c
+++ b/kernel/softirq.c
@@ -139,9 +139,13 @@ static void __local_bh_enable(unsigned int cnt)
 {
 	lockdep_assert_irqs_disabled();
 
+	if (preempt_count() == cnt)
+		trace_preempt_on(CALLER_ADDR0, get_lock_parent_ip());
+
 	if (softirq_count() == (cnt & SOFTIRQ_MASK))
 		trace_softirqs_on(_RET_IP_);
-	preempt_count_sub(cnt);
+
+	__preempt_count_sub(cnt);
 }
 
 /*
-- 
2.17.0.441.gb46fe60e1d-goog

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^ permalink raw reply	[flat|nested] 33+ messages in thread

* [PATCH v7 1/8] softirq: reorder trace_softirqs_on to prevent lockdep splat
@ 2018-05-24  1:21   ` joelaf
  0 siblings, 0 replies; 33+ messages in thread
From: Joel Fernandes @ 2018-05-24  1:21 UTC (permalink / raw)


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

I'm able to reproduce a lockdep splat with config options:
CONFIG_PROVE_LOCKING=y,
CONFIG_DEBUG_LOCK_ALLOC=y and
CONFIG_PREEMPTIRQ_EVENTS=y

$ echo 1 > /d/tracing/events/preemptirq/preempt_enable/enable

[   26.112609] DEBUG_LOCKS_WARN_ON(current->softirqs_enabled)
[   26.112636] WARNING: CPU: 0 PID: 118 at kernel/locking/lockdep.c:3854
[...]
[   26.144229] Call Trace:
[   26.144926]  <IRQ>
[   26.145506]  lock_acquire+0x55/0x1b0
[   26.146499]  ? __do_softirq+0x46f/0x4d9
[   26.147571]  ? __do_softirq+0x46f/0x4d9
[   26.148646]  trace_preempt_on+0x8f/0x240
[   26.149744]  ? trace_preempt_on+0x4d/0x240
[   26.150862]  ? __do_softirq+0x46f/0x4d9
[   26.151930]  preempt_count_sub+0x18a/0x1a0
[   26.152985]  __do_softirq+0x46f/0x4d9
[   26.153937]  irq_exit+0x68/0xe0
[   26.154755]  smp_apic_timer_interrupt+0x271/0x280
[   26.156056]  apic_timer_interrupt+0xf/0x20
[   26.157105]  </IRQ>

The issue was this:

preempt_count = 1 << SOFTIRQ_SHIFT

	__local_bh_enable(cnt = 1 << SOFTIRQ_SHIFT) {
		if (softirq_count() == (cnt && SOFTIRQ_MASK)) {
			trace_softirqs_on() {
				current->softirqs_enabled = 1;
			}
		}
		preempt_count_sub(cnt) {
			trace_preempt_on() {
				tracepoint() {
					rcu_read_lock_sched() {
						// jumps into lockdep

Where preempt_count still has softirqs disabled, but
current->softirqs_enabled is true, and we get a splat.

Cc: stable at vger.kernel.org
Reviewed-by: Steven Rostedt (VMware) <rostedt at goodmis.org>
Fixes: d59158162e032 ("tracing: Add support for preempt and irq enable/disable events")
Signed-off-by: Joel Fernandes (Google) <joel at joelfernandes.org>
---
 kernel/softirq.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/kernel/softirq.c b/kernel/softirq.c
index 177de3640c78..8a040bcaa033 100644
--- a/kernel/softirq.c
+++ b/kernel/softirq.c
@@ -139,9 +139,13 @@ static void __local_bh_enable(unsigned int cnt)
 {
 	lockdep_assert_irqs_disabled();
 
+	if (preempt_count() == cnt)
+		trace_preempt_on(CALLER_ADDR0, get_lock_parent_ip());
+
 	if (softirq_count() == (cnt & SOFTIRQ_MASK))
 		trace_softirqs_on(_RET_IP_);
-	preempt_count_sub(cnt);
+
+	__preempt_count_sub(cnt);
 }
 
 /*
-- 
2.17.0.441.gb46fe60e1d-goog

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^ permalink raw reply	[flat|nested] 33+ messages in thread

* [PATCH v7 2/8] srcu: Add notrace variants of srcu_read_{lock,unlock}
  2018-05-24  1:21 ` joelaf
  (?)
@ 2018-05-24  1:21   ` joelaf
  -1 siblings, 0 replies; 33+ messages in thread
From: Joel Fernandes @ 2018-05-24  1:21 UTC (permalink / raw)
  To: linux-kernel
  Cc: kernel-team, Paul McKenney, Joel Fernandes, Boqun Feng,
	Byungchul Park, Erick Reyes, Ingo Molnar, Julia Cartwright,
	linux-kselftest, Masami Hiramatsu, Mathieu Desnoyers,
	Namhyung Kim, Peter Zijlstra, Shuah Khan, Steven Rostedt,
	Thomas Glexiner, Todd Kjos, Tom Zanussi

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 33c1c698df09..2ec618979b20 100644
--- a/include/linux/srcu.h
+++ b/include/linux/srcu.h
@@ -161,6 +161,16 @@ 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.
@@ -175,6 +185,13 @@ 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
  *
-- 
2.17.0.441.gb46fe60e1d-goog

^ permalink raw reply	[flat|nested] 33+ messages in thread

* [PATCH v7 2/8] srcu: Add notrace variants of srcu_read_{lock,unlock}
@ 2018-05-24  1:21   ` joelaf
  0 siblings, 0 replies; 33+ messages in thread
From: joelaf @ 2018-05-24  1:21 UTC (permalink / raw)


From: Paul McKenney <paulmck at 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 at goodmis.org>
Signed-off-by: Paul McKenney <paulmck at linux.vnet.ibm.com>
Signed-off-by: Joel Fernandes (Google) <joel at 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 33c1c698df09..2ec618979b20 100644
--- a/include/linux/srcu.h
+++ b/include/linux/srcu.h
@@ -161,6 +161,16 @@ 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.
@@ -175,6 +185,13 @@ 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
  *
-- 
2.17.0.441.gb46fe60e1d-goog

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^ permalink raw reply	[flat|nested] 33+ messages in thread

* [PATCH v7 2/8] srcu: Add notrace variants of srcu_read_{lock,unlock}
@ 2018-05-24  1:21   ` joelaf
  0 siblings, 0 replies; 33+ messages in thread
From: Joel Fernandes @ 2018-05-24  1:21 UTC (permalink / raw)


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 at goodmis.org>
Signed-off-by: Paul McKenney <paulmck at linux.vnet.ibm.com>
Signed-off-by: Joel Fernandes (Google) <joel at 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 33c1c698df09..2ec618979b20 100644
--- a/include/linux/srcu.h
+++ b/include/linux/srcu.h
@@ -161,6 +161,16 @@ 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.
@@ -175,6 +185,13 @@ 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
  *
-- 
2.17.0.441.gb46fe60e1d-goog

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^ permalink raw reply	[flat|nested] 33+ messages in thread

* [PATCH v7 3/8] srcu: Add notrace variant of srcu_dereference
  2018-05-24  1:21 ` joelaf
  (?)
@ 2018-05-24  1:21   ` joelaf
  -1 siblings, 0 replies; 33+ messages in thread
From: Joel Fernandes @ 2018-05-24  1:21 UTC (permalink / raw)
  To: linux-kernel
  Cc: kernel-team, Joel Fernandes (Google),
	Boqun Feng, Byungchul Park, Erick Reyes, Ingo Molnar,
	Julia Cartwright, linux-kselftest, Masami Hiramatsu,
	Mathieu Desnoyers, Namhyung Kim, Paul McKenney, Peter Zijlstra,
	Shuah Khan, Steven Rostedt, Thomas Glexiner, Todd Kjos,
	Tom Zanussi

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

In the last patch in this series, we are making lockdep register hooks
onto the irq_{disable,enable} tracepoints. These tracepoints use the
_rcuidle tracepoint variant. In this series we switch the _rcuidle
tracepoint callers to use SRCU instead of sched-RCU. Inorder to
dereference the pointer to the probe functions, we could call
srcu_dereference, however this API will call back into lockdep to check
if the lock is held *before* the lockdep probe hooks have a chance to
run and annotate the IRQ enabled/disabled state.

For this reason we need a notrace variant of srcu_dereference since
otherwise we get lockdep splats. This patch adds the needed
srcu_dereference_notrace variant.

Reviewed-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
---
 include/linux/srcu.h | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/include/linux/srcu.h b/include/linux/srcu.h
index 2ec618979b20..a1c4947be877 100644
--- a/include/linux/srcu.h
+++ b/include/linux/srcu.h
@@ -135,6 +135,11 @@ static inline int srcu_read_lock_held(const struct srcu_struct *sp)
  */
 #define srcu_dereference(p, sp) srcu_dereference_check((p), (sp), 0)
 
+/**
+ * srcu_dereference_notrace - no tracing and no lockdep calls from here
+ */
+#define srcu_dereference_notrace(p, sp) srcu_dereference_check((p), (sp), 1)
+
 /**
  * srcu_read_lock - register a new reader for an SRCU-protected structure.
  * @sp: srcu_struct in which to register the new reader.
-- 
2.17.0.441.gb46fe60e1d-goog

^ permalink raw reply	[flat|nested] 33+ messages in thread

* [PATCH v7 3/8] srcu: Add notrace variant of srcu_dereference
@ 2018-05-24  1:21   ` joelaf
  0 siblings, 0 replies; 33+ messages in thread
From: joelaf @ 2018-05-24  1:21 UTC (permalink / raw)


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

In the last patch in this series, we are making lockdep register hooks
onto the irq_{disable,enable} tracepoints. These tracepoints use the
_rcuidle tracepoint variant. In this series we switch the _rcuidle
tracepoint callers to use SRCU instead of sched-RCU. Inorder to
dereference the pointer to the probe functions, we could call
srcu_dereference, however this API will call back into lockdep to check
if the lock is held *before* the lockdep probe hooks have a chance to
run and annotate the IRQ enabled/disabled state.

For this reason we need a notrace variant of srcu_dereference since
otherwise we get lockdep splats. This patch adds the needed
srcu_dereference_notrace variant.

Reviewed-by: Paul E. McKenney <paulmck at linux.vnet.ibm.com>
Signed-off-by: Joel Fernandes (Google) <joel at joelfernandes.org>
---
 include/linux/srcu.h | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/include/linux/srcu.h b/include/linux/srcu.h
index 2ec618979b20..a1c4947be877 100644
--- a/include/linux/srcu.h
+++ b/include/linux/srcu.h
@@ -135,6 +135,11 @@ static inline int srcu_read_lock_held(const struct srcu_struct *sp)
  */
 #define srcu_dereference(p, sp) srcu_dereference_check((p), (sp), 0)
 
+/**
+ * srcu_dereference_notrace - no tracing and no lockdep calls from here
+ */
+#define srcu_dereference_notrace(p, sp) srcu_dereference_check((p), (sp), 1)
+
 /**
  * srcu_read_lock - register a new reader for an SRCU-protected structure.
  * @sp: srcu_struct in which to register the new reader.
-- 
2.17.0.441.gb46fe60e1d-goog

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^ permalink raw reply	[flat|nested] 33+ messages in thread

* [PATCH v7 3/8] srcu: Add notrace variant of srcu_dereference
@ 2018-05-24  1:21   ` joelaf
  0 siblings, 0 replies; 33+ messages in thread
From: Joel Fernandes @ 2018-05-24  1:21 UTC (permalink / raw)


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

In the last patch in this series, we are making lockdep register hooks
onto the irq_{disable,enable} tracepoints. These tracepoints use the
_rcuidle tracepoint variant. In this series we switch the _rcuidle
tracepoint callers to use SRCU instead of sched-RCU. Inorder to
dereference the pointer to the probe functions, we could call
srcu_dereference, however this API will call back into lockdep to check
if the lock is held *before* the lockdep probe hooks have a chance to
run and annotate the IRQ enabled/disabled state.

For this reason we need a notrace variant of srcu_dereference since
otherwise we get lockdep splats. This patch adds the needed
srcu_dereference_notrace variant.

Reviewed-by: Paul E. McKenney <paulmck at linux.vnet.ibm.com>
Signed-off-by: Joel Fernandes (Google) <joel at joelfernandes.org>
---
 include/linux/srcu.h | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/include/linux/srcu.h b/include/linux/srcu.h
index 2ec618979b20..a1c4947be877 100644
--- a/include/linux/srcu.h
+++ b/include/linux/srcu.h
@@ -135,6 +135,11 @@ static inline int srcu_read_lock_held(const struct srcu_struct *sp)
  */
 #define srcu_dereference(p, sp) srcu_dereference_check((p), (sp), 0)
 
+/**
+ * srcu_dereference_notrace - no tracing and no lockdep calls from here
+ */
+#define srcu_dereference_notrace(p, sp) srcu_dereference_check((p), (sp), 1)
+
 /**
  * srcu_read_lock - register a new reader for an SRCU-protected structure.
  * @sp: srcu_struct in which to register the new reader.
-- 
2.17.0.441.gb46fe60e1d-goog

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^ permalink raw reply	[flat|nested] 33+ messages in thread

* [PATCH v7 4/8] trace/irqsoff: Split reset into separate functions
  2018-05-24  1:21 ` joelaf
  (?)
@ 2018-05-24  1:21   ` joelaf
  -1 siblings, 0 replies; 33+ messages in thread
From: Joel Fernandes @ 2018-05-24  1:21 UTC (permalink / raw)
  To: linux-kernel
  Cc: kernel-team, Joel Fernandes (Google),
	Boqun Feng, Byungchul Park, Erick Reyes, Ingo Molnar,
	Julia Cartwright, linux-kselftest, Masami Hiramatsu,
	Mathieu Desnoyers, Namhyung Kim, Paul McKenney, Peter Zijlstra,
	Shuah Khan, Steven Rostedt, Thomas Glexiner, Todd Kjos,
	Tom Zanussi

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

Split reset functions into seperate functions in preparation
of future patches that need to do tracer specific reset.

Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
---
 kernel/trace/trace_irqsoff.c | 22 +++++++++++++++++++---
 1 file changed, 19 insertions(+), 3 deletions(-)

diff --git a/kernel/trace/trace_irqsoff.c b/kernel/trace/trace_irqsoff.c
index 03ecb4465ee4..f8daa754cce2 100644
--- a/kernel/trace/trace_irqsoff.c
+++ b/kernel/trace/trace_irqsoff.c
@@ -634,7 +634,7 @@ static int __irqsoff_tracer_init(struct trace_array *tr)
 	return 0;
 }
 
-static void irqsoff_tracer_reset(struct trace_array *tr)
+static void __irqsoff_tracer_reset(struct trace_array *tr)
 {
 	int lat_flag = save_flags & TRACE_ITER_LATENCY_FMT;
 	int overwrite_flag = save_flags & TRACE_ITER_OVERWRITE;
@@ -665,6 +665,12 @@ static int irqsoff_tracer_init(struct trace_array *tr)
 
 	return __irqsoff_tracer_init(tr);
 }
+
+static void irqsoff_tracer_reset(struct trace_array *tr)
+{
+	__irqsoff_tracer_reset(tr);
+}
+
 static struct tracer irqsoff_tracer __read_mostly =
 {
 	.name		= "irqsoff",
@@ -697,11 +703,16 @@ static int preemptoff_tracer_init(struct trace_array *tr)
 	return __irqsoff_tracer_init(tr);
 }
 
+static void preemptoff_tracer_reset(struct trace_array *tr)
+{
+	__irqsoff_tracer_reset(tr);
+}
+
 static struct tracer preemptoff_tracer __read_mostly =
 {
 	.name		= "preemptoff",
 	.init		= preemptoff_tracer_init,
-	.reset		= irqsoff_tracer_reset,
+	.reset		= preemptoff_tracer_reset,
 	.start		= irqsoff_tracer_start,
 	.stop		= irqsoff_tracer_stop,
 	.print_max	= true,
@@ -731,11 +742,16 @@ static int preemptirqsoff_tracer_init(struct trace_array *tr)
 	return __irqsoff_tracer_init(tr);
 }
 
+static void preemptirqsoff_tracer_reset(struct trace_array *tr)
+{
+	__irqsoff_tracer_reset(tr);
+}
+
 static struct tracer preemptirqsoff_tracer __read_mostly =
 {
 	.name		= "preemptirqsoff",
 	.init		= preemptirqsoff_tracer_init,
-	.reset		= irqsoff_tracer_reset,
+	.reset		= preemptirqsoff_tracer_reset,
 	.start		= irqsoff_tracer_start,
 	.stop		= irqsoff_tracer_stop,
 	.print_max	= true,
-- 
2.17.0.441.gb46fe60e1d-goog

^ permalink raw reply	[flat|nested] 33+ messages in thread

* [PATCH v7 4/8] trace/irqsoff: Split reset into separate functions
@ 2018-05-24  1:21   ` joelaf
  0 siblings, 0 replies; 33+ messages in thread
From: joelaf @ 2018-05-24  1:21 UTC (permalink / raw)


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

Split reset functions into seperate functions in preparation
of future patches that need to do tracer specific reset.

Signed-off-by: Joel Fernandes (Google) <joel at joelfernandes.org>
---
 kernel/trace/trace_irqsoff.c | 22 +++++++++++++++++++---
 1 file changed, 19 insertions(+), 3 deletions(-)

diff --git a/kernel/trace/trace_irqsoff.c b/kernel/trace/trace_irqsoff.c
index 03ecb4465ee4..f8daa754cce2 100644
--- a/kernel/trace/trace_irqsoff.c
+++ b/kernel/trace/trace_irqsoff.c
@@ -634,7 +634,7 @@ static int __irqsoff_tracer_init(struct trace_array *tr)
 	return 0;
 }
 
-static void irqsoff_tracer_reset(struct trace_array *tr)
+static void __irqsoff_tracer_reset(struct trace_array *tr)
 {
 	int lat_flag = save_flags & TRACE_ITER_LATENCY_FMT;
 	int overwrite_flag = save_flags & TRACE_ITER_OVERWRITE;
@@ -665,6 +665,12 @@ static int irqsoff_tracer_init(struct trace_array *tr)
 
 	return __irqsoff_tracer_init(tr);
 }
+
+static void irqsoff_tracer_reset(struct trace_array *tr)
+{
+	__irqsoff_tracer_reset(tr);
+}
+
 static struct tracer irqsoff_tracer __read_mostly =
 {
 	.name		= "irqsoff",
@@ -697,11 +703,16 @@ static int preemptoff_tracer_init(struct trace_array *tr)
 	return __irqsoff_tracer_init(tr);
 }
 
+static void preemptoff_tracer_reset(struct trace_array *tr)
+{
+	__irqsoff_tracer_reset(tr);
+}
+
 static struct tracer preemptoff_tracer __read_mostly =
 {
 	.name		= "preemptoff",
 	.init		= preemptoff_tracer_init,
-	.reset		= irqsoff_tracer_reset,
+	.reset		= preemptoff_tracer_reset,
 	.start		= irqsoff_tracer_start,
 	.stop		= irqsoff_tracer_stop,
 	.print_max	= true,
@@ -731,11 +742,16 @@ static int preemptirqsoff_tracer_init(struct trace_array *tr)
 	return __irqsoff_tracer_init(tr);
 }
 
+static void preemptirqsoff_tracer_reset(struct trace_array *tr)
+{
+	__irqsoff_tracer_reset(tr);
+}
+
 static struct tracer preemptirqsoff_tracer __read_mostly =
 {
 	.name		= "preemptirqsoff",
 	.init		= preemptirqsoff_tracer_init,
-	.reset		= irqsoff_tracer_reset,
+	.reset		= preemptirqsoff_tracer_reset,
 	.start		= irqsoff_tracer_start,
 	.stop		= irqsoff_tracer_stop,
 	.print_max	= true,
-- 
2.17.0.441.gb46fe60e1d-goog

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^ permalink raw reply	[flat|nested] 33+ messages in thread

* [PATCH v7 4/8] trace/irqsoff: Split reset into separate functions
@ 2018-05-24  1:21   ` joelaf
  0 siblings, 0 replies; 33+ messages in thread
From: Joel Fernandes @ 2018-05-24  1:21 UTC (permalink / raw)


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

Split reset functions into seperate functions in preparation
of future patches that need to do tracer specific reset.

Signed-off-by: Joel Fernandes (Google) <joel at joelfernandes.org>
---
 kernel/trace/trace_irqsoff.c | 22 +++++++++++++++++++---
 1 file changed, 19 insertions(+), 3 deletions(-)

diff --git a/kernel/trace/trace_irqsoff.c b/kernel/trace/trace_irqsoff.c
index 03ecb4465ee4..f8daa754cce2 100644
--- a/kernel/trace/trace_irqsoff.c
+++ b/kernel/trace/trace_irqsoff.c
@@ -634,7 +634,7 @@ static int __irqsoff_tracer_init(struct trace_array *tr)
 	return 0;
 }
 
-static void irqsoff_tracer_reset(struct trace_array *tr)
+static void __irqsoff_tracer_reset(struct trace_array *tr)
 {
 	int lat_flag = save_flags & TRACE_ITER_LATENCY_FMT;
 	int overwrite_flag = save_flags & TRACE_ITER_OVERWRITE;
@@ -665,6 +665,12 @@ static int irqsoff_tracer_init(struct trace_array *tr)
 
 	return __irqsoff_tracer_init(tr);
 }
+
+static void irqsoff_tracer_reset(struct trace_array *tr)
+{
+	__irqsoff_tracer_reset(tr);
+}
+
 static struct tracer irqsoff_tracer __read_mostly =
 {
 	.name		= "irqsoff",
@@ -697,11 +703,16 @@ static int preemptoff_tracer_init(struct trace_array *tr)
 	return __irqsoff_tracer_init(tr);
 }
 
+static void preemptoff_tracer_reset(struct trace_array *tr)
+{
+	__irqsoff_tracer_reset(tr);
+}
+
 static struct tracer preemptoff_tracer __read_mostly =
 {
 	.name		= "preemptoff",
 	.init		= preemptoff_tracer_init,
-	.reset		= irqsoff_tracer_reset,
+	.reset		= preemptoff_tracer_reset,
 	.start		= irqsoff_tracer_start,
 	.stop		= irqsoff_tracer_stop,
 	.print_max	= true,
@@ -731,11 +742,16 @@ static int preemptirqsoff_tracer_init(struct trace_array *tr)
 	return __irqsoff_tracer_init(tr);
 }
 
+static void preemptirqsoff_tracer_reset(struct trace_array *tr)
+{
+	__irqsoff_tracer_reset(tr);
+}
+
 static struct tracer preemptirqsoff_tracer __read_mostly =
 {
 	.name		= "preemptirqsoff",
 	.init		= preemptirqsoff_tracer_init,
-	.reset		= irqsoff_tracer_reset,
+	.reset		= preemptirqsoff_tracer_reset,
 	.start		= irqsoff_tracer_start,
 	.stop		= irqsoff_tracer_stop,
 	.print_max	= true,
-- 
2.17.0.441.gb46fe60e1d-goog

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^ permalink raw reply	[flat|nested] 33+ messages in thread

* [PATCH v7 5/8] tracepoint: Make rcuidle tracepoint callers use SRCU
  2018-05-24  1:21 ` joelaf
  (?)
@ 2018-05-24  1:21   ` joelaf
  -1 siblings, 0 replies; 33+ messages in thread
From: Joel Fernandes @ 2018-05-24  1:21 UTC (permalink / raw)
  To: linux-kernel
  Cc: kernel-team, Joel Fernandes (Google),
	Boqun Feng, Byungchul Park, Erick Reyes, Ingo Molnar,
	Julia Cartwright, linux-kselftest, Masami Hiramatsu,
	Mathieu Desnoyers, Namhyung Kim, Paul McKenney, Peter Zijlstra,
	Shuah Khan, Steven Rostedt, Thomas Glexiner, Todd Kjos,
	Tom Zanussi

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

In recent tests with IRQ on/off tracepoints, a large performance
overhead ~10% is noticed when running hackbench. This is root caused to
calls to rcu_irq_enter_irqson and rcu_irq_exit_irqson from the
tracepoint code. Following a long discussion on the list [1] about this,
we concluded that srcu is a better alternative for use during rcu idle.
Although it does involve extra barriers, its lighter than the sched-rcu
version which has to do additional RCU calls to notify RCU idle about
entry into RCU sections.

In this patch, we change the underlying implementation of the
trace_*_rcuidle API to use SRCU. This has shown to improve performance
alot for the high frequency irq enable/disable tracepoints.

Test: Tested idle and preempt/irq tracepoints.

Here are some performance numbers:

With a run of the following 30 times on a single core x86 Qemu instance
with 1GB memory:
hackbench -g 4 -f 2 -l 3000

Completion times in seconds. CONFIG_PROVE_LOCKING=y.

No patches (without this series)
Mean: 3.048
Median: 3.025
Std Dev: 0.064

With Lockdep using irq tracepoints with RCU implementation:
Mean: 3.451   (-11.66 %)
Median: 3.447 (-12.22%)
Std Dev: 0.049

With Lockdep using irq tracepoints with SRCU implementation (this series):
Mean: 3.020   (I would consider the improvement against the "without
	       this series" case as just noise).
Median: 3.013
Std Dev: 0.033

[1] https://patchwork.kernel.org/patch/10344297/

Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
---
 include/linux/tracepoint.h | 48 +++++++++++++++++++++++++++++++-------
 kernel/tracepoint.c        | 15 +++++++++++-
 2 files changed, 54 insertions(+), 9 deletions(-)

diff --git a/include/linux/tracepoint.h b/include/linux/tracepoint.h
index c94f466d57ef..880794207921 100644
--- a/include/linux/tracepoint.h
+++ b/include/linux/tracepoint.h
@@ -15,6 +15,7 @@
  */
 
 #include <linux/smp.h>
+#include <linux/srcu.h>
 #include <linux/errno.h>
 #include <linux/types.h>
 #include <linux/cpumask.h>
@@ -33,6 +34,8 @@ struct trace_eval_map {
 
 #define TRACEPOINT_DEFAULT_PRIO	10
 
+extern struct srcu_struct tracepoint_srcu;
+
 extern int
 tracepoint_probe_register(struct tracepoint *tp, void *probe, void *data);
 extern int
@@ -75,10 +78,15 @@ int unregister_tracepoint_module_notifier(struct notifier_block *nb)
  * probe unregistration and the end of module exit to make sure there is no
  * caller executing a probe when it is freed.
  */
+#ifdef CONFIG_TRACEPOINTS
 static inline void tracepoint_synchronize_unregister(void)
 {
+	synchronize_srcu(&tracepoint_srcu);
 	synchronize_sched();
 }
+#else
+static inline void tracepoint_synchronize_unregister(void) { }
+#endif
 
 #ifdef CONFIG_HAVE_SYSCALL_TRACEPOINTS
 extern int syscall_regfunc(void);
@@ -129,18 +137,38 @@ extern void syscall_unregfunc(void);
  * as "(void *, void)". The DECLARE_TRACE_NOARGS() will pass in just
  * "void *data", where as the DECLARE_TRACE() will pass in "void *data, proto".
  */
-#define __DO_TRACE(tp, proto, args, cond, rcucheck)			\
+#define __DO_TRACE(tp, proto, args, cond, rcuidle)			\
 	do {								\
 		struct tracepoint_func *it_func_ptr;			\
 		void *it_func;						\
 		void *__data;						\
+		int __maybe_unused idx = 0;				\
 									\
 		if (!(cond))						\
 			return;						\
-		if (rcucheck)						\
-			rcu_irq_enter_irqson();				\
-		rcu_read_lock_sched_notrace();				\
-		it_func_ptr = rcu_dereference_sched((tp)->funcs);	\
+									\
+		/*							\
+		 * For rcuidle callers, use srcu since sched-rcu	\
+		 * doesn't work from the idle path.			\
+		 */							\
+		if (rcuidle) {						\
+			if (in_nmi()) {					\
+				WARN_ON_ONCE(1);			\
+				return; /* no srcu from nmi */		\
+			}						\
+									\
+			idx = srcu_read_lock_notrace(&tracepoint_srcu);	\
+			it_func_ptr =					\
+				srcu_dereference_notrace((tp)->funcs,	\
+						&tracepoint_srcu);	\
+			/* To keep it consistent with !rcuidle path */	\
+			preempt_disable_notrace();			\
+		} else {						\
+			rcu_read_lock_sched_notrace();			\
+			it_func_ptr =					\
+				rcu_dereference_sched((tp)->funcs);	\
+		}							\
+									\
 		if (it_func_ptr) {					\
 			do {						\
 				it_func = (it_func_ptr)->func;		\
@@ -148,9 +176,13 @@ extern void syscall_unregfunc(void);
 				((void(*)(proto))(it_func))(args);	\
 			} while ((++it_func_ptr)->func);		\
 		}							\
-		rcu_read_unlock_sched_notrace();			\
-		if (rcucheck)						\
-			rcu_irq_exit_irqson();				\
+									\
+		if (rcuidle) {						\
+			preempt_enable_notrace();			\
+			srcu_read_unlock_notrace(&tracepoint_srcu, idx);\
+		} else {						\
+			rcu_read_unlock_sched_notrace();		\
+		}							\
 	} while (0)
 
 #ifndef MODULE
diff --git a/kernel/tracepoint.c b/kernel/tracepoint.c
index 1e37da2e0c25..54157792f5ab 100644
--- a/kernel/tracepoint.c
+++ b/kernel/tracepoint.c
@@ -31,6 +31,9 @@
 extern struct tracepoint * const __start___tracepoints_ptrs[];
 extern struct tracepoint * const __stop___tracepoints_ptrs[];
 
+DEFINE_SRCU(tracepoint_srcu);
+EXPORT_SYMBOL_GPL(tracepoint_srcu);
+
 /* Set to 1 to enable tracepoint debug output */
 static const int tracepoint_debug;
 
@@ -67,16 +70,26 @@ static inline void *allocate_probes(int count)
 	return p == NULL ? NULL : p->probes;
 }
 
-static void rcu_free_old_probes(struct rcu_head *head)
+static void srcu_free_old_probes(struct rcu_head *head)
 {
 	kfree(container_of(head, struct tp_probes, rcu));
 }
 
+static void rcu_free_old_probes(struct rcu_head *head)
+{
+	call_srcu(&tracepoint_srcu, head, srcu_free_old_probes);
+}
+
 static inline void release_probes(struct tracepoint_func *old)
 {
 	if (old) {
 		struct tp_probes *tp_probes = container_of(old,
 			struct tp_probes, probes[0]);
+		/*
+		 * Tracepoint probes are protected by both sched RCU and SRCU,
+		 * by calling the SRCU callback in the sched RCU callback we
+		 * cover both cases. So lets chain the SRCU and RCU callbacks.
+		 */
 		call_rcu_sched(&tp_probes->rcu, rcu_free_old_probes);
 	}
 }
-- 
2.17.0.441.gb46fe60e1d-goog

^ permalink raw reply	[flat|nested] 33+ messages in thread

* [PATCH v7 5/8] tracepoint: Make rcuidle tracepoint callers use SRCU
@ 2018-05-24  1:21   ` joelaf
  0 siblings, 0 replies; 33+ messages in thread
From: joelaf @ 2018-05-24  1:21 UTC (permalink / raw)


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

In recent tests with IRQ on/off tracepoints, a large performance
overhead ~10% is noticed when running hackbench. This is root caused to
calls to rcu_irq_enter_irqson and rcu_irq_exit_irqson from the
tracepoint code. Following a long discussion on the list [1] about this,
we concluded that srcu is a better alternative for use during rcu idle.
Although it does involve extra barriers, its lighter than the sched-rcu
version which has to do additional RCU calls to notify RCU idle about
entry into RCU sections.

In this patch, we change the underlying implementation of the
trace_*_rcuidle API to use SRCU. This has shown to improve performance
alot for the high frequency irq enable/disable tracepoints.

Test: Tested idle and preempt/irq tracepoints.

Here are some performance numbers:

With a run of the following 30 times on a single core x86 Qemu instance
with 1GB memory:
hackbench -g 4 -f 2 -l 3000

Completion times in seconds. CONFIG_PROVE_LOCKING=y.

No patches (without this series)
Mean: 3.048
Median: 3.025
Std Dev: 0.064

With Lockdep using irq tracepoints with RCU implementation:
Mean: 3.451   (-11.66 %)
Median: 3.447 (-12.22%)
Std Dev: 0.049

With Lockdep using irq tracepoints with SRCU implementation (this series):
Mean: 3.020   (I would consider the improvement against the "without
	       this series" case as just noise).
Median: 3.013
Std Dev: 0.033

[1] https://patchwork.kernel.org/patch/10344297/

Signed-off-by: Joel Fernandes (Google) <joel at joelfernandes.org>
---
 include/linux/tracepoint.h | 48 +++++++++++++++++++++++++++++++-------
 kernel/tracepoint.c        | 15 +++++++++++-
 2 files changed, 54 insertions(+), 9 deletions(-)

diff --git a/include/linux/tracepoint.h b/include/linux/tracepoint.h
index c94f466d57ef..880794207921 100644
--- a/include/linux/tracepoint.h
+++ b/include/linux/tracepoint.h
@@ -15,6 +15,7 @@
  */
 
 #include <linux/smp.h>
+#include <linux/srcu.h>
 #include <linux/errno.h>
 #include <linux/types.h>
 #include <linux/cpumask.h>
@@ -33,6 +34,8 @@ struct trace_eval_map {
 
 #define TRACEPOINT_DEFAULT_PRIO	10
 
+extern struct srcu_struct tracepoint_srcu;
+
 extern int
 tracepoint_probe_register(struct tracepoint *tp, void *probe, void *data);
 extern int
@@ -75,10 +78,15 @@ int unregister_tracepoint_module_notifier(struct notifier_block *nb)
  * probe unregistration and the end of module exit to make sure there is no
  * caller executing a probe when it is freed.
  */
+#ifdef CONFIG_TRACEPOINTS
 static inline void tracepoint_synchronize_unregister(void)
 {
+	synchronize_srcu(&tracepoint_srcu);
 	synchronize_sched();
 }
+#else
+static inline void tracepoint_synchronize_unregister(void) { }
+#endif
 
 #ifdef CONFIG_HAVE_SYSCALL_TRACEPOINTS
 extern int syscall_regfunc(void);
@@ -129,18 +137,38 @@ extern void syscall_unregfunc(void);
  * as "(void *, void)". The DECLARE_TRACE_NOARGS() will pass in just
  * "void *data", where as the DECLARE_TRACE() will pass in "void *data, proto".
  */
-#define __DO_TRACE(tp, proto, args, cond, rcucheck)			\
+#define __DO_TRACE(tp, proto, args, cond, rcuidle)			\
 	do {								\
 		struct tracepoint_func *it_func_ptr;			\
 		void *it_func;						\
 		void *__data;						\
+		int __maybe_unused idx = 0;				\
 									\
 		if (!(cond))						\
 			return;						\
-		if (rcucheck)						\
-			rcu_irq_enter_irqson();				\
-		rcu_read_lock_sched_notrace();				\
-		it_func_ptr = rcu_dereference_sched((tp)->funcs);	\
+									\
+		/*							\
+		 * For rcuidle callers, use srcu since sched-rcu	\
+		 * doesn't work from the idle path.			\
+		 */							\
+		if (rcuidle) {						\
+			if (in_nmi()) {					\
+				WARN_ON_ONCE(1);			\
+				return; /* no srcu from nmi */		\
+			}						\
+									\
+			idx = srcu_read_lock_notrace(&tracepoint_srcu);	\
+			it_func_ptr =					\
+				srcu_dereference_notrace((tp)->funcs,	\
+						&tracepoint_srcu);	\
+			/* To keep it consistent with !rcuidle path */	\
+			preempt_disable_notrace();			\
+		} else {						\
+			rcu_read_lock_sched_notrace();			\
+			it_func_ptr =					\
+				rcu_dereference_sched((tp)->funcs);	\
+		}							\
+									\
 		if (it_func_ptr) {					\
 			do {						\
 				it_func = (it_func_ptr)->func;		\
@@ -148,9 +176,13 @@ extern void syscall_unregfunc(void);
 				((void(*)(proto))(it_func))(args);	\
 			} while ((++it_func_ptr)->func);		\
 		}							\
-		rcu_read_unlock_sched_notrace();			\
-		if (rcucheck)						\
-			rcu_irq_exit_irqson();				\
+									\
+		if (rcuidle) {						\
+			preempt_enable_notrace();			\
+			srcu_read_unlock_notrace(&tracepoint_srcu, idx);\
+		} else {						\
+			rcu_read_unlock_sched_notrace();		\
+		}							\
 	} while (0)
 
 #ifndef MODULE
diff --git a/kernel/tracepoint.c b/kernel/tracepoint.c
index 1e37da2e0c25..54157792f5ab 100644
--- a/kernel/tracepoint.c
+++ b/kernel/tracepoint.c
@@ -31,6 +31,9 @@
 extern struct tracepoint * const __start___tracepoints_ptrs[];
 extern struct tracepoint * const __stop___tracepoints_ptrs[];
 
+DEFINE_SRCU(tracepoint_srcu);
+EXPORT_SYMBOL_GPL(tracepoint_srcu);
+
 /* Set to 1 to enable tracepoint debug output */
 static const int tracepoint_debug;
 
@@ -67,16 +70,26 @@ static inline void *allocate_probes(int count)
 	return p == NULL ? NULL : p->probes;
 }
 
-static void rcu_free_old_probes(struct rcu_head *head)
+static void srcu_free_old_probes(struct rcu_head *head)
 {
 	kfree(container_of(head, struct tp_probes, rcu));
 }
 
+static void rcu_free_old_probes(struct rcu_head *head)
+{
+	call_srcu(&tracepoint_srcu, head, srcu_free_old_probes);
+}
+
 static inline void release_probes(struct tracepoint_func *old)
 {
 	if (old) {
 		struct tp_probes *tp_probes = container_of(old,
 			struct tp_probes, probes[0]);
+		/*
+		 * Tracepoint probes are protected by both sched RCU and SRCU,
+		 * by calling the SRCU callback in the sched RCU callback we
+		 * cover both cases. So lets chain the SRCU and RCU callbacks.
+		 */
 		call_rcu_sched(&tp_probes->rcu, rcu_free_old_probes);
 	}
 }
-- 
2.17.0.441.gb46fe60e1d-goog

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^ permalink raw reply	[flat|nested] 33+ messages in thread

* [PATCH v7 5/8] tracepoint: Make rcuidle tracepoint callers use SRCU
@ 2018-05-24  1:21   ` joelaf
  0 siblings, 0 replies; 33+ messages in thread
From: Joel Fernandes @ 2018-05-24  1:21 UTC (permalink / raw)


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

In recent tests with IRQ on/off tracepoints, a large performance
overhead ~10% is noticed when running hackbench. This is root caused to
calls to rcu_irq_enter_irqson and rcu_irq_exit_irqson from the
tracepoint code. Following a long discussion on the list [1] about this,
we concluded that srcu is a better alternative for use during rcu idle.
Although it does involve extra barriers, its lighter than the sched-rcu
version which has to do additional RCU calls to notify RCU idle about
entry into RCU sections.

In this patch, we change the underlying implementation of the
trace_*_rcuidle API to use SRCU. This has shown to improve performance
alot for the high frequency irq enable/disable tracepoints.

Test: Tested idle and preempt/irq tracepoints.

Here are some performance numbers:

With a run of the following 30 times on a single core x86 Qemu instance
with 1GB memory:
hackbench -g 4 -f 2 -l 3000

Completion times in seconds. CONFIG_PROVE_LOCKING=y.

No patches (without this series)
Mean: 3.048
Median: 3.025
Std Dev: 0.064

With Lockdep using irq tracepoints with RCU implementation:
Mean: 3.451   (-11.66 %)
Median: 3.447 (-12.22%)
Std Dev: 0.049

With Lockdep using irq tracepoints with SRCU implementation (this series):
Mean: 3.020   (I would consider the improvement against the "without
	       this series" case as just noise).
Median: 3.013
Std Dev: 0.033

[1] https://patchwork.kernel.org/patch/10344297/

Signed-off-by: Joel Fernandes (Google) <joel at joelfernandes.org>
---
 include/linux/tracepoint.h | 48 +++++++++++++++++++++++++++++++-------
 kernel/tracepoint.c        | 15 +++++++++++-
 2 files changed, 54 insertions(+), 9 deletions(-)

diff --git a/include/linux/tracepoint.h b/include/linux/tracepoint.h
index c94f466d57ef..880794207921 100644
--- a/include/linux/tracepoint.h
+++ b/include/linux/tracepoint.h
@@ -15,6 +15,7 @@
  */
 
 #include <linux/smp.h>
+#include <linux/srcu.h>
 #include <linux/errno.h>
 #include <linux/types.h>
 #include <linux/cpumask.h>
@@ -33,6 +34,8 @@ struct trace_eval_map {
 
 #define TRACEPOINT_DEFAULT_PRIO	10
 
+extern struct srcu_struct tracepoint_srcu;
+
 extern int
 tracepoint_probe_register(struct tracepoint *tp, void *probe, void *data);
 extern int
@@ -75,10 +78,15 @@ int unregister_tracepoint_module_notifier(struct notifier_block *nb)
  * probe unregistration and the end of module exit to make sure there is no
  * caller executing a probe when it is freed.
  */
+#ifdef CONFIG_TRACEPOINTS
 static inline void tracepoint_synchronize_unregister(void)
 {
+	synchronize_srcu(&tracepoint_srcu);
 	synchronize_sched();
 }
+#else
+static inline void tracepoint_synchronize_unregister(void) { }
+#endif
 
 #ifdef CONFIG_HAVE_SYSCALL_TRACEPOINTS
 extern int syscall_regfunc(void);
@@ -129,18 +137,38 @@ extern void syscall_unregfunc(void);
  * as "(void *, void)". The DECLARE_TRACE_NOARGS() will pass in just
  * "void *data", where as the DECLARE_TRACE() will pass in "void *data, proto".
  */
-#define __DO_TRACE(tp, proto, args, cond, rcucheck)			\
+#define __DO_TRACE(tp, proto, args, cond, rcuidle)			\
 	do {								\
 		struct tracepoint_func *it_func_ptr;			\
 		void *it_func;						\
 		void *__data;						\
+		int __maybe_unused idx = 0;				\
 									\
 		if (!(cond))						\
 			return;						\
-		if (rcucheck)						\
-			rcu_irq_enter_irqson();				\
-		rcu_read_lock_sched_notrace();				\
-		it_func_ptr = rcu_dereference_sched((tp)->funcs);	\
+									\
+		/*							\
+		 * For rcuidle callers, use srcu since sched-rcu	\
+		 * doesn't work from the idle path.			\
+		 */							\
+		if (rcuidle) {						\
+			if (in_nmi()) {					\
+				WARN_ON_ONCE(1);			\
+				return; /* no srcu from nmi */		\
+			}						\
+									\
+			idx = srcu_read_lock_notrace(&tracepoint_srcu);	\
+			it_func_ptr =					\
+				srcu_dereference_notrace((tp)->funcs,	\
+						&tracepoint_srcu);	\
+			/* To keep it consistent with !rcuidle path */	\
+			preempt_disable_notrace();			\
+		} else {						\
+			rcu_read_lock_sched_notrace();			\
+			it_func_ptr =					\
+				rcu_dereference_sched((tp)->funcs);	\
+		}							\
+									\
 		if (it_func_ptr) {					\
 			do {						\
 				it_func = (it_func_ptr)->func;		\
@@ -148,9 +176,13 @@ extern void syscall_unregfunc(void);
 				((void(*)(proto))(it_func))(args);	\
 			} while ((++it_func_ptr)->func);		\
 		}							\
-		rcu_read_unlock_sched_notrace();			\
-		if (rcucheck)						\
-			rcu_irq_exit_irqson();				\
+									\
+		if (rcuidle) {						\
+			preempt_enable_notrace();			\
+			srcu_read_unlock_notrace(&tracepoint_srcu, idx);\
+		} else {						\
+			rcu_read_unlock_sched_notrace();		\
+		}							\
 	} while (0)
 
 #ifndef MODULE
diff --git a/kernel/tracepoint.c b/kernel/tracepoint.c
index 1e37da2e0c25..54157792f5ab 100644
--- a/kernel/tracepoint.c
+++ b/kernel/tracepoint.c
@@ -31,6 +31,9 @@
 extern struct tracepoint * const __start___tracepoints_ptrs[];
 extern struct tracepoint * const __stop___tracepoints_ptrs[];
 
+DEFINE_SRCU(tracepoint_srcu);
+EXPORT_SYMBOL_GPL(tracepoint_srcu);
+
 /* Set to 1 to enable tracepoint debug output */
 static const int tracepoint_debug;
 
@@ -67,16 +70,26 @@ static inline void *allocate_probes(int count)
 	return p == NULL ? NULL : p->probes;
 }
 
-static void rcu_free_old_probes(struct rcu_head *head)
+static void srcu_free_old_probes(struct rcu_head *head)
 {
 	kfree(container_of(head, struct tp_probes, rcu));
 }
 
+static void rcu_free_old_probes(struct rcu_head *head)
+{
+	call_srcu(&tracepoint_srcu, head, srcu_free_old_probes);
+}
+
 static inline void release_probes(struct tracepoint_func *old)
 {
 	if (old) {
 		struct tp_probes *tp_probes = container_of(old,
 			struct tp_probes, probes[0]);
+		/*
+		 * Tracepoint probes are protected by both sched RCU and SRCU,
+		 * by calling the SRCU callback in the sched RCU callback we
+		 * cover both cases. So lets chain the SRCU and RCU callbacks.
+		 */
 		call_rcu_sched(&tp_probes->rcu, rcu_free_old_probes);
 	}
 }
-- 
2.17.0.441.gb46fe60e1d-goog

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^ permalink raw reply	[flat|nested] 33+ messages in thread

* [PATCH v7 6/8] tracing: Centralize preemptirq tracepoints and unify their usage
  2018-05-24  1:21 ` joelaf
  (?)
@ 2018-05-24  1:21   ` joelaf
  -1 siblings, 0 replies; 33+ messages in thread
From: Joel Fernandes @ 2018-05-24  1:21 UTC (permalink / raw)
  To: linux-kernel
  Cc: kernel-team, Joel Fernandes (Google),
	Boqun Feng, Byungchul Park, Erick Reyes, Ingo Molnar,
	Julia Cartwright, linux-kselftest, Masami Hiramatsu,
	Mathieu Desnoyers, Namhyung Kim, Paul McKenney, Peter Zijlstra,
	Shuah Khan, Steven Rostedt, Thomas Glexiner, Todd Kjos,
	Tom Zanussi

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

This patch detaches the preemptirq tracepoints from the tracers and
keeps it separate.

Advantages:
* Lockdep and irqsoff event can now run in parallel since they no longer
have their own calls.

* This unifies the usecase of adding hooks to an irqsoff and irqson
event, and a preemptoff and preempton event.
  3 users of the events exist:
  - Lockdep
  - irqsoff and preemptoff tracers
  - irqs and preempt trace events

The unification cleans up several ifdefs and makes the code in preempt
tracer and irqsoff tracers simpler. It gets rid of all the horrific
ifdeferry around PROVE_LOCKING and makes configuration of the different
users of the tracepoints more easy and understandable. It also gets rid
of the time_* function calls from the lockdep hooks used to call into
the preemptirq tracer which is not needed anymore. The negative delta in
lines of code in this patch is quite large too.

In the patch we introduce a new CONFIG option PREEMPTIRQ_TRACEPOINTS
as a single point for registering probes onto the tracepoints. With
this,
the web of config options for preempt/irq toggle tracepoints and its
users becomes:

 PREEMPT_TRACER   PREEMPTIRQ_EVENTS  IRQSOFF_TRACER PROVE_LOCKING
       |                 |     \         |           |
       \    (selects)    /      \        \ (selects) /
      TRACE_PREEMPT_TOGGLE       ----> TRACE_IRQFLAGS
                      \                  /
                       \ (depends on)   /
                     PREEMPTIRQ_TRACEPOINTS

One note, I have to check for lockdep recursion in the code that calls
the trace events API and bail out if we're in lockdep recursion
protection to prevent something like the following case: a spin_lock is
taken. Then lockdep_acquired is called.  That does a raw_local_irq_save
and then sets lockdep_recursion, and then calls __lockdep_acquired. In
this function, a call to get_lock_stats happens which calls
preempt_disable, which calls trace IRQS off somewhere which enters my
tracepoint code and sets the tracing_irq_cpu flag to prevent recursion.
This flag is then never cleared causing lockdep paths to never be
entered and thus causing splats and other bad things.

Other than the performance tests mentioned in the previous patch, I also
ran the locking API test suite. I verified that all tests cases are
passing.

I also injected issues by not registering lockdep probes onto the
tracepoints and I see failures to confirm that the probes are indeed
working.

Without probes:

[    0.000000]      hard-irqs-on + irq-safe-A/21:  ok  |  ok  |  ok  |
[    0.000000]      soft-irqs-on + irq-safe-A/21:  ok  |  ok  |  ok  |
[    0.000000]        sirq-safe-A => hirqs-on/12:  ok  |  ok  |  ok  |
[    0.000000]        sirq-safe-A => hirqs-on/21:  ok  |  ok  |  ok  |
[    0.000000]          hard-safe-A + irqs-on/12:  ok  |  ok  |  ok  |
[    0.000000]          soft-safe-A + irqs-on/12:  ok  |  ok  |  ok  |
[    0.000000]          hard-safe-A + irqs-on/21:  ok  |  ok  |  ok  |
[    0.000000]          soft-safe-A + irqs-on/21:  ok  |  ok  |  ok  |
[    0.000000]     hard-safe-A + unsafe-B #1/123:  ok  |  ok  |  ok  |
[    0.000000]     soft-safe-A + unsafe-B #1/123:  ok  |  ok  |  ok  |

With probes:

[    0.000000]      hard-irqs-on + irq-safe-A/21:  ok  |  ok  |  ok  |
[    0.000000]      soft-irqs-on + irq-safe-A/21:  ok  |  ok  |  ok  |
[    0.000000]        sirq-safe-A => hirqs-on/12:FAILED|FAILED|  ok  |
[    0.000000]        sirq-safe-A => hirqs-on/21:FAILED|FAILED|  ok  |
[    0.000000]          hard-safe-A + irqs-on/12:FAILED|FAILED|  ok  |
[    0.000000]          soft-safe-A + irqs-on/12:FAILED|FAILED|  ok  |
[    0.000000]          hard-safe-A + irqs-on/21:FAILED|FAILED|  ok  |
[    0.000000]          soft-safe-A + irqs-on/21:FAILED|FAILED|  ok  |
[    0.000000]     hard-safe-A + unsafe-B #1/123:  ok  |  ok  |  ok  |
[    0.000000]     soft-safe-A + unsafe-B #1/123:  ok  |  ok  |  ok  |

Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
---
 include/linux/ftrace.h            |  11 +-
 include/linux/irqflags.h          |  11 +-
 include/linux/lockdep.h           |   8 +-
 include/linux/preempt.h           |   2 +-
 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      | 213 ++++++++----------------------
 kernel/trace/trace_preemptirq.c   |  71 ++++++++++
 12 files changed, 189 insertions(+), 216 deletions(-)
 create mode 100644 kernel/trace/trace_preemptirq.c

diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
index 9c3c9a319e48..5191030af0c0 100644
--- a/include/linux/ftrace.h
+++ b/include/linux/ftrace.h
@@ -709,16 +709,7 @@ static inline unsigned long get_lock_parent_ip(void)
 	return CALLER_ADDR2;
 }
 
-#ifdef CONFIG_IRQSOFF_TRACER
-  extern void time_hardirqs_on(unsigned long a0, unsigned long a1);
-  extern void time_hardirqs_off(unsigned long a0, unsigned long a1);
-#else
-  static inline void time_hardirqs_on(unsigned long a0, unsigned long a1) { }
-  static inline void time_hardirqs_off(unsigned long a0, unsigned long a1) { }
-#endif
-
-#if defined(CONFIG_PREEMPT_TRACER) || \
-	(defined(CONFIG_DEBUG_PREEMPT) && defined(CONFIG_PREEMPTIRQ_EVENTS))
+#ifdef CONFIG_TRACE_PREEMPT_TOGGLE
   extern void trace_preempt_on(unsigned long a0, unsigned long a1);
   extern void trace_preempt_off(unsigned long a0, unsigned long a1);
 #else
diff --git a/include/linux/irqflags.h b/include/linux/irqflags.h
index 9700f00bbc04..50edb9cbbd26 100644
--- a/include/linux/irqflags.h
+++ b/include/linux/irqflags.h
@@ -15,9 +15,16 @@
 #include <linux/typecheck.h>
 #include <asm/irqflags.h>
 
-#ifdef CONFIG_TRACE_IRQFLAGS
+/* Currently trace_softirqs_on/off is used only by lockdep */
+#ifdef CONFIG_PROVE_LOCKING
   extern void trace_softirqs_on(unsigned long ip);
   extern void trace_softirqs_off(unsigned long ip);
+#else
+# define trace_softirqs_on(ip)	do { } while (0)
+# define trace_softirqs_off(ip)	do { } while (0)
+#endif
+
+#ifdef CONFIG_TRACE_IRQFLAGS
   extern void trace_hardirqs_on(void);
   extern void trace_hardirqs_off(void);
 # define trace_hardirq_context(p)	((p)->hardirq_context)
@@ -43,8 +50,6 @@ do {						\
 #else
 # define trace_hardirqs_on()		do { } while (0)
 # define trace_hardirqs_off()		do { } while (0)
-# define trace_softirqs_on(ip)		do { } while (0)
-# define trace_softirqs_off(ip)		do { } while (0)
 # define trace_hardirq_context(p)	0
 # define trace_softirq_context(p)	0
 # define trace_hardirqs_enabled(p)	0
diff --git a/include/linux/lockdep.h b/include/linux/lockdep.h
index 6fc77d4dbdcd..a8113357ceeb 100644
--- a/include/linux/lockdep.h
+++ b/include/linux/lockdep.h
@@ -266,7 +266,8 @@ struct held_lock {
 /*
  * Initialization, self-test and debugging-output methods:
  */
-extern void lockdep_info(void);
+extern void lockdep_init(void);
+extern void lockdep_init_early(void);
 extern void lockdep_reset(void);
 extern void lockdep_reset_lock(struct lockdep_map *lock);
 extern void lockdep_free_key_range(void *start, unsigned long size);
@@ -406,7 +407,8 @@ static inline void lockdep_on(void)
 # define lock_downgrade(l, i)			do { } while (0)
 # define lock_set_class(l, n, k, s, i)		do { } while (0)
 # define lock_set_subclass(l, s, i)		do { } while (0)
-# define lockdep_info()				do { } while (0)
+# define lockdep_init()				do { } while (0)
+# define lockdep_init_early()			do { } while (0)
 # define lockdep_init_map(lock, name, key, sub) \
 		do { (void)(name); (void)(key); } while (0)
 # define lockdep_set_class(lock, key)		do { (void)(key); } while (0)
@@ -532,7 +534,7 @@ do {								\
 
 #endif /* CONFIG_LOCKDEP */
 
-#ifdef CONFIG_TRACE_IRQFLAGS
+#ifdef CONFIG_PROVE_LOCKING
 extern void print_irqtrace_events(struct task_struct *curr);
 #else
 static inline void print_irqtrace_events(struct task_struct *curr)
diff --git a/include/linux/preempt.h b/include/linux/preempt.h
index 5bd3f151da78..c01813c3fbe9 100644
--- a/include/linux/preempt.h
+++ b/include/linux/preempt.h
@@ -150,7 +150,7 @@
  */
 #define in_atomic_preempt_off() (preempt_count() != PREEMPT_DISABLE_OFFSET)
 
-#if defined(CONFIG_DEBUG_PREEMPT) || defined(CONFIG_PREEMPT_TRACER)
+#if defined(CONFIG_DEBUG_PREEMPT) || defined(CONFIG_TRACE_PREEMPT_TOGGLE)
 extern void preempt_count_add(int val);
 extern void preempt_count_sub(int val);
 #define preempt_count_dec_and_test() \
diff --git a/include/trace/events/preemptirq.h b/include/trace/events/preemptirq.h
index 9c4eb33c5a1d..9a0d4ceeb166 100644
--- a/include/trace/events/preemptirq.h
+++ b/include/trace/events/preemptirq.h
@@ -1,4 +1,4 @@
-#ifdef CONFIG_PREEMPTIRQ_EVENTS
+#ifdef CONFIG_PREEMPTIRQ_TRACEPOINTS
 
 #undef TRACE_SYSTEM
 #define TRACE_SYSTEM preemptirq
@@ -32,7 +32,7 @@ DECLARE_EVENT_CLASS(preemptirq_template,
 		  (void *)((unsigned long)(_stext) + __entry->parent_offs))
 );
 
-#ifndef CONFIG_PROVE_LOCKING
+#ifdef CONFIG_TRACE_IRQFLAGS
 DEFINE_EVENT(preemptirq_template, irq_disable,
 	     TP_PROTO(unsigned long ip, unsigned long parent_ip),
 	     TP_ARGS(ip, parent_ip));
@@ -40,9 +40,14 @@ DEFINE_EVENT(preemptirq_template, irq_disable,
 DEFINE_EVENT(preemptirq_template, irq_enable,
 	     TP_PROTO(unsigned long ip, unsigned long parent_ip),
 	     TP_ARGS(ip, parent_ip));
+#else
+#define trace_irq_enable(...)
+#define trace_irq_disable(...)
+#define trace_irq_enable_rcuidle(...)
+#define trace_irq_disable_rcuidle(...)
 #endif
 
-#ifdef CONFIG_DEBUG_PREEMPT
+#ifdef CONFIG_TRACE_PREEMPT_TOGGLE
 DEFINE_EVENT(preemptirq_template, preempt_disable,
 	     TP_PROTO(unsigned long ip, unsigned long parent_ip),
 	     TP_ARGS(ip, parent_ip));
@@ -50,22 +55,22 @@ DEFINE_EVENT(preemptirq_template, preempt_disable,
 DEFINE_EVENT(preemptirq_template, preempt_enable,
 	     TP_PROTO(unsigned long ip, unsigned long parent_ip),
 	     TP_ARGS(ip, parent_ip));
+#else
+#define trace_preempt_enable(...)
+#define trace_preempt_disable(...)
+#define trace_preempt_enable_rcuidle(...)
+#define trace_preempt_disable_rcuidle(...)
 #endif
 
 #endif /* _TRACE_PREEMPTIRQ_H */
 
 #include <trace/define_trace.h>
 
-#endif /* !CONFIG_PREEMPTIRQ_EVENTS */
-
-#if !defined(CONFIG_PREEMPTIRQ_EVENTS) || defined(CONFIG_PROVE_LOCKING)
+#else /* !CONFIG_PREEMPTIRQ_TRACEPOINTS */
 #define trace_irq_enable(...)
 #define trace_irq_disable(...)
 #define trace_irq_enable_rcuidle(...)
 #define trace_irq_disable_rcuidle(...)
-#endif
-
-#if !defined(CONFIG_PREEMPTIRQ_EVENTS) || !defined(CONFIG_DEBUG_PREEMPT)
 #define trace_preempt_enable(...)
 #define trace_preempt_disable(...)
 #define trace_preempt_enable_rcuidle(...)
diff --git a/init/main.c b/init/main.c
index fd37315835b4..5181c5bc2f0c 100644
--- a/init/main.c
+++ b/init/main.c
@@ -647,6 +647,9 @@ asmlinkage __visible void __init start_kernel(void)
 	profile_init();
 	call_function_init();
 	WARN(!irqs_disabled(), "Interrupts were enabled early\n");
+
+	lockdep_init_early();
+
 	early_boot_irqs_disabled = false;
 	local_irq_enable();
 
@@ -662,7 +665,7 @@ asmlinkage __visible void __init start_kernel(void)
 		panic("Too many boot %s vars at `%s'", panic_later,
 		      panic_param);
 
-	lockdep_info();
+	lockdep_init();
 
 	/*
 	 * Need to run this when irqs are enabled, because it wants
diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index 023386338269..871a42232858 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -55,6 +55,7 @@
 
 #include "lockdep_internals.h"
 
+#include <trace/events/preemptirq.h>
 #define CREATE_TRACE_POINTS
 #include <trace/events/lock.h>
 
@@ -2841,10 +2842,9 @@ static void __trace_hardirqs_on_caller(unsigned long ip)
 	debug_atomic_inc(hardirqs_on_events);
 }
 
-__visible void trace_hardirqs_on_caller(unsigned long ip)
+static void lockdep_hardirqs_on(void *none, unsigned long ignore,
+				unsigned long ip)
 {
-	time_hardirqs_on(CALLER_ADDR0, ip);
-
 	if (unlikely(!debug_locks || current->lockdep_recursion))
 		return;
 
@@ -2883,23 +2883,15 @@ __visible void trace_hardirqs_on_caller(unsigned long ip)
 	__trace_hardirqs_on_caller(ip);
 	current->lockdep_recursion = 0;
 }
-EXPORT_SYMBOL(trace_hardirqs_on_caller);
-
-void trace_hardirqs_on(void)
-{
-	trace_hardirqs_on_caller(CALLER_ADDR0);
-}
-EXPORT_SYMBOL(trace_hardirqs_on);
 
 /*
  * Hardirqs were disabled:
  */
-__visible void trace_hardirqs_off_caller(unsigned long ip)
+static void lockdep_hardirqs_off(void *none, unsigned long ignore,
+				 unsigned long ip)
 {
 	struct task_struct *curr = current;
 
-	time_hardirqs_off(CALLER_ADDR0, ip);
-
 	if (unlikely(!debug_locks || current->lockdep_recursion))
 		return;
 
@@ -2921,13 +2913,6 @@ __visible void trace_hardirqs_off_caller(unsigned long ip)
 	} else
 		debug_atomic_inc(redundant_hardirqs_off);
 }
-EXPORT_SYMBOL(trace_hardirqs_off_caller);
-
-void trace_hardirqs_off(void)
-{
-	trace_hardirqs_off_caller(CALLER_ADDR0);
-}
-EXPORT_SYMBOL(trace_hardirqs_off);
 
 /*
  * Softirqs will be enabled:
@@ -4334,7 +4319,15 @@ void lockdep_reset_lock(struct lockdep_map *lock)
 	raw_local_irq_restore(flags);
 }
 
-void __init lockdep_info(void)
+void __init lockdep_init_early(void)
+{
+#ifdef CONFIG_PROVE_LOCKING
+	register_trace_prio_irq_disable(lockdep_hardirqs_off, NULL, INT_MAX);
+	register_trace_prio_irq_enable(lockdep_hardirqs_on, NULL, INT_MIN);
+#endif
+}
+
+void __init lockdep_init(void)
 {
 	printk("Lock dependency validator: Copyright (c) 2006 Red Hat, Inc., Ingo Molnar\n");
 
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 092f7c4de903..4e9c2d254fba 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -3189,7 +3189,7 @@ static inline void sched_tick_stop(int cpu) { }
 #endif
 
 #if defined(CONFIG_PREEMPT) && (defined(CONFIG_DEBUG_PREEMPT) || \
-				defined(CONFIG_PREEMPT_TRACER))
+				defined(CONFIG_TRACE_PREEMPT_TOGGLE))
 /*
  * If the value passed in is equal to the current preempt count
  * then we just disabled preemption. Start timing the latency.
diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig
index c4f0f2e4126e..0bcba2a76ad9 100644
--- a/kernel/trace/Kconfig
+++ b/kernel/trace/Kconfig
@@ -82,6 +82,15 @@ config RING_BUFFER_ALLOW_SWAP
 	 Allow the use of ring_buffer_swap_cpu.
 	 Adds a very slight overhead to tracing when enabled.
 
+config PREEMPTIRQ_TRACEPOINTS
+	bool
+	depends on TRACE_PREEMPT_TOGGLE || TRACE_IRQFLAGS
+	select TRACING
+	default y
+	help
+	  Create preempt/irq toggle tracepoints if needed, so that other parts
+	  of the kernel can use them to generate or add hooks to them.
+
 # All tracer options should select GENERIC_TRACER. For those options that are
 # enabled by all tracers (context switch and event tracer) they select TRACING.
 # This allows those options to appear when no other tracer is selected. But the
@@ -159,18 +168,20 @@ config FUNCTION_GRAPH_TRACER
 	  the return value. This is done by setting the current return
 	  address on the current task structure into a stack of calls.
 
+config TRACE_PREEMPT_TOGGLE
+	bool
+	help
+	  Enables hooks which will be called when preemption is first disabled,
+	  and last enabled.
 
 config PREEMPTIRQ_EVENTS
 	bool "Enable trace events for preempt and irq disable/enable"
 	select TRACE_IRQFLAGS
-	depends on DEBUG_PREEMPT || !PROVE_LOCKING
-	depends on TRACING
+	select TRACE_PREEMPT_TOGGLE if PREEMPT
+	select GENERIC_TRACER
 	default n
 	help
 	  Enable tracing of disable and enable events for preemption and irqs.
-	  For tracing preempt disable/enable events, DEBUG_PREEMPT must be
-	  enabled. For tracing irq disable/enable events, PROVE_LOCKING must
-	  be disabled.
 
 config IRQSOFF_TRACER
 	bool "Interrupts-off Latency Tracer"
@@ -207,6 +218,7 @@ config PREEMPT_TRACER
 	select RING_BUFFER_ALLOW_SWAP
 	select TRACER_SNAPSHOT
 	select TRACER_SNAPSHOT_PER_CPU_SWAP
+	select TRACE_PREEMPT_TOGGLE
 	help
 	  This option measures the time spent in preemption-off critical
 	  sections, with microsecond accuracy.
diff --git a/kernel/trace/Makefile b/kernel/trace/Makefile
index e2538c7638d4..84a0cb222f20 100644
--- a/kernel/trace/Makefile
+++ b/kernel/trace/Makefile
@@ -35,7 +35,7 @@ obj-$(CONFIG_TRACING) += trace_printk.o
 obj-$(CONFIG_TRACING_MAP) += tracing_map.o
 obj-$(CONFIG_CONTEXT_SWITCH_TRACER) += trace_sched_switch.o
 obj-$(CONFIG_FUNCTION_TRACER) += trace_functions.o
-obj-$(CONFIG_PREEMPTIRQ_EVENTS) += trace_irqsoff.o
+obj-$(CONFIG_PREEMPTIRQ_TRACEPOINTS) += trace_preemptirq.o
 obj-$(CONFIG_IRQSOFF_TRACER) += trace_irqsoff.o
 obj-$(CONFIG_PREEMPT_TRACER) += trace_irqsoff.o
 obj-$(CONFIG_SCHED_TRACER) += trace_sched_wakeup.o
diff --git a/kernel/trace/trace_irqsoff.c b/kernel/trace/trace_irqsoff.c
index f8daa754cce2..d2d8284088f0 100644
--- a/kernel/trace/trace_irqsoff.c
+++ b/kernel/trace/trace_irqsoff.c
@@ -16,7 +16,6 @@
 
 #include "trace.h"
 
-#define CREATE_TRACE_POINTS
 #include <trace/events/preemptirq.h>
 
 #if defined(CONFIG_IRQSOFF_TRACER) || defined(CONFIG_PREEMPT_TRACER)
@@ -450,66 +449,6 @@ void stop_critical_timings(void)
 }
 EXPORT_SYMBOL_GPL(stop_critical_timings);
 
-#ifdef CONFIG_IRQSOFF_TRACER
-#ifdef CONFIG_PROVE_LOCKING
-void time_hardirqs_on(unsigned long a0, unsigned long a1)
-{
-	if (!preempt_trace() && irq_trace())
-		stop_critical_timing(a0, a1);
-}
-
-void time_hardirqs_off(unsigned long a0, unsigned long a1)
-{
-	if (!preempt_trace() && irq_trace())
-		start_critical_timing(a0, a1);
-}
-
-#else /* !CONFIG_PROVE_LOCKING */
-
-/*
- * We are only interested in hardirq on/off events:
- */
-static inline void tracer_hardirqs_on(void)
-{
-	if (!preempt_trace() && irq_trace())
-		stop_critical_timing(CALLER_ADDR0, CALLER_ADDR1);
-}
-
-static inline void tracer_hardirqs_off(void)
-{
-	if (!preempt_trace() && irq_trace())
-		start_critical_timing(CALLER_ADDR0, CALLER_ADDR1);
-}
-
-static inline void tracer_hardirqs_on_caller(unsigned long caller_addr)
-{
-	if (!preempt_trace() && irq_trace())
-		stop_critical_timing(CALLER_ADDR0, caller_addr);
-}
-
-static inline void tracer_hardirqs_off_caller(unsigned long caller_addr)
-{
-	if (!preempt_trace() && irq_trace())
-		start_critical_timing(CALLER_ADDR0, caller_addr);
-}
-
-#endif /* CONFIG_PROVE_LOCKING */
-#endif /*  CONFIG_IRQSOFF_TRACER */
-
-#ifdef CONFIG_PREEMPT_TRACER
-static inline void tracer_preempt_on(unsigned long a0, unsigned long a1)
-{
-	if (preempt_trace() && !irq_trace())
-		stop_critical_timing(a0, a1);
-}
-
-static inline void tracer_preempt_off(unsigned long a0, unsigned long a1)
-{
-	if (preempt_trace() && !irq_trace())
-		start_critical_timing(a0, a1);
-}
-#endif /* CONFIG_PREEMPT_TRACER */
-
 #ifdef CONFIG_FUNCTION_TRACER
 static bool function_enabled;
 
@@ -659,15 +598,34 @@ static void irqsoff_tracer_stop(struct trace_array *tr)
 }
 
 #ifdef CONFIG_IRQSOFF_TRACER
+/*
+ * We are only interested in hardirq on/off events:
+ */
+static void tracer_hardirqs_on(void *none, unsigned long a0, unsigned long a1)
+{
+	if (!preempt_trace() && irq_trace())
+		stop_critical_timing(a0, a1);
+}
+
+static void tracer_hardirqs_off(void *none, unsigned long a0, unsigned long a1)
+{
+	if (!preempt_trace() && irq_trace())
+		start_critical_timing(a0, a1);
+}
+
 static int irqsoff_tracer_init(struct trace_array *tr)
 {
 	trace_type = TRACER_IRQS_OFF;
 
+	register_trace_irq_disable(tracer_hardirqs_off, NULL);
+	register_trace_irq_enable(tracer_hardirqs_on, NULL);
 	return __irqsoff_tracer_init(tr);
 }
 
 static void irqsoff_tracer_reset(struct trace_array *tr)
 {
+	unregister_trace_irq_disable(tracer_hardirqs_off, NULL);
+	unregister_trace_irq_enable(tracer_hardirqs_on, NULL);
 	__irqsoff_tracer_reset(tr);
 }
 
@@ -692,19 +650,37 @@ static struct tracer irqsoff_tracer __read_mostly =
 };
 # define register_irqsoff(trace) register_tracer(&trace)
 #else
+static inline void tracer_hardirqs_on(unsigned long a0, unsigned long a1) { }
+static inline void tracer_hardirqs_off(unsigned long a0, unsigned long a1) { }
 # define register_irqsoff(trace) do { } while (0)
-#endif
+#endif /*  CONFIG_IRQSOFF_TRACER */
 
 #ifdef CONFIG_PREEMPT_TRACER
+static void tracer_preempt_on(void *none, unsigned long a0, unsigned long a1)
+{
+	if (preempt_trace() && !irq_trace())
+		stop_critical_timing(a0, a1);
+}
+
+static void tracer_preempt_off(void *none, unsigned long a0, unsigned long a1)
+{
+	if (preempt_trace() && !irq_trace())
+		start_critical_timing(a0, a1);
+}
+
 static int preemptoff_tracer_init(struct trace_array *tr)
 {
 	trace_type = TRACER_PREEMPT_OFF;
 
+	register_trace_preempt_disable(tracer_preempt_off, NULL);
+	register_trace_preempt_enable(tracer_preempt_on, NULL);
 	return __irqsoff_tracer_init(tr);
 }
 
 static void preemptoff_tracer_reset(struct trace_array *tr)
 {
+	unregister_trace_preempt_disable(tracer_preempt_off, NULL);
+	unregister_trace_preempt_enable(tracer_preempt_on, NULL);
 	__irqsoff_tracer_reset(tr);
 }
 
@@ -729,21 +705,32 @@ static struct tracer preemptoff_tracer __read_mostly =
 };
 # define register_preemptoff(trace) register_tracer(&trace)
 #else
+static inline void tracer_preempt_on(unsigned long a0, unsigned long a1) { }
+static inline void tracer_preempt_off(unsigned long a0, unsigned long a1) { }
 # define register_preemptoff(trace) do { } while (0)
-#endif
+#endif /* CONFIG_PREEMPT_TRACER */
 
-#if defined(CONFIG_IRQSOFF_TRACER) && \
-	defined(CONFIG_PREEMPT_TRACER)
+#if defined(CONFIG_IRQSOFF_TRACER) && defined(CONFIG_PREEMPT_TRACER)
 
 static int preemptirqsoff_tracer_init(struct trace_array *tr)
 {
 	trace_type = TRACER_IRQS_OFF | TRACER_PREEMPT_OFF;
 
+	register_trace_irq_disable(tracer_hardirqs_off, NULL);
+	register_trace_irq_enable(tracer_hardirqs_on, NULL);
+	register_trace_preempt_disable(tracer_preempt_off, NULL);
+	register_trace_preempt_enable(tracer_preempt_on, NULL);
+
 	return __irqsoff_tracer_init(tr);
 }
 
 static void preemptirqsoff_tracer_reset(struct trace_array *tr)
 {
+	unregister_trace_irq_disable(tracer_hardirqs_off, NULL);
+	unregister_trace_irq_enable(tracer_hardirqs_on, NULL);
+	unregister_trace_preempt_disable(tracer_preempt_off, NULL);
+	unregister_trace_preempt_enable(tracer_preempt_on, NULL);
+
 	__irqsoff_tracer_reset(tr);
 }
 
@@ -782,99 +769,3 @@ __init static int init_irqsoff_tracer(void)
 }
 core_initcall(init_irqsoff_tracer);
 #endif /* IRQSOFF_TRACER || PREEMPTOFF_TRACER */
-
-#ifndef CONFIG_IRQSOFF_TRACER
-static inline void tracer_hardirqs_on(void) { }
-static inline void tracer_hardirqs_off(void) { }
-static inline void tracer_hardirqs_on_caller(unsigned long caller_addr) { }
-static inline void tracer_hardirqs_off_caller(unsigned long caller_addr) { }
-#endif
-
-#ifndef CONFIG_PREEMPT_TRACER
-static inline void tracer_preempt_on(unsigned long a0, unsigned long a1) { }
-static inline void tracer_preempt_off(unsigned long a0, unsigned long a1) { }
-#endif
-
-#if defined(CONFIG_TRACE_IRQFLAGS) && !defined(CONFIG_PROVE_LOCKING)
-/* Per-cpu variable to prevent redundant calls when IRQs already off */
-static DEFINE_PER_CPU(int, tracing_irq_cpu);
-
-void trace_hardirqs_on(void)
-{
-	if (!this_cpu_read(tracing_irq_cpu))
-		return;
-
-	trace_irq_enable_rcuidle(CALLER_ADDR0, CALLER_ADDR1);
-	tracer_hardirqs_on();
-
-	this_cpu_write(tracing_irq_cpu, 0);
-}
-EXPORT_SYMBOL(trace_hardirqs_on);
-
-void trace_hardirqs_off(void)
-{
-	if (this_cpu_read(tracing_irq_cpu))
-		return;
-
-	this_cpu_write(tracing_irq_cpu, 1);
-
-	trace_irq_disable_rcuidle(CALLER_ADDR0, CALLER_ADDR1);
-	tracer_hardirqs_off();
-}
-EXPORT_SYMBOL(trace_hardirqs_off);
-
-__visible void trace_hardirqs_on_caller(unsigned long caller_addr)
-{
-	if (!this_cpu_read(tracing_irq_cpu))
-		return;
-
-	trace_irq_enable_rcuidle(CALLER_ADDR0, caller_addr);
-	tracer_hardirqs_on_caller(caller_addr);
-
-	this_cpu_write(tracing_irq_cpu, 0);
-}
-EXPORT_SYMBOL(trace_hardirqs_on_caller);
-
-__visible void trace_hardirqs_off_caller(unsigned long caller_addr)
-{
-	if (this_cpu_read(tracing_irq_cpu))
-		return;
-
-	this_cpu_write(tracing_irq_cpu, 1);
-
-	trace_irq_disable_rcuidle(CALLER_ADDR0, caller_addr);
-	tracer_hardirqs_off_caller(caller_addr);
-}
-EXPORT_SYMBOL(trace_hardirqs_off_caller);
-
-/*
- * Stubs:
- */
-
-void trace_softirqs_on(unsigned long ip)
-{
-}
-
-void trace_softirqs_off(unsigned long ip)
-{
-}
-
-inline void print_irqtrace_events(struct task_struct *curr)
-{
-}
-#endif
-
-#if defined(CONFIG_PREEMPT_TRACER) || \
-	(defined(CONFIG_DEBUG_PREEMPT) && defined(CONFIG_PREEMPTIRQ_EVENTS))
-void trace_preempt_on(unsigned long a0, unsigned long a1)
-{
-	trace_preempt_enable_rcuidle(a0, a1);
-	tracer_preempt_on(a0, a1);
-}
-
-void trace_preempt_off(unsigned long a0, unsigned long a1)
-{
-	trace_preempt_disable_rcuidle(a0, a1);
-	tracer_preempt_off(a0, a1);
-}
-#endif
diff --git a/kernel/trace/trace_preemptirq.c b/kernel/trace/trace_preemptirq.c
new file mode 100644
index 000000000000..dc01c7f4d326
--- /dev/null
+++ b/kernel/trace/trace_preemptirq.c
@@ -0,0 +1,71 @@
+/*
+ * preemptoff and irqoff tracepoints
+ *
+ * Copyright (C) Joel Fernandes (Google) <joel@joelfernandes.org>
+ */
+
+#include <linux/kallsyms.h>
+#include <linux/uaccess.h>
+#include <linux/module.h>
+#include <linux/ftrace.h>
+
+#define CREATE_TRACE_POINTS
+#include <trace/events/preemptirq.h>
+
+#ifdef CONFIG_TRACE_IRQFLAGS
+/* Per-cpu variable to prevent redundant calls when IRQs already off */
+static DEFINE_PER_CPU(int, tracing_irq_cpu);
+
+void trace_hardirqs_on(void)
+{
+	if (lockdep_recursing(current) || !this_cpu_read(tracing_irq_cpu))
+		return;
+
+	trace_irq_enable_rcuidle(CALLER_ADDR0, CALLER_ADDR1);
+	this_cpu_write(tracing_irq_cpu, 0);
+}
+EXPORT_SYMBOL(trace_hardirqs_on);
+
+void trace_hardirqs_off(void)
+{
+	if (lockdep_recursing(current) || this_cpu_read(tracing_irq_cpu))
+		return;
+
+	this_cpu_write(tracing_irq_cpu, 1);
+	trace_irq_disable_rcuidle(CALLER_ADDR0, CALLER_ADDR1);
+}
+EXPORT_SYMBOL(trace_hardirqs_off);
+
+__visible void trace_hardirqs_on_caller(unsigned long caller_addr)
+{
+	if (lockdep_recursing(current) || !this_cpu_read(tracing_irq_cpu))
+		return;
+
+	trace_irq_enable_rcuidle(CALLER_ADDR0, caller_addr);
+	this_cpu_write(tracing_irq_cpu, 0);
+}
+EXPORT_SYMBOL(trace_hardirqs_on_caller);
+
+__visible void trace_hardirqs_off_caller(unsigned long caller_addr)
+{
+	if (lockdep_recursing(current) || this_cpu_read(tracing_irq_cpu))
+		return;
+
+	this_cpu_write(tracing_irq_cpu, 1);
+	trace_irq_disable_rcuidle(CALLER_ADDR0, caller_addr);
+}
+EXPORT_SYMBOL(trace_hardirqs_off_caller);
+#endif /* CONFIG_TRACE_IRQFLAGS */
+
+#ifdef CONFIG_TRACE_PREEMPT_TOGGLE
+
+void trace_preempt_on(unsigned long a0, unsigned long a1)
+{
+	trace_preempt_enable_rcuidle(a0, a1);
+}
+
+void trace_preempt_off(unsigned long a0, unsigned long a1)
+{
+	trace_preempt_disable_rcuidle(a0, a1);
+}
+#endif
-- 
2.17.0.441.gb46fe60e1d-goog

^ permalink raw reply	[flat|nested] 33+ messages in thread

* [PATCH v7 6/8] tracing: Centralize preemptirq tracepoints and unify their usage
@ 2018-05-24  1:21   ` joelaf
  0 siblings, 0 replies; 33+ messages in thread
From: joelaf @ 2018-05-24  1:21 UTC (permalink / raw)


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

This patch detaches the preemptirq tracepoints from the tracers and
keeps it separate.

Advantages:
* Lockdep and irqsoff event can now run in parallel since they no longer
have their own calls.

* This unifies the usecase of adding hooks to an irqsoff and irqson
event, and a preemptoff and preempton event.
  3 users of the events exist:
  - Lockdep
  - irqsoff and preemptoff tracers
  - irqs and preempt trace events

The unification cleans up several ifdefs and makes the code in preempt
tracer and irqsoff tracers simpler. It gets rid of all the horrific
ifdeferry around PROVE_LOCKING and makes configuration of the different
users of the tracepoints more easy and understandable. It also gets rid
of the time_* function calls from the lockdep hooks used to call into
the preemptirq tracer which is not needed anymore. The negative delta in
lines of code in this patch is quite large too.

In the patch we introduce a new CONFIG option PREEMPTIRQ_TRACEPOINTS
as a single point for registering probes onto the tracepoints. With
this,
the web of config options for preempt/irq toggle tracepoints and its
users becomes:

 PREEMPT_TRACER   PREEMPTIRQ_EVENTS  IRQSOFF_TRACER PROVE_LOCKING
       |                 |     \         |           |
       \    (selects)    /      \        \ (selects) /
      TRACE_PREEMPT_TOGGLE       ----> TRACE_IRQFLAGS
                      \                  /
                       \ (depends on)   /
                     PREEMPTIRQ_TRACEPOINTS

One note, I have to check for lockdep recursion in the code that calls
the trace events API and bail out if we're in lockdep recursion
protection to prevent something like the following case: a spin_lock is
taken. Then lockdep_acquired is called.  That does a raw_local_irq_save
and then sets lockdep_recursion, and then calls __lockdep_acquired. In
this function, a call to get_lock_stats happens which calls
preempt_disable, which calls trace IRQS off somewhere which enters my
tracepoint code and sets the tracing_irq_cpu flag to prevent recursion.
This flag is then never cleared causing lockdep paths to never be
entered and thus causing splats and other bad things.

Other than the performance tests mentioned in the previous patch, I also
ran the locking API test suite. I verified that all tests cases are
passing.

I also injected issues by not registering lockdep probes onto the
tracepoints and I see failures to confirm that the probes are indeed
working.

Without probes:

[    0.000000]      hard-irqs-on + irq-safe-A/21:  ok  |  ok  |  ok  |
[    0.000000]      soft-irqs-on + irq-safe-A/21:  ok  |  ok  |  ok  |
[    0.000000]        sirq-safe-A => hirqs-on/12:  ok  |  ok  |  ok  |
[    0.000000]        sirq-safe-A => hirqs-on/21:  ok  |  ok  |  ok  |
[    0.000000]          hard-safe-A + irqs-on/12:  ok  |  ok  |  ok  |
[    0.000000]          soft-safe-A + irqs-on/12:  ok  |  ok  |  ok  |
[    0.000000]          hard-safe-A + irqs-on/21:  ok  |  ok  |  ok  |
[    0.000000]          soft-safe-A + irqs-on/21:  ok  |  ok  |  ok  |
[    0.000000]     hard-safe-A + unsafe-B #1/123:  ok  |  ok  |  ok  |
[    0.000000]     soft-safe-A + unsafe-B #1/123:  ok  |  ok  |  ok  |

With probes:

[    0.000000]      hard-irqs-on + irq-safe-A/21:  ok  |  ok  |  ok  |
[    0.000000]      soft-irqs-on + irq-safe-A/21:  ok  |  ok  |  ok  |
[    0.000000]        sirq-safe-A => hirqs-on/12:FAILED|FAILED|  ok  |
[    0.000000]        sirq-safe-A => hirqs-on/21:FAILED|FAILED|  ok  |
[    0.000000]          hard-safe-A + irqs-on/12:FAILED|FAILED|  ok  |
[    0.000000]          soft-safe-A + irqs-on/12:FAILED|FAILED|  ok  |
[    0.000000]          hard-safe-A + irqs-on/21:FAILED|FAILED|  ok  |
[    0.000000]          soft-safe-A + irqs-on/21:FAILED|FAILED|  ok  |
[    0.000000]     hard-safe-A + unsafe-B #1/123:  ok  |  ok  |  ok  |
[    0.000000]     soft-safe-A + unsafe-B #1/123:  ok  |  ok  |  ok  |

Signed-off-by: Joel Fernandes (Google) <joel at joelfernandes.org>
---
 include/linux/ftrace.h            |  11 +-
 include/linux/irqflags.h          |  11 +-
 include/linux/lockdep.h           |   8 +-
 include/linux/preempt.h           |   2 +-
 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      | 213 ++++++++----------------------
 kernel/trace/trace_preemptirq.c   |  71 ++++++++++
 12 files changed, 189 insertions(+), 216 deletions(-)
 create mode 100644 kernel/trace/trace_preemptirq.c

diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
index 9c3c9a319e48..5191030af0c0 100644
--- a/include/linux/ftrace.h
+++ b/include/linux/ftrace.h
@@ -709,16 +709,7 @@ static inline unsigned long get_lock_parent_ip(void)
 	return CALLER_ADDR2;
 }
 
-#ifdef CONFIG_IRQSOFF_TRACER
-  extern void time_hardirqs_on(unsigned long a0, unsigned long a1);
-  extern void time_hardirqs_off(unsigned long a0, unsigned long a1);
-#else
-  static inline void time_hardirqs_on(unsigned long a0, unsigned long a1) { }
-  static inline void time_hardirqs_off(unsigned long a0, unsigned long a1) { }
-#endif
-
-#if defined(CONFIG_PREEMPT_TRACER) || \
-	(defined(CONFIG_DEBUG_PREEMPT) && defined(CONFIG_PREEMPTIRQ_EVENTS))
+#ifdef CONFIG_TRACE_PREEMPT_TOGGLE
   extern void trace_preempt_on(unsigned long a0, unsigned long a1);
   extern void trace_preempt_off(unsigned long a0, unsigned long a1);
 #else
diff --git a/include/linux/irqflags.h b/include/linux/irqflags.h
index 9700f00bbc04..50edb9cbbd26 100644
--- a/include/linux/irqflags.h
+++ b/include/linux/irqflags.h
@@ -15,9 +15,16 @@
 #include <linux/typecheck.h>
 #include <asm/irqflags.h>
 
-#ifdef CONFIG_TRACE_IRQFLAGS
+/* Currently trace_softirqs_on/off is used only by lockdep */
+#ifdef CONFIG_PROVE_LOCKING
   extern void trace_softirqs_on(unsigned long ip);
   extern void trace_softirqs_off(unsigned long ip);
+#else
+# define trace_softirqs_on(ip)	do { } while (0)
+# define trace_softirqs_off(ip)	do { } while (0)
+#endif
+
+#ifdef CONFIG_TRACE_IRQFLAGS
   extern void trace_hardirqs_on(void);
   extern void trace_hardirqs_off(void);
 # define trace_hardirq_context(p)	((p)->hardirq_context)
@@ -43,8 +50,6 @@ do {						\
 #else
 # define trace_hardirqs_on()		do { } while (0)
 # define trace_hardirqs_off()		do { } while (0)
-# define trace_softirqs_on(ip)		do { } while (0)
-# define trace_softirqs_off(ip)		do { } while (0)
 # define trace_hardirq_context(p)	0
 # define trace_softirq_context(p)	0
 # define trace_hardirqs_enabled(p)	0
diff --git a/include/linux/lockdep.h b/include/linux/lockdep.h
index 6fc77d4dbdcd..a8113357ceeb 100644
--- a/include/linux/lockdep.h
+++ b/include/linux/lockdep.h
@@ -266,7 +266,8 @@ struct held_lock {
 /*
  * Initialization, self-test and debugging-output methods:
  */
-extern void lockdep_info(void);
+extern void lockdep_init(void);
+extern void lockdep_init_early(void);
 extern void lockdep_reset(void);
 extern void lockdep_reset_lock(struct lockdep_map *lock);
 extern void lockdep_free_key_range(void *start, unsigned long size);
@@ -406,7 +407,8 @@ static inline void lockdep_on(void)
 # define lock_downgrade(l, i)			do { } while (0)
 # define lock_set_class(l, n, k, s, i)		do { } while (0)
 # define lock_set_subclass(l, s, i)		do { } while (0)
-# define lockdep_info()				do { } while (0)
+# define lockdep_init()				do { } while (0)
+# define lockdep_init_early()			do { } while (0)
 # define lockdep_init_map(lock, name, key, sub) \
 		do { (void)(name); (void)(key); } while (0)
 # define lockdep_set_class(lock, key)		do { (void)(key); } while (0)
@@ -532,7 +534,7 @@ do {								\
 
 #endif /* CONFIG_LOCKDEP */
 
-#ifdef CONFIG_TRACE_IRQFLAGS
+#ifdef CONFIG_PROVE_LOCKING
 extern void print_irqtrace_events(struct task_struct *curr);
 #else
 static inline void print_irqtrace_events(struct task_struct *curr)
diff --git a/include/linux/preempt.h b/include/linux/preempt.h
index 5bd3f151da78..c01813c3fbe9 100644
--- a/include/linux/preempt.h
+++ b/include/linux/preempt.h
@@ -150,7 +150,7 @@
  */
 #define in_atomic_preempt_off() (preempt_count() != PREEMPT_DISABLE_OFFSET)
 
-#if defined(CONFIG_DEBUG_PREEMPT) || defined(CONFIG_PREEMPT_TRACER)
+#if defined(CONFIG_DEBUG_PREEMPT) || defined(CONFIG_TRACE_PREEMPT_TOGGLE)
 extern void preempt_count_add(int val);
 extern void preempt_count_sub(int val);
 #define preempt_count_dec_and_test() \
diff --git a/include/trace/events/preemptirq.h b/include/trace/events/preemptirq.h
index 9c4eb33c5a1d..9a0d4ceeb166 100644
--- a/include/trace/events/preemptirq.h
+++ b/include/trace/events/preemptirq.h
@@ -1,4 +1,4 @@
-#ifdef CONFIG_PREEMPTIRQ_EVENTS
+#ifdef CONFIG_PREEMPTIRQ_TRACEPOINTS
 
 #undef TRACE_SYSTEM
 #define TRACE_SYSTEM preemptirq
@@ -32,7 +32,7 @@ DECLARE_EVENT_CLASS(preemptirq_template,
 		  (void *)((unsigned long)(_stext) + __entry->parent_offs))
 );
 
-#ifndef CONFIG_PROVE_LOCKING
+#ifdef CONFIG_TRACE_IRQFLAGS
 DEFINE_EVENT(preemptirq_template, irq_disable,
 	     TP_PROTO(unsigned long ip, unsigned long parent_ip),
 	     TP_ARGS(ip, parent_ip));
@@ -40,9 +40,14 @@ DEFINE_EVENT(preemptirq_template, irq_disable,
 DEFINE_EVENT(preemptirq_template, irq_enable,
 	     TP_PROTO(unsigned long ip, unsigned long parent_ip),
 	     TP_ARGS(ip, parent_ip));
+#else
+#define trace_irq_enable(...)
+#define trace_irq_disable(...)
+#define trace_irq_enable_rcuidle(...)
+#define trace_irq_disable_rcuidle(...)
 #endif
 
-#ifdef CONFIG_DEBUG_PREEMPT
+#ifdef CONFIG_TRACE_PREEMPT_TOGGLE
 DEFINE_EVENT(preemptirq_template, preempt_disable,
 	     TP_PROTO(unsigned long ip, unsigned long parent_ip),
 	     TP_ARGS(ip, parent_ip));
@@ -50,22 +55,22 @@ DEFINE_EVENT(preemptirq_template, preempt_disable,
 DEFINE_EVENT(preemptirq_template, preempt_enable,
 	     TP_PROTO(unsigned long ip, unsigned long parent_ip),
 	     TP_ARGS(ip, parent_ip));
+#else
+#define trace_preempt_enable(...)
+#define trace_preempt_disable(...)
+#define trace_preempt_enable_rcuidle(...)
+#define trace_preempt_disable_rcuidle(...)
 #endif
 
 #endif /* _TRACE_PREEMPTIRQ_H */
 
 #include <trace/define_trace.h>
 
-#endif /* !CONFIG_PREEMPTIRQ_EVENTS */
-
-#if !defined(CONFIG_PREEMPTIRQ_EVENTS) || defined(CONFIG_PROVE_LOCKING)
+#else /* !CONFIG_PREEMPTIRQ_TRACEPOINTS */
 #define trace_irq_enable(...)
 #define trace_irq_disable(...)
 #define trace_irq_enable_rcuidle(...)
 #define trace_irq_disable_rcuidle(...)
-#endif
-
-#if !defined(CONFIG_PREEMPTIRQ_EVENTS) || !defined(CONFIG_DEBUG_PREEMPT)
 #define trace_preempt_enable(...)
 #define trace_preempt_disable(...)
 #define trace_preempt_enable_rcuidle(...)
diff --git a/init/main.c b/init/main.c
index fd37315835b4..5181c5bc2f0c 100644
--- a/init/main.c
+++ b/init/main.c
@@ -647,6 +647,9 @@ asmlinkage __visible void __init start_kernel(void)
 	profile_init();
 	call_function_init();
 	WARN(!irqs_disabled(), "Interrupts were enabled early\n");
+
+	lockdep_init_early();
+
 	early_boot_irqs_disabled = false;
 	local_irq_enable();
 
@@ -662,7 +665,7 @@ asmlinkage __visible void __init start_kernel(void)
 		panic("Too many boot %s vars at `%s'", panic_later,
 		      panic_param);
 
-	lockdep_info();
+	lockdep_init();
 
 	/*
 	 * Need to run this when irqs are enabled, because it wants
diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index 023386338269..871a42232858 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -55,6 +55,7 @@
 
 #include "lockdep_internals.h"
 
+#include <trace/events/preemptirq.h>
 #define CREATE_TRACE_POINTS
 #include <trace/events/lock.h>
 
@@ -2841,10 +2842,9 @@ static void __trace_hardirqs_on_caller(unsigned long ip)
 	debug_atomic_inc(hardirqs_on_events);
 }
 
-__visible void trace_hardirqs_on_caller(unsigned long ip)
+static void lockdep_hardirqs_on(void *none, unsigned long ignore,
+				unsigned long ip)
 {
-	time_hardirqs_on(CALLER_ADDR0, ip);
-
 	if (unlikely(!debug_locks || current->lockdep_recursion))
 		return;
 
@@ -2883,23 +2883,15 @@ __visible void trace_hardirqs_on_caller(unsigned long ip)
 	__trace_hardirqs_on_caller(ip);
 	current->lockdep_recursion = 0;
 }
-EXPORT_SYMBOL(trace_hardirqs_on_caller);
-
-void trace_hardirqs_on(void)
-{
-	trace_hardirqs_on_caller(CALLER_ADDR0);
-}
-EXPORT_SYMBOL(trace_hardirqs_on);
 
 /*
  * Hardirqs were disabled:
  */
-__visible void trace_hardirqs_off_caller(unsigned long ip)
+static void lockdep_hardirqs_off(void *none, unsigned long ignore,
+				 unsigned long ip)
 {
 	struct task_struct *curr = current;
 
-	time_hardirqs_off(CALLER_ADDR0, ip);
-
 	if (unlikely(!debug_locks || current->lockdep_recursion))
 		return;
 
@@ -2921,13 +2913,6 @@ __visible void trace_hardirqs_off_caller(unsigned long ip)
 	} else
 		debug_atomic_inc(redundant_hardirqs_off);
 }
-EXPORT_SYMBOL(trace_hardirqs_off_caller);
-
-void trace_hardirqs_off(void)
-{
-	trace_hardirqs_off_caller(CALLER_ADDR0);
-}
-EXPORT_SYMBOL(trace_hardirqs_off);
 
 /*
  * Softirqs will be enabled:
@@ -4334,7 +4319,15 @@ void lockdep_reset_lock(struct lockdep_map *lock)
 	raw_local_irq_restore(flags);
 }
 
-void __init lockdep_info(void)
+void __init lockdep_init_early(void)
+{
+#ifdef CONFIG_PROVE_LOCKING
+	register_trace_prio_irq_disable(lockdep_hardirqs_off, NULL, INT_MAX);
+	register_trace_prio_irq_enable(lockdep_hardirqs_on, NULL, INT_MIN);
+#endif
+}
+
+void __init lockdep_init(void)
 {
 	printk("Lock dependency validator: Copyright (c) 2006 Red Hat, Inc., Ingo Molnar\n");
 
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 092f7c4de903..4e9c2d254fba 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -3189,7 +3189,7 @@ static inline void sched_tick_stop(int cpu) { }
 #endif
 
 #if defined(CONFIG_PREEMPT) && (defined(CONFIG_DEBUG_PREEMPT) || \
-				defined(CONFIG_PREEMPT_TRACER))
+				defined(CONFIG_TRACE_PREEMPT_TOGGLE))
 /*
  * If the value passed in is equal to the current preempt count
  * then we just disabled preemption. Start timing the latency.
diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig
index c4f0f2e4126e..0bcba2a76ad9 100644
--- a/kernel/trace/Kconfig
+++ b/kernel/trace/Kconfig
@@ -82,6 +82,15 @@ config RING_BUFFER_ALLOW_SWAP
 	 Allow the use of ring_buffer_swap_cpu.
 	 Adds a very slight overhead to tracing when enabled.
 
+config PREEMPTIRQ_TRACEPOINTS
+	bool
+	depends on TRACE_PREEMPT_TOGGLE || TRACE_IRQFLAGS
+	select TRACING
+	default y
+	help
+	  Create preempt/irq toggle tracepoints if needed, so that other parts
+	  of the kernel can use them to generate or add hooks to them.
+
 # All tracer options should select GENERIC_TRACER. For those options that are
 # enabled by all tracers (context switch and event tracer) they select TRACING.
 # This allows those options to appear when no other tracer is selected. But the
@@ -159,18 +168,20 @@ config FUNCTION_GRAPH_TRACER
 	  the return value. This is done by setting the current return
 	  address on the current task structure into a stack of calls.
 
+config TRACE_PREEMPT_TOGGLE
+	bool
+	help
+	  Enables hooks which will be called when preemption is first disabled,
+	  and last enabled.
 
 config PREEMPTIRQ_EVENTS
 	bool "Enable trace events for preempt and irq disable/enable"
 	select TRACE_IRQFLAGS
-	depends on DEBUG_PREEMPT || !PROVE_LOCKING
-	depends on TRACING
+	select TRACE_PREEMPT_TOGGLE if PREEMPT
+	select GENERIC_TRACER
 	default n
 	help
 	  Enable tracing of disable and enable events for preemption and irqs.
-	  For tracing preempt disable/enable events, DEBUG_PREEMPT must be
-	  enabled. For tracing irq disable/enable events, PROVE_LOCKING must
-	  be disabled.
 
 config IRQSOFF_TRACER
 	bool "Interrupts-off Latency Tracer"
@@ -207,6 +218,7 @@ config PREEMPT_TRACER
 	select RING_BUFFER_ALLOW_SWAP
 	select TRACER_SNAPSHOT
 	select TRACER_SNAPSHOT_PER_CPU_SWAP
+	select TRACE_PREEMPT_TOGGLE
 	help
 	  This option measures the time spent in preemption-off critical
 	  sections, with microsecond accuracy.
diff --git a/kernel/trace/Makefile b/kernel/trace/Makefile
index e2538c7638d4..84a0cb222f20 100644
--- a/kernel/trace/Makefile
+++ b/kernel/trace/Makefile
@@ -35,7 +35,7 @@ obj-$(CONFIG_TRACING) += trace_printk.o
 obj-$(CONFIG_TRACING_MAP) += tracing_map.o
 obj-$(CONFIG_CONTEXT_SWITCH_TRACER) += trace_sched_switch.o
 obj-$(CONFIG_FUNCTION_TRACER) += trace_functions.o
-obj-$(CONFIG_PREEMPTIRQ_EVENTS) += trace_irqsoff.o
+obj-$(CONFIG_PREEMPTIRQ_TRACEPOINTS) += trace_preemptirq.o
 obj-$(CONFIG_IRQSOFF_TRACER) += trace_irqsoff.o
 obj-$(CONFIG_PREEMPT_TRACER) += trace_irqsoff.o
 obj-$(CONFIG_SCHED_TRACER) += trace_sched_wakeup.o
diff --git a/kernel/trace/trace_irqsoff.c b/kernel/trace/trace_irqsoff.c
index f8daa754cce2..d2d8284088f0 100644
--- a/kernel/trace/trace_irqsoff.c
+++ b/kernel/trace/trace_irqsoff.c
@@ -16,7 +16,6 @@
 
 #include "trace.h"
 
-#define CREATE_TRACE_POINTS
 #include <trace/events/preemptirq.h>
 
 #if defined(CONFIG_IRQSOFF_TRACER) || defined(CONFIG_PREEMPT_TRACER)
@@ -450,66 +449,6 @@ void stop_critical_timings(void)
 }
 EXPORT_SYMBOL_GPL(stop_critical_timings);
 
-#ifdef CONFIG_IRQSOFF_TRACER
-#ifdef CONFIG_PROVE_LOCKING
-void time_hardirqs_on(unsigned long a0, unsigned long a1)
-{
-	if (!preempt_trace() && irq_trace())
-		stop_critical_timing(a0, a1);
-}
-
-void time_hardirqs_off(unsigned long a0, unsigned long a1)
-{
-	if (!preempt_trace() && irq_trace())
-		start_critical_timing(a0, a1);
-}
-
-#else /* !CONFIG_PROVE_LOCKING */
-
-/*
- * We are only interested in hardirq on/off events:
- */
-static inline void tracer_hardirqs_on(void)
-{
-	if (!preempt_trace() && irq_trace())
-		stop_critical_timing(CALLER_ADDR0, CALLER_ADDR1);
-}
-
-static inline void tracer_hardirqs_off(void)
-{
-	if (!preempt_trace() && irq_trace())
-		start_critical_timing(CALLER_ADDR0, CALLER_ADDR1);
-}
-
-static inline void tracer_hardirqs_on_caller(unsigned long caller_addr)
-{
-	if (!preempt_trace() && irq_trace())
-		stop_critical_timing(CALLER_ADDR0, caller_addr);
-}
-
-static inline void tracer_hardirqs_off_caller(unsigned long caller_addr)
-{
-	if (!preempt_trace() && irq_trace())
-		start_critical_timing(CALLER_ADDR0, caller_addr);
-}
-
-#endif /* CONFIG_PROVE_LOCKING */
-#endif /*  CONFIG_IRQSOFF_TRACER */
-
-#ifdef CONFIG_PREEMPT_TRACER
-static inline void tracer_preempt_on(unsigned long a0, unsigned long a1)
-{
-	if (preempt_trace() && !irq_trace())
-		stop_critical_timing(a0, a1);
-}
-
-static inline void tracer_preempt_off(unsigned long a0, unsigned long a1)
-{
-	if (preempt_trace() && !irq_trace())
-		start_critical_timing(a0, a1);
-}
-#endif /* CONFIG_PREEMPT_TRACER */
-
 #ifdef CONFIG_FUNCTION_TRACER
 static bool function_enabled;
 
@@ -659,15 +598,34 @@ static void irqsoff_tracer_stop(struct trace_array *tr)
 }
 
 #ifdef CONFIG_IRQSOFF_TRACER
+/*
+ * We are only interested in hardirq on/off events:
+ */
+static void tracer_hardirqs_on(void *none, unsigned long a0, unsigned long a1)
+{
+	if (!preempt_trace() && irq_trace())
+		stop_critical_timing(a0, a1);
+}
+
+static void tracer_hardirqs_off(void *none, unsigned long a0, unsigned long a1)
+{
+	if (!preempt_trace() && irq_trace())
+		start_critical_timing(a0, a1);
+}
+
 static int irqsoff_tracer_init(struct trace_array *tr)
 {
 	trace_type = TRACER_IRQS_OFF;
 
+	register_trace_irq_disable(tracer_hardirqs_off, NULL);
+	register_trace_irq_enable(tracer_hardirqs_on, NULL);
 	return __irqsoff_tracer_init(tr);
 }
 
 static void irqsoff_tracer_reset(struct trace_array *tr)
 {
+	unregister_trace_irq_disable(tracer_hardirqs_off, NULL);
+	unregister_trace_irq_enable(tracer_hardirqs_on, NULL);
 	__irqsoff_tracer_reset(tr);
 }
 
@@ -692,19 +650,37 @@ static struct tracer irqsoff_tracer __read_mostly =
 };
 # define register_irqsoff(trace) register_tracer(&trace)
 #else
+static inline void tracer_hardirqs_on(unsigned long a0, unsigned long a1) { }
+static inline void tracer_hardirqs_off(unsigned long a0, unsigned long a1) { }
 # define register_irqsoff(trace) do { } while (0)
-#endif
+#endif /*  CONFIG_IRQSOFF_TRACER */
 
 #ifdef CONFIG_PREEMPT_TRACER
+static void tracer_preempt_on(void *none, unsigned long a0, unsigned long a1)
+{
+	if (preempt_trace() && !irq_trace())
+		stop_critical_timing(a0, a1);
+}
+
+static void tracer_preempt_off(void *none, unsigned long a0, unsigned long a1)
+{
+	if (preempt_trace() && !irq_trace())
+		start_critical_timing(a0, a1);
+}
+
 static int preemptoff_tracer_init(struct trace_array *tr)
 {
 	trace_type = TRACER_PREEMPT_OFF;
 
+	register_trace_preempt_disable(tracer_preempt_off, NULL);
+	register_trace_preempt_enable(tracer_preempt_on, NULL);
 	return __irqsoff_tracer_init(tr);
 }
 
 static void preemptoff_tracer_reset(struct trace_array *tr)
 {
+	unregister_trace_preempt_disable(tracer_preempt_off, NULL);
+	unregister_trace_preempt_enable(tracer_preempt_on, NULL);
 	__irqsoff_tracer_reset(tr);
 }
 
@@ -729,21 +705,32 @@ static struct tracer preemptoff_tracer __read_mostly =
 };
 # define register_preemptoff(trace) register_tracer(&trace)
 #else
+static inline void tracer_preempt_on(unsigned long a0, unsigned long a1) { }
+static inline void tracer_preempt_off(unsigned long a0, unsigned long a1) { }
 # define register_preemptoff(trace) do { } while (0)
-#endif
+#endif /* CONFIG_PREEMPT_TRACER */
 
-#if defined(CONFIG_IRQSOFF_TRACER) && \
-	defined(CONFIG_PREEMPT_TRACER)
+#if defined(CONFIG_IRQSOFF_TRACER) && defined(CONFIG_PREEMPT_TRACER)
 
 static int preemptirqsoff_tracer_init(struct trace_array *tr)
 {
 	trace_type = TRACER_IRQS_OFF | TRACER_PREEMPT_OFF;
 
+	register_trace_irq_disable(tracer_hardirqs_off, NULL);
+	register_trace_irq_enable(tracer_hardirqs_on, NULL);
+	register_trace_preempt_disable(tracer_preempt_off, NULL);
+	register_trace_preempt_enable(tracer_preempt_on, NULL);
+
 	return __irqsoff_tracer_init(tr);
 }
 
 static void preemptirqsoff_tracer_reset(struct trace_array *tr)
 {
+	unregister_trace_irq_disable(tracer_hardirqs_off, NULL);
+	unregister_trace_irq_enable(tracer_hardirqs_on, NULL);
+	unregister_trace_preempt_disable(tracer_preempt_off, NULL);
+	unregister_trace_preempt_enable(tracer_preempt_on, NULL);
+
 	__irqsoff_tracer_reset(tr);
 }
 
@@ -782,99 +769,3 @@ __init static int init_irqsoff_tracer(void)
 }
 core_initcall(init_irqsoff_tracer);
 #endif /* IRQSOFF_TRACER || PREEMPTOFF_TRACER */
-
-#ifndef CONFIG_IRQSOFF_TRACER
-static inline void tracer_hardirqs_on(void) { }
-static inline void tracer_hardirqs_off(void) { }
-static inline void tracer_hardirqs_on_caller(unsigned long caller_addr) { }
-static inline void tracer_hardirqs_off_caller(unsigned long caller_addr) { }
-#endif
-
-#ifndef CONFIG_PREEMPT_TRACER
-static inline void tracer_preempt_on(unsigned long a0, unsigned long a1) { }
-static inline void tracer_preempt_off(unsigned long a0, unsigned long a1) { }
-#endif
-
-#if defined(CONFIG_TRACE_IRQFLAGS) && !defined(CONFIG_PROVE_LOCKING)
-/* Per-cpu variable to prevent redundant calls when IRQs already off */
-static DEFINE_PER_CPU(int, tracing_irq_cpu);
-
-void trace_hardirqs_on(void)
-{
-	if (!this_cpu_read(tracing_irq_cpu))
-		return;
-
-	trace_irq_enable_rcuidle(CALLER_ADDR0, CALLER_ADDR1);
-	tracer_hardirqs_on();
-
-	this_cpu_write(tracing_irq_cpu, 0);
-}
-EXPORT_SYMBOL(trace_hardirqs_on);
-
-void trace_hardirqs_off(void)
-{
-	if (this_cpu_read(tracing_irq_cpu))
-		return;
-
-	this_cpu_write(tracing_irq_cpu, 1);
-
-	trace_irq_disable_rcuidle(CALLER_ADDR0, CALLER_ADDR1);
-	tracer_hardirqs_off();
-}
-EXPORT_SYMBOL(trace_hardirqs_off);
-
-__visible void trace_hardirqs_on_caller(unsigned long caller_addr)
-{
-	if (!this_cpu_read(tracing_irq_cpu))
-		return;
-
-	trace_irq_enable_rcuidle(CALLER_ADDR0, caller_addr);
-	tracer_hardirqs_on_caller(caller_addr);
-
-	this_cpu_write(tracing_irq_cpu, 0);
-}
-EXPORT_SYMBOL(trace_hardirqs_on_caller);
-
-__visible void trace_hardirqs_off_caller(unsigned long caller_addr)
-{
-	if (this_cpu_read(tracing_irq_cpu))
-		return;
-
-	this_cpu_write(tracing_irq_cpu, 1);
-
-	trace_irq_disable_rcuidle(CALLER_ADDR0, caller_addr);
-	tracer_hardirqs_off_caller(caller_addr);
-}
-EXPORT_SYMBOL(trace_hardirqs_off_caller);
-
-/*
- * Stubs:
- */
-
-void trace_softirqs_on(unsigned long ip)
-{
-}
-
-void trace_softirqs_off(unsigned long ip)
-{
-}
-
-inline void print_irqtrace_events(struct task_struct *curr)
-{
-}
-#endif
-
-#if defined(CONFIG_PREEMPT_TRACER) || \
-	(defined(CONFIG_DEBUG_PREEMPT) && defined(CONFIG_PREEMPTIRQ_EVENTS))
-void trace_preempt_on(unsigned long a0, unsigned long a1)
-{
-	trace_preempt_enable_rcuidle(a0, a1);
-	tracer_preempt_on(a0, a1);
-}
-
-void trace_preempt_off(unsigned long a0, unsigned long a1)
-{
-	trace_preempt_disable_rcuidle(a0, a1);
-	tracer_preempt_off(a0, a1);
-}
-#endif
diff --git a/kernel/trace/trace_preemptirq.c b/kernel/trace/trace_preemptirq.c
new file mode 100644
index 000000000000..dc01c7f4d326
--- /dev/null
+++ b/kernel/trace/trace_preemptirq.c
@@ -0,0 +1,71 @@
+/*
+ * preemptoff and irqoff tracepoints
+ *
+ * Copyright (C) Joel Fernandes (Google) <joel at joelfernandes.org>
+ */
+
+#include <linux/kallsyms.h>
+#include <linux/uaccess.h>
+#include <linux/module.h>
+#include <linux/ftrace.h>
+
+#define CREATE_TRACE_POINTS
+#include <trace/events/preemptirq.h>
+
+#ifdef CONFIG_TRACE_IRQFLAGS
+/* Per-cpu variable to prevent redundant calls when IRQs already off */
+static DEFINE_PER_CPU(int, tracing_irq_cpu);
+
+void trace_hardirqs_on(void)
+{
+	if (lockdep_recursing(current) || !this_cpu_read(tracing_irq_cpu))
+		return;
+
+	trace_irq_enable_rcuidle(CALLER_ADDR0, CALLER_ADDR1);
+	this_cpu_write(tracing_irq_cpu, 0);
+}
+EXPORT_SYMBOL(trace_hardirqs_on);
+
+void trace_hardirqs_off(void)
+{
+	if (lockdep_recursing(current) || this_cpu_read(tracing_irq_cpu))
+		return;
+
+	this_cpu_write(tracing_irq_cpu, 1);
+	trace_irq_disable_rcuidle(CALLER_ADDR0, CALLER_ADDR1);
+}
+EXPORT_SYMBOL(trace_hardirqs_off);
+
+__visible void trace_hardirqs_on_caller(unsigned long caller_addr)
+{
+	if (lockdep_recursing(current) || !this_cpu_read(tracing_irq_cpu))
+		return;
+
+	trace_irq_enable_rcuidle(CALLER_ADDR0, caller_addr);
+	this_cpu_write(tracing_irq_cpu, 0);
+}
+EXPORT_SYMBOL(trace_hardirqs_on_caller);
+
+__visible void trace_hardirqs_off_caller(unsigned long caller_addr)
+{
+	if (lockdep_recursing(current) || this_cpu_read(tracing_irq_cpu))
+		return;
+
+	this_cpu_write(tracing_irq_cpu, 1);
+	trace_irq_disable_rcuidle(CALLER_ADDR0, caller_addr);
+}
+EXPORT_SYMBOL(trace_hardirqs_off_caller);
+#endif /* CONFIG_TRACE_IRQFLAGS */
+
+#ifdef CONFIG_TRACE_PREEMPT_TOGGLE
+
+void trace_preempt_on(unsigned long a0, unsigned long a1)
+{
+	trace_preempt_enable_rcuidle(a0, a1);
+}
+
+void trace_preempt_off(unsigned long a0, unsigned long a1)
+{
+	trace_preempt_disable_rcuidle(a0, a1);
+}
+#endif
-- 
2.17.0.441.gb46fe60e1d-goog

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^ permalink raw reply	[flat|nested] 33+ messages in thread

* [PATCH v7 6/8] tracing: Centralize preemptirq tracepoints and unify their usage
@ 2018-05-24  1:21   ` joelaf
  0 siblings, 0 replies; 33+ messages in thread
From: Joel Fernandes @ 2018-05-24  1:21 UTC (permalink / raw)


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

This patch detaches the preemptirq tracepoints from the tracers and
keeps it separate.

Advantages:
* Lockdep and irqsoff event can now run in parallel since they no longer
have their own calls.

* This unifies the usecase of adding hooks to an irqsoff and irqson
event, and a preemptoff and preempton event.
  3 users of the events exist:
  - Lockdep
  - irqsoff and preemptoff tracers
  - irqs and preempt trace events

The unification cleans up several ifdefs and makes the code in preempt
tracer and irqsoff tracers simpler. It gets rid of all the horrific
ifdeferry around PROVE_LOCKING and makes configuration of the different
users of the tracepoints more easy and understandable. It also gets rid
of the time_* function calls from the lockdep hooks used to call into
the preemptirq tracer which is not needed anymore. The negative delta in
lines of code in this patch is quite large too.

In the patch we introduce a new CONFIG option PREEMPTIRQ_TRACEPOINTS
as a single point for registering probes onto the tracepoints. With
this,
the web of config options for preempt/irq toggle tracepoints and its
users becomes:

 PREEMPT_TRACER   PREEMPTIRQ_EVENTS  IRQSOFF_TRACER PROVE_LOCKING
       |                 |     \         |           |
       \    (selects)    /      \        \ (selects) /
      TRACE_PREEMPT_TOGGLE       ----> TRACE_IRQFLAGS
                      \                  /
                       \ (depends on)   /
                     PREEMPTIRQ_TRACEPOINTS

One note, I have to check for lockdep recursion in the code that calls
the trace events API and bail out if we're in lockdep recursion
protection to prevent something like the following case: a spin_lock is
taken. Then lockdep_acquired is called.  That does a raw_local_irq_save
and then sets lockdep_recursion, and then calls __lockdep_acquired. In
this function, a call to get_lock_stats happens which calls
preempt_disable, which calls trace IRQS off somewhere which enters my
tracepoint code and sets the tracing_irq_cpu flag to prevent recursion.
This flag is then never cleared causing lockdep paths to never be
entered and thus causing splats and other bad things.

Other than the performance tests mentioned in the previous patch, I also
ran the locking API test suite. I verified that all tests cases are
passing.

I also injected issues by not registering lockdep probes onto the
tracepoints and I see failures to confirm that the probes are indeed
working.

Without probes:

[    0.000000]      hard-irqs-on + irq-safe-A/21:  ok  |  ok  |  ok  |
[    0.000000]      soft-irqs-on + irq-safe-A/21:  ok  |  ok  |  ok  |
[    0.000000]        sirq-safe-A => hirqs-on/12:  ok  |  ok  |  ok  |
[    0.000000]        sirq-safe-A => hirqs-on/21:  ok  |  ok  |  ok  |
[    0.000000]          hard-safe-A + irqs-on/12:  ok  |  ok  |  ok  |
[    0.000000]          soft-safe-A + irqs-on/12:  ok  |  ok  |  ok  |
[    0.000000]          hard-safe-A + irqs-on/21:  ok  |  ok  |  ok  |
[    0.000000]          soft-safe-A + irqs-on/21:  ok  |  ok  |  ok  |
[    0.000000]     hard-safe-A + unsafe-B #1/123:  ok  |  ok  |  ok  |
[    0.000000]     soft-safe-A + unsafe-B #1/123:  ok  |  ok  |  ok  |

With probes:

[    0.000000]      hard-irqs-on + irq-safe-A/21:  ok  |  ok  |  ok  |
[    0.000000]      soft-irqs-on + irq-safe-A/21:  ok  |  ok  |  ok  |
[    0.000000]        sirq-safe-A => hirqs-on/12:FAILED|FAILED|  ok  |
[    0.000000]        sirq-safe-A => hirqs-on/21:FAILED|FAILED|  ok  |
[    0.000000]          hard-safe-A + irqs-on/12:FAILED|FAILED|  ok  |
[    0.000000]          soft-safe-A + irqs-on/12:FAILED|FAILED|  ok  |
[    0.000000]          hard-safe-A + irqs-on/21:FAILED|FAILED|  ok  |
[    0.000000]          soft-safe-A + irqs-on/21:FAILED|FAILED|  ok  |
[    0.000000]     hard-safe-A + unsafe-B #1/123:  ok  |  ok  |  ok  |
[    0.000000]     soft-safe-A + unsafe-B #1/123:  ok  |  ok  |  ok  |

Signed-off-by: Joel Fernandes (Google) <joel at joelfernandes.org>
---
 include/linux/ftrace.h            |  11 +-
 include/linux/irqflags.h          |  11 +-
 include/linux/lockdep.h           |   8 +-
 include/linux/preempt.h           |   2 +-
 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      | 213 ++++++++----------------------
 kernel/trace/trace_preemptirq.c   |  71 ++++++++++
 12 files changed, 189 insertions(+), 216 deletions(-)
 create mode 100644 kernel/trace/trace_preemptirq.c

diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
index 9c3c9a319e48..5191030af0c0 100644
--- a/include/linux/ftrace.h
+++ b/include/linux/ftrace.h
@@ -709,16 +709,7 @@ static inline unsigned long get_lock_parent_ip(void)
 	return CALLER_ADDR2;
 }
 
-#ifdef CONFIG_IRQSOFF_TRACER
-  extern void time_hardirqs_on(unsigned long a0, unsigned long a1);
-  extern void time_hardirqs_off(unsigned long a0, unsigned long a1);
-#else
-  static inline void time_hardirqs_on(unsigned long a0, unsigned long a1) { }
-  static inline void time_hardirqs_off(unsigned long a0, unsigned long a1) { }
-#endif
-
-#if defined(CONFIG_PREEMPT_TRACER) || \
-	(defined(CONFIG_DEBUG_PREEMPT) && defined(CONFIG_PREEMPTIRQ_EVENTS))
+#ifdef CONFIG_TRACE_PREEMPT_TOGGLE
   extern void trace_preempt_on(unsigned long a0, unsigned long a1);
   extern void trace_preempt_off(unsigned long a0, unsigned long a1);
 #else
diff --git a/include/linux/irqflags.h b/include/linux/irqflags.h
index 9700f00bbc04..50edb9cbbd26 100644
--- a/include/linux/irqflags.h
+++ b/include/linux/irqflags.h
@@ -15,9 +15,16 @@
 #include <linux/typecheck.h>
 #include <asm/irqflags.h>
 
-#ifdef CONFIG_TRACE_IRQFLAGS
+/* Currently trace_softirqs_on/off is used only by lockdep */
+#ifdef CONFIG_PROVE_LOCKING
   extern void trace_softirqs_on(unsigned long ip);
   extern void trace_softirqs_off(unsigned long ip);
+#else
+# define trace_softirqs_on(ip)	do { } while (0)
+# define trace_softirqs_off(ip)	do { } while (0)
+#endif
+
+#ifdef CONFIG_TRACE_IRQFLAGS
   extern void trace_hardirqs_on(void);
   extern void trace_hardirqs_off(void);
 # define trace_hardirq_context(p)	((p)->hardirq_context)
@@ -43,8 +50,6 @@ do {						\
 #else
 # define trace_hardirqs_on()		do { } while (0)
 # define trace_hardirqs_off()		do { } while (0)
-# define trace_softirqs_on(ip)		do { } while (0)
-# define trace_softirqs_off(ip)		do { } while (0)
 # define trace_hardirq_context(p)	0
 # define trace_softirq_context(p)	0
 # define trace_hardirqs_enabled(p)	0
diff --git a/include/linux/lockdep.h b/include/linux/lockdep.h
index 6fc77d4dbdcd..a8113357ceeb 100644
--- a/include/linux/lockdep.h
+++ b/include/linux/lockdep.h
@@ -266,7 +266,8 @@ struct held_lock {
 /*
  * Initialization, self-test and debugging-output methods:
  */
-extern void lockdep_info(void);
+extern void lockdep_init(void);
+extern void lockdep_init_early(void);
 extern void lockdep_reset(void);
 extern void lockdep_reset_lock(struct lockdep_map *lock);
 extern void lockdep_free_key_range(void *start, unsigned long size);
@@ -406,7 +407,8 @@ static inline void lockdep_on(void)
 # define lock_downgrade(l, i)			do { } while (0)
 # define lock_set_class(l, n, k, s, i)		do { } while (0)
 # define lock_set_subclass(l, s, i)		do { } while (0)
-# define lockdep_info()				do { } while (0)
+# define lockdep_init()				do { } while (0)
+# define lockdep_init_early()			do { } while (0)
 # define lockdep_init_map(lock, name, key, sub) \
 		do { (void)(name); (void)(key); } while (0)
 # define lockdep_set_class(lock, key)		do { (void)(key); } while (0)
@@ -532,7 +534,7 @@ do {								\
 
 #endif /* CONFIG_LOCKDEP */
 
-#ifdef CONFIG_TRACE_IRQFLAGS
+#ifdef CONFIG_PROVE_LOCKING
 extern void print_irqtrace_events(struct task_struct *curr);
 #else
 static inline void print_irqtrace_events(struct task_struct *curr)
diff --git a/include/linux/preempt.h b/include/linux/preempt.h
index 5bd3f151da78..c01813c3fbe9 100644
--- a/include/linux/preempt.h
+++ b/include/linux/preempt.h
@@ -150,7 +150,7 @@
  */
 #define in_atomic_preempt_off() (preempt_count() != PREEMPT_DISABLE_OFFSET)
 
-#if defined(CONFIG_DEBUG_PREEMPT) || defined(CONFIG_PREEMPT_TRACER)
+#if defined(CONFIG_DEBUG_PREEMPT) || defined(CONFIG_TRACE_PREEMPT_TOGGLE)
 extern void preempt_count_add(int val);
 extern void preempt_count_sub(int val);
 #define preempt_count_dec_and_test() \
diff --git a/include/trace/events/preemptirq.h b/include/trace/events/preemptirq.h
index 9c4eb33c5a1d..9a0d4ceeb166 100644
--- a/include/trace/events/preemptirq.h
+++ b/include/trace/events/preemptirq.h
@@ -1,4 +1,4 @@
-#ifdef CONFIG_PREEMPTIRQ_EVENTS
+#ifdef CONFIG_PREEMPTIRQ_TRACEPOINTS
 
 #undef TRACE_SYSTEM
 #define TRACE_SYSTEM preemptirq
@@ -32,7 +32,7 @@ DECLARE_EVENT_CLASS(preemptirq_template,
 		  (void *)((unsigned long)(_stext) + __entry->parent_offs))
 );
 
-#ifndef CONFIG_PROVE_LOCKING
+#ifdef CONFIG_TRACE_IRQFLAGS
 DEFINE_EVENT(preemptirq_template, irq_disable,
 	     TP_PROTO(unsigned long ip, unsigned long parent_ip),
 	     TP_ARGS(ip, parent_ip));
@@ -40,9 +40,14 @@ DEFINE_EVENT(preemptirq_template, irq_disable,
 DEFINE_EVENT(preemptirq_template, irq_enable,
 	     TP_PROTO(unsigned long ip, unsigned long parent_ip),
 	     TP_ARGS(ip, parent_ip));
+#else
+#define trace_irq_enable(...)
+#define trace_irq_disable(...)
+#define trace_irq_enable_rcuidle(...)
+#define trace_irq_disable_rcuidle(...)
 #endif
 
-#ifdef CONFIG_DEBUG_PREEMPT
+#ifdef CONFIG_TRACE_PREEMPT_TOGGLE
 DEFINE_EVENT(preemptirq_template, preempt_disable,
 	     TP_PROTO(unsigned long ip, unsigned long parent_ip),
 	     TP_ARGS(ip, parent_ip));
@@ -50,22 +55,22 @@ DEFINE_EVENT(preemptirq_template, preempt_disable,
 DEFINE_EVENT(preemptirq_template, preempt_enable,
 	     TP_PROTO(unsigned long ip, unsigned long parent_ip),
 	     TP_ARGS(ip, parent_ip));
+#else
+#define trace_preempt_enable(...)
+#define trace_preempt_disable(...)
+#define trace_preempt_enable_rcuidle(...)
+#define trace_preempt_disable_rcuidle(...)
 #endif
 
 #endif /* _TRACE_PREEMPTIRQ_H */
 
 #include <trace/define_trace.h>
 
-#endif /* !CONFIG_PREEMPTIRQ_EVENTS */
-
-#if !defined(CONFIG_PREEMPTIRQ_EVENTS) || defined(CONFIG_PROVE_LOCKING)
+#else /* !CONFIG_PREEMPTIRQ_TRACEPOINTS */
 #define trace_irq_enable(...)
 #define trace_irq_disable(...)
 #define trace_irq_enable_rcuidle(...)
 #define trace_irq_disable_rcuidle(...)
-#endif
-
-#if !defined(CONFIG_PREEMPTIRQ_EVENTS) || !defined(CONFIG_DEBUG_PREEMPT)
 #define trace_preempt_enable(...)
 #define trace_preempt_disable(...)
 #define trace_preempt_enable_rcuidle(...)
diff --git a/init/main.c b/init/main.c
index fd37315835b4..5181c5bc2f0c 100644
--- a/init/main.c
+++ b/init/main.c
@@ -647,6 +647,9 @@ asmlinkage __visible void __init start_kernel(void)
 	profile_init();
 	call_function_init();
 	WARN(!irqs_disabled(), "Interrupts were enabled early\n");
+
+	lockdep_init_early();
+
 	early_boot_irqs_disabled = false;
 	local_irq_enable();
 
@@ -662,7 +665,7 @@ asmlinkage __visible void __init start_kernel(void)
 		panic("Too many boot %s vars at `%s'", panic_later,
 		      panic_param);
 
-	lockdep_info();
+	lockdep_init();
 
 	/*
 	 * Need to run this when irqs are enabled, because it wants
diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index 023386338269..871a42232858 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -55,6 +55,7 @@
 
 #include "lockdep_internals.h"
 
+#include <trace/events/preemptirq.h>
 #define CREATE_TRACE_POINTS
 #include <trace/events/lock.h>
 
@@ -2841,10 +2842,9 @@ static void __trace_hardirqs_on_caller(unsigned long ip)
 	debug_atomic_inc(hardirqs_on_events);
 }
 
-__visible void trace_hardirqs_on_caller(unsigned long ip)
+static void lockdep_hardirqs_on(void *none, unsigned long ignore,
+				unsigned long ip)
 {
-	time_hardirqs_on(CALLER_ADDR0, ip);
-
 	if (unlikely(!debug_locks || current->lockdep_recursion))
 		return;
 
@@ -2883,23 +2883,15 @@ __visible void trace_hardirqs_on_caller(unsigned long ip)
 	__trace_hardirqs_on_caller(ip);
 	current->lockdep_recursion = 0;
 }
-EXPORT_SYMBOL(trace_hardirqs_on_caller);
-
-void trace_hardirqs_on(void)
-{
-	trace_hardirqs_on_caller(CALLER_ADDR0);
-}
-EXPORT_SYMBOL(trace_hardirqs_on);
 
 /*
  * Hardirqs were disabled:
  */
-__visible void trace_hardirqs_off_caller(unsigned long ip)
+static void lockdep_hardirqs_off(void *none, unsigned long ignore,
+				 unsigned long ip)
 {
 	struct task_struct *curr = current;
 
-	time_hardirqs_off(CALLER_ADDR0, ip);
-
 	if (unlikely(!debug_locks || current->lockdep_recursion))
 		return;
 
@@ -2921,13 +2913,6 @@ __visible void trace_hardirqs_off_caller(unsigned long ip)
 	} else
 		debug_atomic_inc(redundant_hardirqs_off);
 }
-EXPORT_SYMBOL(trace_hardirqs_off_caller);
-
-void trace_hardirqs_off(void)
-{
-	trace_hardirqs_off_caller(CALLER_ADDR0);
-}
-EXPORT_SYMBOL(trace_hardirqs_off);
 
 /*
  * Softirqs will be enabled:
@@ -4334,7 +4319,15 @@ void lockdep_reset_lock(struct lockdep_map *lock)
 	raw_local_irq_restore(flags);
 }
 
-void __init lockdep_info(void)
+void __init lockdep_init_early(void)
+{
+#ifdef CONFIG_PROVE_LOCKING
+	register_trace_prio_irq_disable(lockdep_hardirqs_off, NULL, INT_MAX);
+	register_trace_prio_irq_enable(lockdep_hardirqs_on, NULL, INT_MIN);
+#endif
+}
+
+void __init lockdep_init(void)
 {
 	printk("Lock dependency validator: Copyright (c) 2006 Red Hat, Inc., Ingo Molnar\n");
 
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 092f7c4de903..4e9c2d254fba 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -3189,7 +3189,7 @@ static inline void sched_tick_stop(int cpu) { }
 #endif
 
 #if defined(CONFIG_PREEMPT) && (defined(CONFIG_DEBUG_PREEMPT) || \
-				defined(CONFIG_PREEMPT_TRACER))
+				defined(CONFIG_TRACE_PREEMPT_TOGGLE))
 /*
  * If the value passed in is equal to the current preempt count
  * then we just disabled preemption. Start timing the latency.
diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig
index c4f0f2e4126e..0bcba2a76ad9 100644
--- a/kernel/trace/Kconfig
+++ b/kernel/trace/Kconfig
@@ -82,6 +82,15 @@ config RING_BUFFER_ALLOW_SWAP
 	 Allow the use of ring_buffer_swap_cpu.
 	 Adds a very slight overhead to tracing when enabled.
 
+config PREEMPTIRQ_TRACEPOINTS
+	bool
+	depends on TRACE_PREEMPT_TOGGLE || TRACE_IRQFLAGS
+	select TRACING
+	default y
+	help
+	  Create preempt/irq toggle tracepoints if needed, so that other parts
+	  of the kernel can use them to generate or add hooks to them.
+
 # All tracer options should select GENERIC_TRACER. For those options that are
 # enabled by all tracers (context switch and event tracer) they select TRACING.
 # This allows those options to appear when no other tracer is selected. But the
@@ -159,18 +168,20 @@ config FUNCTION_GRAPH_TRACER
 	  the return value. This is done by setting the current return
 	  address on the current task structure into a stack of calls.
 
+config TRACE_PREEMPT_TOGGLE
+	bool
+	help
+	  Enables hooks which will be called when preemption is first disabled,
+	  and last enabled.
 
 config PREEMPTIRQ_EVENTS
 	bool "Enable trace events for preempt and irq disable/enable"
 	select TRACE_IRQFLAGS
-	depends on DEBUG_PREEMPT || !PROVE_LOCKING
-	depends on TRACING
+	select TRACE_PREEMPT_TOGGLE if PREEMPT
+	select GENERIC_TRACER
 	default n
 	help
 	  Enable tracing of disable and enable events for preemption and irqs.
-	  For tracing preempt disable/enable events, DEBUG_PREEMPT must be
-	  enabled. For tracing irq disable/enable events, PROVE_LOCKING must
-	  be disabled.
 
 config IRQSOFF_TRACER
 	bool "Interrupts-off Latency Tracer"
@@ -207,6 +218,7 @@ config PREEMPT_TRACER
 	select RING_BUFFER_ALLOW_SWAP
 	select TRACER_SNAPSHOT
 	select TRACER_SNAPSHOT_PER_CPU_SWAP
+	select TRACE_PREEMPT_TOGGLE
 	help
 	  This option measures the time spent in preemption-off critical
 	  sections, with microsecond accuracy.
diff --git a/kernel/trace/Makefile b/kernel/trace/Makefile
index e2538c7638d4..84a0cb222f20 100644
--- a/kernel/trace/Makefile
+++ b/kernel/trace/Makefile
@@ -35,7 +35,7 @@ obj-$(CONFIG_TRACING) += trace_printk.o
 obj-$(CONFIG_TRACING_MAP) += tracing_map.o
 obj-$(CONFIG_CONTEXT_SWITCH_TRACER) += trace_sched_switch.o
 obj-$(CONFIG_FUNCTION_TRACER) += trace_functions.o
-obj-$(CONFIG_PREEMPTIRQ_EVENTS) += trace_irqsoff.o
+obj-$(CONFIG_PREEMPTIRQ_TRACEPOINTS) += trace_preemptirq.o
 obj-$(CONFIG_IRQSOFF_TRACER) += trace_irqsoff.o
 obj-$(CONFIG_PREEMPT_TRACER) += trace_irqsoff.o
 obj-$(CONFIG_SCHED_TRACER) += trace_sched_wakeup.o
diff --git a/kernel/trace/trace_irqsoff.c b/kernel/trace/trace_irqsoff.c
index f8daa754cce2..d2d8284088f0 100644
--- a/kernel/trace/trace_irqsoff.c
+++ b/kernel/trace/trace_irqsoff.c
@@ -16,7 +16,6 @@
 
 #include "trace.h"
 
-#define CREATE_TRACE_POINTS
 #include <trace/events/preemptirq.h>
 
 #if defined(CONFIG_IRQSOFF_TRACER) || defined(CONFIG_PREEMPT_TRACER)
@@ -450,66 +449,6 @@ void stop_critical_timings(void)
 }
 EXPORT_SYMBOL_GPL(stop_critical_timings);
 
-#ifdef CONFIG_IRQSOFF_TRACER
-#ifdef CONFIG_PROVE_LOCKING
-void time_hardirqs_on(unsigned long a0, unsigned long a1)
-{
-	if (!preempt_trace() && irq_trace())
-		stop_critical_timing(a0, a1);
-}
-
-void time_hardirqs_off(unsigned long a0, unsigned long a1)
-{
-	if (!preempt_trace() && irq_trace())
-		start_critical_timing(a0, a1);
-}
-
-#else /* !CONFIG_PROVE_LOCKING */
-
-/*
- * We are only interested in hardirq on/off events:
- */
-static inline void tracer_hardirqs_on(void)
-{
-	if (!preempt_trace() && irq_trace())
-		stop_critical_timing(CALLER_ADDR0, CALLER_ADDR1);
-}
-
-static inline void tracer_hardirqs_off(void)
-{
-	if (!preempt_trace() && irq_trace())
-		start_critical_timing(CALLER_ADDR0, CALLER_ADDR1);
-}
-
-static inline void tracer_hardirqs_on_caller(unsigned long caller_addr)
-{
-	if (!preempt_trace() && irq_trace())
-		stop_critical_timing(CALLER_ADDR0, caller_addr);
-}
-
-static inline void tracer_hardirqs_off_caller(unsigned long caller_addr)
-{
-	if (!preempt_trace() && irq_trace())
-		start_critical_timing(CALLER_ADDR0, caller_addr);
-}
-
-#endif /* CONFIG_PROVE_LOCKING */
-#endif /*  CONFIG_IRQSOFF_TRACER */
-
-#ifdef CONFIG_PREEMPT_TRACER
-static inline void tracer_preempt_on(unsigned long a0, unsigned long a1)
-{
-	if (preempt_trace() && !irq_trace())
-		stop_critical_timing(a0, a1);
-}
-
-static inline void tracer_preempt_off(unsigned long a0, unsigned long a1)
-{
-	if (preempt_trace() && !irq_trace())
-		start_critical_timing(a0, a1);
-}
-#endif /* CONFIG_PREEMPT_TRACER */
-
 #ifdef CONFIG_FUNCTION_TRACER
 static bool function_enabled;
 
@@ -659,15 +598,34 @@ static void irqsoff_tracer_stop(struct trace_array *tr)
 }
 
 #ifdef CONFIG_IRQSOFF_TRACER
+/*
+ * We are only interested in hardirq on/off events:
+ */
+static void tracer_hardirqs_on(void *none, unsigned long a0, unsigned long a1)
+{
+	if (!preempt_trace() && irq_trace())
+		stop_critical_timing(a0, a1);
+}
+
+static void tracer_hardirqs_off(void *none, unsigned long a0, unsigned long a1)
+{
+	if (!preempt_trace() && irq_trace())
+		start_critical_timing(a0, a1);
+}
+
 static int irqsoff_tracer_init(struct trace_array *tr)
 {
 	trace_type = TRACER_IRQS_OFF;
 
+	register_trace_irq_disable(tracer_hardirqs_off, NULL);
+	register_trace_irq_enable(tracer_hardirqs_on, NULL);
 	return __irqsoff_tracer_init(tr);
 }
 
 static void irqsoff_tracer_reset(struct trace_array *tr)
 {
+	unregister_trace_irq_disable(tracer_hardirqs_off, NULL);
+	unregister_trace_irq_enable(tracer_hardirqs_on, NULL);
 	__irqsoff_tracer_reset(tr);
 }
 
@@ -692,19 +650,37 @@ static struct tracer irqsoff_tracer __read_mostly =
 };
 # define register_irqsoff(trace) register_tracer(&trace)
 #else
+static inline void tracer_hardirqs_on(unsigned long a0, unsigned long a1) { }
+static inline void tracer_hardirqs_off(unsigned long a0, unsigned long a1) { }
 # define register_irqsoff(trace) do { } while (0)
-#endif
+#endif /*  CONFIG_IRQSOFF_TRACER */
 
 #ifdef CONFIG_PREEMPT_TRACER
+static void tracer_preempt_on(void *none, unsigned long a0, unsigned long a1)
+{
+	if (preempt_trace() && !irq_trace())
+		stop_critical_timing(a0, a1);
+}
+
+static void tracer_preempt_off(void *none, unsigned long a0, unsigned long a1)
+{
+	if (preempt_trace() && !irq_trace())
+		start_critical_timing(a0, a1);
+}
+
 static int preemptoff_tracer_init(struct trace_array *tr)
 {
 	trace_type = TRACER_PREEMPT_OFF;
 
+	register_trace_preempt_disable(tracer_preempt_off, NULL);
+	register_trace_preempt_enable(tracer_preempt_on, NULL);
 	return __irqsoff_tracer_init(tr);
 }
 
 static void preemptoff_tracer_reset(struct trace_array *tr)
 {
+	unregister_trace_preempt_disable(tracer_preempt_off, NULL);
+	unregister_trace_preempt_enable(tracer_preempt_on, NULL);
 	__irqsoff_tracer_reset(tr);
 }
 
@@ -729,21 +705,32 @@ static struct tracer preemptoff_tracer __read_mostly =
 };
 # define register_preemptoff(trace) register_tracer(&trace)
 #else
+static inline void tracer_preempt_on(unsigned long a0, unsigned long a1) { }
+static inline void tracer_preempt_off(unsigned long a0, unsigned long a1) { }
 # define register_preemptoff(trace) do { } while (0)
-#endif
+#endif /* CONFIG_PREEMPT_TRACER */
 
-#if defined(CONFIG_IRQSOFF_TRACER) && \
-	defined(CONFIG_PREEMPT_TRACER)
+#if defined(CONFIG_IRQSOFF_TRACER) && defined(CONFIG_PREEMPT_TRACER)
 
 static int preemptirqsoff_tracer_init(struct trace_array *tr)
 {
 	trace_type = TRACER_IRQS_OFF | TRACER_PREEMPT_OFF;
 
+	register_trace_irq_disable(tracer_hardirqs_off, NULL);
+	register_trace_irq_enable(tracer_hardirqs_on, NULL);
+	register_trace_preempt_disable(tracer_preempt_off, NULL);
+	register_trace_preempt_enable(tracer_preempt_on, NULL);
+
 	return __irqsoff_tracer_init(tr);
 }
 
 static void preemptirqsoff_tracer_reset(struct trace_array *tr)
 {
+	unregister_trace_irq_disable(tracer_hardirqs_off, NULL);
+	unregister_trace_irq_enable(tracer_hardirqs_on, NULL);
+	unregister_trace_preempt_disable(tracer_preempt_off, NULL);
+	unregister_trace_preempt_enable(tracer_preempt_on, NULL);
+
 	__irqsoff_tracer_reset(tr);
 }
 
@@ -782,99 +769,3 @@ __init static int init_irqsoff_tracer(void)
 }
 core_initcall(init_irqsoff_tracer);
 #endif /* IRQSOFF_TRACER || PREEMPTOFF_TRACER */
-
-#ifndef CONFIG_IRQSOFF_TRACER
-static inline void tracer_hardirqs_on(void) { }
-static inline void tracer_hardirqs_off(void) { }
-static inline void tracer_hardirqs_on_caller(unsigned long caller_addr) { }
-static inline void tracer_hardirqs_off_caller(unsigned long caller_addr) { }
-#endif
-
-#ifndef CONFIG_PREEMPT_TRACER
-static inline void tracer_preempt_on(unsigned long a0, unsigned long a1) { }
-static inline void tracer_preempt_off(unsigned long a0, unsigned long a1) { }
-#endif
-
-#if defined(CONFIG_TRACE_IRQFLAGS) && !defined(CONFIG_PROVE_LOCKING)
-/* Per-cpu variable to prevent redundant calls when IRQs already off */
-static DEFINE_PER_CPU(int, tracing_irq_cpu);
-
-void trace_hardirqs_on(void)
-{
-	if (!this_cpu_read(tracing_irq_cpu))
-		return;
-
-	trace_irq_enable_rcuidle(CALLER_ADDR0, CALLER_ADDR1);
-	tracer_hardirqs_on();
-
-	this_cpu_write(tracing_irq_cpu, 0);
-}
-EXPORT_SYMBOL(trace_hardirqs_on);
-
-void trace_hardirqs_off(void)
-{
-	if (this_cpu_read(tracing_irq_cpu))
-		return;
-
-	this_cpu_write(tracing_irq_cpu, 1);
-
-	trace_irq_disable_rcuidle(CALLER_ADDR0, CALLER_ADDR1);
-	tracer_hardirqs_off();
-}
-EXPORT_SYMBOL(trace_hardirqs_off);
-
-__visible void trace_hardirqs_on_caller(unsigned long caller_addr)
-{
-	if (!this_cpu_read(tracing_irq_cpu))
-		return;
-
-	trace_irq_enable_rcuidle(CALLER_ADDR0, caller_addr);
-	tracer_hardirqs_on_caller(caller_addr);
-
-	this_cpu_write(tracing_irq_cpu, 0);
-}
-EXPORT_SYMBOL(trace_hardirqs_on_caller);
-
-__visible void trace_hardirqs_off_caller(unsigned long caller_addr)
-{
-	if (this_cpu_read(tracing_irq_cpu))
-		return;
-
-	this_cpu_write(tracing_irq_cpu, 1);
-
-	trace_irq_disable_rcuidle(CALLER_ADDR0, caller_addr);
-	tracer_hardirqs_off_caller(caller_addr);
-}
-EXPORT_SYMBOL(trace_hardirqs_off_caller);
-
-/*
- * Stubs:
- */
-
-void trace_softirqs_on(unsigned long ip)
-{
-}
-
-void trace_softirqs_off(unsigned long ip)
-{
-}
-
-inline void print_irqtrace_events(struct task_struct *curr)
-{
-}
-#endif
-
-#if defined(CONFIG_PREEMPT_TRACER) || \
-	(defined(CONFIG_DEBUG_PREEMPT) && defined(CONFIG_PREEMPTIRQ_EVENTS))
-void trace_preempt_on(unsigned long a0, unsigned long a1)
-{
-	trace_preempt_enable_rcuidle(a0, a1);
-	tracer_preempt_on(a0, a1);
-}
-
-void trace_preempt_off(unsigned long a0, unsigned long a1)
-{
-	trace_preempt_disable_rcuidle(a0, a1);
-	tracer_preempt_off(a0, a1);
-}
-#endif
diff --git a/kernel/trace/trace_preemptirq.c b/kernel/trace/trace_preemptirq.c
new file mode 100644
index 000000000000..dc01c7f4d326
--- /dev/null
+++ b/kernel/trace/trace_preemptirq.c
@@ -0,0 +1,71 @@
+/*
+ * preemptoff and irqoff tracepoints
+ *
+ * Copyright (C) Joel Fernandes (Google) <joel at joelfernandes.org>
+ */
+
+#include <linux/kallsyms.h>
+#include <linux/uaccess.h>
+#include <linux/module.h>
+#include <linux/ftrace.h>
+
+#define CREATE_TRACE_POINTS
+#include <trace/events/preemptirq.h>
+
+#ifdef CONFIG_TRACE_IRQFLAGS
+/* Per-cpu variable to prevent redundant calls when IRQs already off */
+static DEFINE_PER_CPU(int, tracing_irq_cpu);
+
+void trace_hardirqs_on(void)
+{
+	if (lockdep_recursing(current) || !this_cpu_read(tracing_irq_cpu))
+		return;
+
+	trace_irq_enable_rcuidle(CALLER_ADDR0, CALLER_ADDR1);
+	this_cpu_write(tracing_irq_cpu, 0);
+}
+EXPORT_SYMBOL(trace_hardirqs_on);
+
+void trace_hardirqs_off(void)
+{
+	if (lockdep_recursing(current) || this_cpu_read(tracing_irq_cpu))
+		return;
+
+	this_cpu_write(tracing_irq_cpu, 1);
+	trace_irq_disable_rcuidle(CALLER_ADDR0, CALLER_ADDR1);
+}
+EXPORT_SYMBOL(trace_hardirqs_off);
+
+__visible void trace_hardirqs_on_caller(unsigned long caller_addr)
+{
+	if (lockdep_recursing(current) || !this_cpu_read(tracing_irq_cpu))
+		return;
+
+	trace_irq_enable_rcuidle(CALLER_ADDR0, caller_addr);
+	this_cpu_write(tracing_irq_cpu, 0);
+}
+EXPORT_SYMBOL(trace_hardirqs_on_caller);
+
+__visible void trace_hardirqs_off_caller(unsigned long caller_addr)
+{
+	if (lockdep_recursing(current) || this_cpu_read(tracing_irq_cpu))
+		return;
+
+	this_cpu_write(tracing_irq_cpu, 1);
+	trace_irq_disable_rcuidle(CALLER_ADDR0, caller_addr);
+}
+EXPORT_SYMBOL(trace_hardirqs_off_caller);
+#endif /* CONFIG_TRACE_IRQFLAGS */
+
+#ifdef CONFIG_TRACE_PREEMPT_TOGGLE
+
+void trace_preempt_on(unsigned long a0, unsigned long a1)
+{
+	trace_preempt_enable_rcuidle(a0, a1);
+}
+
+void trace_preempt_off(unsigned long a0, unsigned long a1)
+{
+	trace_preempt_disable_rcuidle(a0, a1);
+}
+#endif
-- 
2.17.0.441.gb46fe60e1d-goog

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^ permalink raw reply	[flat|nested] 33+ messages in thread

* [PATCH v7 7/8] lib: Add module to simulate atomic sections for testing preemptoff tracers
  2018-05-24  1:21 ` joelaf
  (?)
@ 2018-05-24  1:21   ` joelaf
  -1 siblings, 0 replies; 33+ messages in thread
From: Joel Fernandes @ 2018-05-24  1:21 UTC (permalink / raw)
  To: linux-kernel
  Cc: kernel-team, Joel Fernandes (Google),
	Boqun Feng, Byungchul Park, Erick Reyes, Ingo Molnar,
	Julia Cartwright, linux-kselftest, Masami Hiramatsu,
	Mathieu Desnoyers, Namhyung Kim, Paul McKenney, Peter Zijlstra,
	Shuah Khan, Steven Rostedt, Thomas Glexiner, Todd Kjos,
	Tom Zanussi

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

In this patch we introduce a test module for simulating a long atomic
section in the kernel which the preemptoff or irqsoff tracers can
detect. This module is to be used only for test purposes and is default
disabled.

Following is the expected output (only briefly shown) that can be parsed
to verify that the tracers are working correctly. We will use this from
the kselftests in future patches.

For the preemptoff tracer:

echo preemptoff > /d/tracing/current_tracer
sleep 1
insmod ./test_atomic_sections.ko atomic_mode=preempt atomic_time=500000
sleep 1
bash-4.3# cat /d/tracing/trace
preempt -1066    2...2    0us@: atomic_sect_run <-atomic_sect_run
preempt -1066    2...2 500002us : atomic_sect_run <-atomic_sect_run
preempt -1066    2...2 500004us : tracer_preempt_on <-atomic_sect_run
preempt -1066    2...2 500012us : <stack trace>
 => kthread
 => ret_from_fork

For the irqsoff tracer:

echo irqsoff > /d/tracing/current_tracer
sleep 1
insmod ./test_atomic_sections.ko atomic_mode=irq atomic_time=500000
sleep 1
bash-4.3# cat /d/tracing/trace
irq dis -1069    1d..1    0us@: atomic_sect_run
irq dis -1069    1d..1 500001us : atomic_sect_run
irq dis -1069    1d..1 500002us : tracer_hardirqs_on <-atomic_sect_run
irq dis -1069    1d..1 500005us : <stack trace>
 => ret_from_fork

Co-authored-by: Erick Reyes <erickreyes@google.com>
Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
---
 lib/Kconfig.debug          |  8 ++++
 lib/Makefile               |  1 +
 lib/test_atomic_sections.c | 79 ++++++++++++++++++++++++++++++++++++++
 3 files changed, 88 insertions(+)
 create mode 100644 lib/test_atomic_sections.c

diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index c40c7b734cd1..faebf0fe3bcf 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -1933,6 +1933,14 @@ config TEST_KMOD
 
 	  If unsure, say N.
 
+config TEST_ATOMIC_SECTIONS
+	tristate "Simulate atomic sections for tracers to detect"
+	depends on m
+	help
+	  Select this option to build a test module that can help test atomic
+	  sections by simulating them with a duration supplied as a module
+	  parameter. Preempt disable and irq disable modes can be requested.
+
 config TEST_DEBUG_VIRTUAL
 	tristate "Test CONFIG_DEBUG_VIRTUAL feature"
 	depends on DEBUG_VIRTUAL
diff --git a/lib/Makefile b/lib/Makefile
index ce20696d5a92..e82cf5445b7b 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -46,6 +46,7 @@ obj-y += string_helpers.o
 obj-$(CONFIG_TEST_STRING_HELPERS) += test-string_helpers.o
 obj-y += hexdump.o
 obj-$(CONFIG_TEST_HEXDUMP) += test_hexdump.o
+obj-$(CONFIG_TEST_ATOMIC_SECTIONS) += test_atomic_sections.o
 obj-y += kstrtox.o
 obj-$(CONFIG_FIND_BIT_BENCHMARK) += find_bit_benchmark.o
 obj-$(CONFIG_TEST_BPF) += test_bpf.o
diff --git a/lib/test_atomic_sections.c b/lib/test_atomic_sections.c
new file mode 100644
index 000000000000..2c8c6419d183
--- /dev/null
+++ b/lib/test_atomic_sections.c
@@ -0,0 +1,79 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Atomic section emulation test module
+ *
+ * Emulates atomic sections by disabling IRQs or preemption
+ * and doing a busy wait for a specified amount of time.
+ * This can be used for testing of different atomic section
+ * tracers such as irqsoff tracers.
+ *
+ * (c) 2018. Google LLC
+ */
+
+#include <linux/delay.h>
+#include <linux/interrupt.h>
+#include <linux/irq.h>
+#include <linux/kernel.h>
+#include <linux/kthread.h>
+#include <linux/ktime.h>
+#include <linux/module.h>
+#include <linux/printk.h>
+#include <linux/string.h>
+
+static int atomic_time = 100;
+static char atomic_mode[10] = "irq";
+
+module_param_named(atomic_time, atomic_time, int, S_IRUGO);
+module_param_string(atomic_mode, atomic_mode, 10, S_IRUGO);
+MODULE_PARM_DESC(atomic_time, "Period in microseconds (100 uS default)");
+MODULE_PARM_DESC(atomic_mode, "Mode of the test such as preempt or irq (default irq)");
+
+static void busy_wait(int time)
+{
+	ktime_t start, end;
+	start = ktime_get();
+	do {
+		end = ktime_get();
+		if (kthread_should_stop())
+			break;
+	} while (ktime_to_ns(ktime_sub(end, start)) < (time * 1000));
+}
+
+void atomic_sect_run(void *data)
+{
+	unsigned long flags;
+
+	if (!strcmp(atomic_mode, "irq")) {
+		local_irq_save(flags);
+		busy_wait(atomic_time);
+		local_irq_restore(flags);
+	} else if (!strcmp(atomic_mode, "preempt")) {
+		preempt_disable();
+		busy_wait(atomic_time);
+		preempt_enable();
+	}
+	do_exit(0);
+}
+
+static int __init atomic_sect_init(void)
+{
+	char task_name[50];
+	struct task_struct *test_task;
+
+	snprintf(task_name, 50, "%s dis test", atomic_mode);
+
+	test_task = kthread_run((void*)atomic_sect_run, NULL, task_name);
+	if (IS_ERR(test_task))
+		return PTR_ERR(test_task);
+
+	return 0;
+}
+
+static void __exit atomic_sect_exit(void)
+{
+	return;
+}
+
+module_init(atomic_sect_init)
+module_exit(atomic_sect_exit)
+MODULE_LICENSE("GPL");
-- 
2.17.0.441.gb46fe60e1d-goog

^ permalink raw reply	[flat|nested] 33+ messages in thread

* [PATCH v7 7/8] lib: Add module to simulate atomic sections for testing preemptoff tracers
@ 2018-05-24  1:21   ` joelaf
  0 siblings, 0 replies; 33+ messages in thread
From: joelaf @ 2018-05-24  1:21 UTC (permalink / raw)


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

In this patch we introduce a test module for simulating a long atomic
section in the kernel which the preemptoff or irqsoff tracers can
detect. This module is to be used only for test purposes and is default
disabled.

Following is the expected output (only briefly shown) that can be parsed
to verify that the tracers are working correctly. We will use this from
the kselftests in future patches.

For the preemptoff tracer:

echo preemptoff > /d/tracing/current_tracer
sleep 1
insmod ./test_atomic_sections.ko atomic_mode=preempt atomic_time=500000
sleep 1
bash-4.3# cat /d/tracing/trace
preempt -1066    2...2    0us@: atomic_sect_run <-atomic_sect_run
preempt -1066    2...2 500002us : atomic_sect_run <-atomic_sect_run
preempt -1066    2...2 500004us : tracer_preempt_on <-atomic_sect_run
preempt -1066    2...2 500012us : <stack trace>
 => kthread
 => ret_from_fork

For the irqsoff tracer:

echo irqsoff > /d/tracing/current_tracer
sleep 1
insmod ./test_atomic_sections.ko atomic_mode=irq atomic_time=500000
sleep 1
bash-4.3# cat /d/tracing/trace
irq dis -1069    1d..1    0us@: atomic_sect_run
irq dis -1069    1d..1 500001us : atomic_sect_run
irq dis -1069    1d..1 500002us : tracer_hardirqs_on <-atomic_sect_run
irq dis -1069    1d..1 500005us : <stack trace>
 => ret_from_fork

Co-authored-by: Erick Reyes <erickreyes at google.com>
Signed-off-by: Joel Fernandes (Google) <joel at joelfernandes.org>
---
 lib/Kconfig.debug          |  8 ++++
 lib/Makefile               |  1 +
 lib/test_atomic_sections.c | 79 ++++++++++++++++++++++++++++++++++++++
 3 files changed, 88 insertions(+)
 create mode 100644 lib/test_atomic_sections.c

diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index c40c7b734cd1..faebf0fe3bcf 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -1933,6 +1933,14 @@ config TEST_KMOD
 
 	  If unsure, say N.
 
+config TEST_ATOMIC_SECTIONS
+	tristate "Simulate atomic sections for tracers to detect"
+	depends on m
+	help
+	  Select this option to build a test module that can help test atomic
+	  sections by simulating them with a duration supplied as a module
+	  parameter. Preempt disable and irq disable modes can be requested.
+
 config TEST_DEBUG_VIRTUAL
 	tristate "Test CONFIG_DEBUG_VIRTUAL feature"
 	depends on DEBUG_VIRTUAL
diff --git a/lib/Makefile b/lib/Makefile
index ce20696d5a92..e82cf5445b7b 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -46,6 +46,7 @@ obj-y += string_helpers.o
 obj-$(CONFIG_TEST_STRING_HELPERS) += test-string_helpers.o
 obj-y += hexdump.o
 obj-$(CONFIG_TEST_HEXDUMP) += test_hexdump.o
+obj-$(CONFIG_TEST_ATOMIC_SECTIONS) += test_atomic_sections.o
 obj-y += kstrtox.o
 obj-$(CONFIG_FIND_BIT_BENCHMARK) += find_bit_benchmark.o
 obj-$(CONFIG_TEST_BPF) += test_bpf.o
diff --git a/lib/test_atomic_sections.c b/lib/test_atomic_sections.c
new file mode 100644
index 000000000000..2c8c6419d183
--- /dev/null
+++ b/lib/test_atomic_sections.c
@@ -0,0 +1,79 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Atomic section emulation test module
+ *
+ * Emulates atomic sections by disabling IRQs or preemption
+ * and doing a busy wait for a specified amount of time.
+ * This can be used for testing of different atomic section
+ * tracers such as irqsoff tracers.
+ *
+ * (c) 2018. Google LLC
+ */
+
+#include <linux/delay.h>
+#include <linux/interrupt.h>
+#include <linux/irq.h>
+#include <linux/kernel.h>
+#include <linux/kthread.h>
+#include <linux/ktime.h>
+#include <linux/module.h>
+#include <linux/printk.h>
+#include <linux/string.h>
+
+static int atomic_time = 100;
+static char atomic_mode[10] = "irq";
+
+module_param_named(atomic_time, atomic_time, int, S_IRUGO);
+module_param_string(atomic_mode, atomic_mode, 10, S_IRUGO);
+MODULE_PARM_DESC(atomic_time, "Period in microseconds (100 uS default)");
+MODULE_PARM_DESC(atomic_mode, "Mode of the test such as preempt or irq (default irq)");
+
+static void busy_wait(int time)
+{
+	ktime_t start, end;
+	start = ktime_get();
+	do {
+		end = ktime_get();
+		if (kthread_should_stop())
+			break;
+	} while (ktime_to_ns(ktime_sub(end, start)) < (time * 1000));
+}
+
+void atomic_sect_run(void *data)
+{
+	unsigned long flags;
+
+	if (!strcmp(atomic_mode, "irq")) {
+		local_irq_save(flags);
+		busy_wait(atomic_time);
+		local_irq_restore(flags);
+	} else if (!strcmp(atomic_mode, "preempt")) {
+		preempt_disable();
+		busy_wait(atomic_time);
+		preempt_enable();
+	}
+	do_exit(0);
+}
+
+static int __init atomic_sect_init(void)
+{
+	char task_name[50];
+	struct task_struct *test_task;
+
+	snprintf(task_name, 50, "%s dis test", atomic_mode);
+
+	test_task = kthread_run((void*)atomic_sect_run, NULL, task_name);
+	if (IS_ERR(test_task))
+		return PTR_ERR(test_task);
+
+	return 0;
+}
+
+static void __exit atomic_sect_exit(void)
+{
+	return;
+}
+
+module_init(atomic_sect_init)
+module_exit(atomic_sect_exit)
+MODULE_LICENSE("GPL");
-- 
2.17.0.441.gb46fe60e1d-goog

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^ permalink raw reply	[flat|nested] 33+ messages in thread

* [PATCH v7 7/8] lib: Add module to simulate atomic sections for testing preemptoff tracers
@ 2018-05-24  1:21   ` joelaf
  0 siblings, 0 replies; 33+ messages in thread
From: Joel Fernandes @ 2018-05-24  1:21 UTC (permalink / raw)


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

In this patch we introduce a test module for simulating a long atomic
section in the kernel which the preemptoff or irqsoff tracers can
detect. This module is to be used only for test purposes and is default
disabled.

Following is the expected output (only briefly shown) that can be parsed
to verify that the tracers are working correctly. We will use this from
the kselftests in future patches.

For the preemptoff tracer:

echo preemptoff > /d/tracing/current_tracer
sleep 1
insmod ./test_atomic_sections.ko atomic_mode=preempt atomic_time=500000
sleep 1
bash-4.3# cat /d/tracing/trace
preempt -1066    2...2    0us@: atomic_sect_run <-atomic_sect_run
preempt -1066    2...2 500002us : atomic_sect_run <-atomic_sect_run
preempt -1066    2...2 500004us : tracer_preempt_on <-atomic_sect_run
preempt -1066    2...2 500012us : <stack trace>
 => kthread
 => ret_from_fork

For the irqsoff tracer:

echo irqsoff > /d/tracing/current_tracer
sleep 1
insmod ./test_atomic_sections.ko atomic_mode=irq atomic_time=500000
sleep 1
bash-4.3# cat /d/tracing/trace
irq dis -1069    1d..1    0us@: atomic_sect_run
irq dis -1069    1d..1 500001us : atomic_sect_run
irq dis -1069    1d..1 500002us : tracer_hardirqs_on <-atomic_sect_run
irq dis -1069    1d..1 500005us : <stack trace>
 => ret_from_fork

Co-authored-by: Erick Reyes <erickreyes at google.com>
Signed-off-by: Joel Fernandes (Google) <joel at joelfernandes.org>
---
 lib/Kconfig.debug          |  8 ++++
 lib/Makefile               |  1 +
 lib/test_atomic_sections.c | 79 ++++++++++++++++++++++++++++++++++++++
 3 files changed, 88 insertions(+)
 create mode 100644 lib/test_atomic_sections.c

diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index c40c7b734cd1..faebf0fe3bcf 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -1933,6 +1933,14 @@ config TEST_KMOD
 
 	  If unsure, say N.
 
+config TEST_ATOMIC_SECTIONS
+	tristate "Simulate atomic sections for tracers to detect"
+	depends on m
+	help
+	  Select this option to build a test module that can help test atomic
+	  sections by simulating them with a duration supplied as a module
+	  parameter. Preempt disable and irq disable modes can be requested.
+
 config TEST_DEBUG_VIRTUAL
 	tristate "Test CONFIG_DEBUG_VIRTUAL feature"
 	depends on DEBUG_VIRTUAL
diff --git a/lib/Makefile b/lib/Makefile
index ce20696d5a92..e82cf5445b7b 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -46,6 +46,7 @@ obj-y += string_helpers.o
 obj-$(CONFIG_TEST_STRING_HELPERS) += test-string_helpers.o
 obj-y += hexdump.o
 obj-$(CONFIG_TEST_HEXDUMP) += test_hexdump.o
+obj-$(CONFIG_TEST_ATOMIC_SECTIONS) += test_atomic_sections.o
 obj-y += kstrtox.o
 obj-$(CONFIG_FIND_BIT_BENCHMARK) += find_bit_benchmark.o
 obj-$(CONFIG_TEST_BPF) += test_bpf.o
diff --git a/lib/test_atomic_sections.c b/lib/test_atomic_sections.c
new file mode 100644
index 000000000000..2c8c6419d183
--- /dev/null
+++ b/lib/test_atomic_sections.c
@@ -0,0 +1,79 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Atomic section emulation test module
+ *
+ * Emulates atomic sections by disabling IRQs or preemption
+ * and doing a busy wait for a specified amount of time.
+ * This can be used for testing of different atomic section
+ * tracers such as irqsoff tracers.
+ *
+ * (c) 2018. Google LLC
+ */
+
+#include <linux/delay.h>
+#include <linux/interrupt.h>
+#include <linux/irq.h>
+#include <linux/kernel.h>
+#include <linux/kthread.h>
+#include <linux/ktime.h>
+#include <linux/module.h>
+#include <linux/printk.h>
+#include <linux/string.h>
+
+static int atomic_time = 100;
+static char atomic_mode[10] = "irq";
+
+module_param_named(atomic_time, atomic_time, int, S_IRUGO);
+module_param_string(atomic_mode, atomic_mode, 10, S_IRUGO);
+MODULE_PARM_DESC(atomic_time, "Period in microseconds (100 uS default)");
+MODULE_PARM_DESC(atomic_mode, "Mode of the test such as preempt or irq (default irq)");
+
+static void busy_wait(int time)
+{
+	ktime_t start, end;
+	start = ktime_get();
+	do {
+		end = ktime_get();
+		if (kthread_should_stop())
+			break;
+	} while (ktime_to_ns(ktime_sub(end, start)) < (time * 1000));
+}
+
+void atomic_sect_run(void *data)
+{
+	unsigned long flags;
+
+	if (!strcmp(atomic_mode, "irq")) {
+		local_irq_save(flags);
+		busy_wait(atomic_time);
+		local_irq_restore(flags);
+	} else if (!strcmp(atomic_mode, "preempt")) {
+		preempt_disable();
+		busy_wait(atomic_time);
+		preempt_enable();
+	}
+	do_exit(0);
+}
+
+static int __init atomic_sect_init(void)
+{
+	char task_name[50];
+	struct task_struct *test_task;
+
+	snprintf(task_name, 50, "%s dis test", atomic_mode);
+
+	test_task = kthread_run((void*)atomic_sect_run, NULL, task_name);
+	if (IS_ERR(test_task))
+		return PTR_ERR(test_task);
+
+	return 0;
+}
+
+static void __exit atomic_sect_exit(void)
+{
+	return;
+}
+
+module_init(atomic_sect_init)
+module_exit(atomic_sect_exit)
+MODULE_LICENSE("GPL");
-- 
2.17.0.441.gb46fe60e1d-goog

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^ permalink raw reply	[flat|nested] 33+ messages in thread

* [PATCH v7 8/8] kselftests: Add tests for the preemptoff and irqsoff tracers
  2018-05-24  1:21 ` joelaf
  (?)
@ 2018-05-24  1:21   ` joelaf
  -1 siblings, 0 replies; 33+ messages in thread
From: Joel Fernandes @ 2018-05-24  1:21 UTC (permalink / raw)
  To: linux-kernel
  Cc: kernel-team, Joel Fernandes (Google),
	Boqun Feng, Byungchul Park, Erick Reyes, Ingo Molnar,
	Julia Cartwright, linux-kselftest, Masami Hiramatsu,
	Mathieu Desnoyers, Namhyung Kim, Paul McKenney, Peter Zijlstra,
	Shuah Khan, Steven Rostedt, Thomas Glexiner, Todd Kjos,
	Tom Zanussi

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

Here we add unit tests for the preemptoff and irqsoff tracer by using a
kernel module introduced previously to trigger atomic sections in the
kernel.

Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
---
 tools/testing/selftests/ftrace/config         |  3 +
 .../test.d/preemptirq/irqsoff_tracer.tc       | 74 +++++++++++++++++++
 2 files changed, 77 insertions(+)
 create mode 100644 tools/testing/selftests/ftrace/test.d/preemptirq/irqsoff_tracer.tc

diff --git a/tools/testing/selftests/ftrace/config b/tools/testing/selftests/ftrace/config
index b01924c71c09..29588b328345 100644
--- a/tools/testing/selftests/ftrace/config
+++ b/tools/testing/selftests/ftrace/config
@@ -4,3 +4,6 @@ CONFIG_FUNCTION_PROFILER=y
 CONFIG_TRACER_SNAPSHOT=y
 CONFIG_STACK_TRACER=y
 CONFIG_HIST_TRIGGERS=y
+CONFIG_PREEMPT_TRACER=y
+CONFIG_IRQSOFF_TRACER=y
+CONFIG_TEST_ATOMIC_SECTIONS=m
diff --git a/tools/testing/selftests/ftrace/test.d/preemptirq/irqsoff_tracer.tc b/tools/testing/selftests/ftrace/test.d/preemptirq/irqsoff_tracer.tc
new file mode 100644
index 000000000000..1764ff22c02b
--- /dev/null
+++ b/tools/testing/selftests/ftrace/test.d/preemptirq/irqsoff_tracer.tc
@@ -0,0 +1,74 @@
+#!/bin/sh
+# SPDX-License-Identifier: GPL-2.0
+# description: test for the preemptirqsoff tracer
+
+MOD=test_atomic_sections
+
+fail() {
+    reset_tracer
+    rmmod $MOD || true
+    exit_fail
+}
+
+unsup() { #msg
+    reset_tracer
+    rmmod $MOD || true
+    echo $1
+    exit_unsupported
+}
+
+modprobe $MOD || unsup "$MOD module not available"
+rmmod $MOD
+
+grep -q "preemptoff" available_tracers || unsup "preemptoff tracer not enabled"
+grep -q "irqsoff" available_tracers || unsup "irqsoff tracer not enabled"
+
+reset_tracer
+
+# Simulate preemptoff section for half a second couple of times
+echo preemptoff > current_tracer
+sleep 1
+modprobe test_atomic_sections atomic_mode=preempt atomic_time=500000 || fail
+rmmod test_atomic_sections || fail
+modprobe test_atomic_sections atomic_mode=preempt atomic_time=500000 || fail
+rmmod test_atomic_sections || fail
+modprobe test_atomic_sections atomic_mode=preempt atomic_time=500000 || fail
+rmmod test_atomic_sections || fail
+
+cat trace
+
+# Confirm which tracer
+grep -q "tracer: preemptoff" trace || fail
+
+# Check the end of the section
+egrep -q "5.....us : <stack trace>" trace || fail
+
+# Check for 500ms of latency
+egrep -q "latency: 5..... us" trace || fail
+
+reset_tracer
+
+# Simulate irqsoff section for half a second couple of times
+echo irqsoff > current_tracer
+sleep 1
+modprobe test_atomic_sections atomic_mode=irq atomic_time=500000 || fail
+rmmod test_atomic_sections || fail
+modprobe test_atomic_sections atomic_mode=irq atomic_time=500000 || fail
+rmmod test_atomic_sections || fail
+modprobe test_atomic_sections atomic_mode=irq atomic_time=500000 || fail
+rmmod test_atomic_sections || fail
+
+cat trace
+
+# Confirm which tracer
+grep -q "tracer: irqsoff" trace || fail
+
+# Check the end of the section
+egrep -q "5.....us : <stack trace>" trace || fail
+
+# Check for 500ms of latency
+egrep -q "latency: 5..... us" trace || fail
+
+reset_tracer
+exit 0
+
-- 
2.17.0.441.gb46fe60e1d-goog

^ permalink raw reply	[flat|nested] 33+ messages in thread

* [PATCH v7 8/8] kselftests: Add tests for the preemptoff and irqsoff tracers
@ 2018-05-24  1:21   ` joelaf
  0 siblings, 0 replies; 33+ messages in thread
From: joelaf @ 2018-05-24  1:21 UTC (permalink / raw)


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

Here we add unit tests for the preemptoff and irqsoff tracer by using a
kernel module introduced previously to trigger atomic sections in the
kernel.

Signed-off-by: Joel Fernandes (Google) <joel at joelfernandes.org>
---
 tools/testing/selftests/ftrace/config         |  3 +
 .../test.d/preemptirq/irqsoff_tracer.tc       | 74 +++++++++++++++++++
 2 files changed, 77 insertions(+)
 create mode 100644 tools/testing/selftests/ftrace/test.d/preemptirq/irqsoff_tracer.tc

diff --git a/tools/testing/selftests/ftrace/config b/tools/testing/selftests/ftrace/config
index b01924c71c09..29588b328345 100644
--- a/tools/testing/selftests/ftrace/config
+++ b/tools/testing/selftests/ftrace/config
@@ -4,3 +4,6 @@ CONFIG_FUNCTION_PROFILER=y
 CONFIG_TRACER_SNAPSHOT=y
 CONFIG_STACK_TRACER=y
 CONFIG_HIST_TRIGGERS=y
+CONFIG_PREEMPT_TRACER=y
+CONFIG_IRQSOFF_TRACER=y
+CONFIG_TEST_ATOMIC_SECTIONS=m
diff --git a/tools/testing/selftests/ftrace/test.d/preemptirq/irqsoff_tracer.tc b/tools/testing/selftests/ftrace/test.d/preemptirq/irqsoff_tracer.tc
new file mode 100644
index 000000000000..1764ff22c02b
--- /dev/null
+++ b/tools/testing/selftests/ftrace/test.d/preemptirq/irqsoff_tracer.tc
@@ -0,0 +1,74 @@
+#!/bin/sh
+# SPDX-License-Identifier: GPL-2.0
+# description: test for the preemptirqsoff tracer
+
+MOD=test_atomic_sections
+
+fail() {
+    reset_tracer
+    rmmod $MOD || true
+    exit_fail
+}
+
+unsup() { #msg
+    reset_tracer
+    rmmod $MOD || true
+    echo $1
+    exit_unsupported
+}
+
+modprobe $MOD || unsup "$MOD module not available"
+rmmod $MOD
+
+grep -q "preemptoff" available_tracers || unsup "preemptoff tracer not enabled"
+grep -q "irqsoff" available_tracers || unsup "irqsoff tracer not enabled"
+
+reset_tracer
+
+# Simulate preemptoff section for half a second couple of times
+echo preemptoff > current_tracer
+sleep 1
+modprobe test_atomic_sections atomic_mode=preempt atomic_time=500000 || fail
+rmmod test_atomic_sections || fail
+modprobe test_atomic_sections atomic_mode=preempt atomic_time=500000 || fail
+rmmod test_atomic_sections || fail
+modprobe test_atomic_sections atomic_mode=preempt atomic_time=500000 || fail
+rmmod test_atomic_sections || fail
+
+cat trace
+
+# Confirm which tracer
+grep -q "tracer: preemptoff" trace || fail
+
+# Check the end of the section
+egrep -q "5.....us : <stack trace>" trace || fail
+
+# Check for 500ms of latency
+egrep -q "latency: 5..... us" trace || fail
+
+reset_tracer
+
+# Simulate irqsoff section for half a second couple of times
+echo irqsoff > current_tracer
+sleep 1
+modprobe test_atomic_sections atomic_mode=irq atomic_time=500000 || fail
+rmmod test_atomic_sections || fail
+modprobe test_atomic_sections atomic_mode=irq atomic_time=500000 || fail
+rmmod test_atomic_sections || fail
+modprobe test_atomic_sections atomic_mode=irq atomic_time=500000 || fail
+rmmod test_atomic_sections || fail
+
+cat trace
+
+# Confirm which tracer
+grep -q "tracer: irqsoff" trace || fail
+
+# Check the end of the section
+egrep -q "5.....us : <stack trace>" trace || fail
+
+# Check for 500ms of latency
+egrep -q "latency: 5..... us" trace || fail
+
+reset_tracer
+exit 0
+
-- 
2.17.0.441.gb46fe60e1d-goog

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^ permalink raw reply	[flat|nested] 33+ messages in thread

* [PATCH v7 8/8] kselftests: Add tests for the preemptoff and irqsoff tracers
@ 2018-05-24  1:21   ` joelaf
  0 siblings, 0 replies; 33+ messages in thread
From: Joel Fernandes @ 2018-05-24  1:21 UTC (permalink / raw)


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

Here we add unit tests for the preemptoff and irqsoff tracer by using a
kernel module introduced previously to trigger atomic sections in the
kernel.

Signed-off-by: Joel Fernandes (Google) <joel at joelfernandes.org>
---
 tools/testing/selftests/ftrace/config         |  3 +
 .../test.d/preemptirq/irqsoff_tracer.tc       | 74 +++++++++++++++++++
 2 files changed, 77 insertions(+)
 create mode 100644 tools/testing/selftests/ftrace/test.d/preemptirq/irqsoff_tracer.tc

diff --git a/tools/testing/selftests/ftrace/config b/tools/testing/selftests/ftrace/config
index b01924c71c09..29588b328345 100644
--- a/tools/testing/selftests/ftrace/config
+++ b/tools/testing/selftests/ftrace/config
@@ -4,3 +4,6 @@ CONFIG_FUNCTION_PROFILER=y
 CONFIG_TRACER_SNAPSHOT=y
 CONFIG_STACK_TRACER=y
 CONFIG_HIST_TRIGGERS=y
+CONFIG_PREEMPT_TRACER=y
+CONFIG_IRQSOFF_TRACER=y
+CONFIG_TEST_ATOMIC_SECTIONS=m
diff --git a/tools/testing/selftests/ftrace/test.d/preemptirq/irqsoff_tracer.tc b/tools/testing/selftests/ftrace/test.d/preemptirq/irqsoff_tracer.tc
new file mode 100644
index 000000000000..1764ff22c02b
--- /dev/null
+++ b/tools/testing/selftests/ftrace/test.d/preemptirq/irqsoff_tracer.tc
@@ -0,0 +1,74 @@
+#!/bin/sh
+# SPDX-License-Identifier: GPL-2.0
+# description: test for the preemptirqsoff tracer
+
+MOD=test_atomic_sections
+
+fail() {
+    reset_tracer
+    rmmod $MOD || true
+    exit_fail
+}
+
+unsup() { #msg
+    reset_tracer
+    rmmod $MOD || true
+    echo $1
+    exit_unsupported
+}
+
+modprobe $MOD || unsup "$MOD module not available"
+rmmod $MOD
+
+grep -q "preemptoff" available_tracers || unsup "preemptoff tracer not enabled"
+grep -q "irqsoff" available_tracers || unsup "irqsoff tracer not enabled"
+
+reset_tracer
+
+# Simulate preemptoff section for half a second couple of times
+echo preemptoff > current_tracer
+sleep 1
+modprobe test_atomic_sections atomic_mode=preempt atomic_time=500000 || fail
+rmmod test_atomic_sections || fail
+modprobe test_atomic_sections atomic_mode=preempt atomic_time=500000 || fail
+rmmod test_atomic_sections || fail
+modprobe test_atomic_sections atomic_mode=preempt atomic_time=500000 || fail
+rmmod test_atomic_sections || fail
+
+cat trace
+
+# Confirm which tracer
+grep -q "tracer: preemptoff" trace || fail
+
+# Check the end of the section
+egrep -q "5.....us : <stack trace>" trace || fail
+
+# Check for 500ms of latency
+egrep -q "latency: 5..... us" trace || fail
+
+reset_tracer
+
+# Simulate irqsoff section for half a second couple of times
+echo irqsoff > current_tracer
+sleep 1
+modprobe test_atomic_sections atomic_mode=irq atomic_time=500000 || fail
+rmmod test_atomic_sections || fail
+modprobe test_atomic_sections atomic_mode=irq atomic_time=500000 || fail
+rmmod test_atomic_sections || fail
+modprobe test_atomic_sections atomic_mode=irq atomic_time=500000 || fail
+rmmod test_atomic_sections || fail
+
+cat trace
+
+# Confirm which tracer
+grep -q "tracer: irqsoff" trace || fail
+
+# Check the end of the section
+egrep -q "5.....us : <stack trace>" trace || fail
+
+# Check for 500ms of latency
+egrep -q "latency: 5..... us" trace || fail
+
+reset_tracer
+exit 0
+
-- 
2.17.0.441.gb46fe60e1d-goog

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^ permalink raw reply	[flat|nested] 33+ messages in thread

* Re: [PATCH v7 6/8] tracing: Centralize preemptirq tracepoints and unify their usage
  2018-05-24  1:21   ` joelaf
  (?)
@ 2018-05-25 11:43     ` namhyung
  -1 siblings, 0 replies; 33+ messages in thread
From: Namhyung Kim @ 2018-05-25 11:43 UTC (permalink / raw)
  To: Joel Fernandes
  Cc: linux-kernel, kernel-team, Joel Fernandes (Google),
	Boqun Feng, Byungchul Park, Erick Reyes, Ingo Molnar,
	Julia Cartwright, linux-kselftest, Masami Hiramatsu,
	Mathieu Desnoyers, Paul McKenney, Peter Zijlstra, Shuah Khan,
	Steven Rostedt, Thomas Glexiner, Todd Kjos, Tom Zanussi,
	kernel-team

Hi Joel,

On Wed, May 23, 2018 at 06:21:55PM -0700, Joel Fernandes wrote:
> From: "Joel Fernandes (Google)" <joel@joelfernandes.org>
> 
> This patch detaches the preemptirq tracepoints from the tracers and
> keeps it separate.
> 
> Advantages:
> * Lockdep and irqsoff event can now run in parallel since they no longer
> have their own calls.
> 
> * This unifies the usecase of adding hooks to an irqsoff and irqson
> event, and a preemptoff and preempton event.
>   3 users of the events exist:
>   - Lockdep
>   - irqsoff and preemptoff tracers
>   - irqs and preempt trace events
> 
> The unification cleans up several ifdefs and makes the code in preempt
> tracer and irqsoff tracers simpler. It gets rid of all the horrific
> ifdeferry around PROVE_LOCKING and makes configuration of the different
> users of the tracepoints more easy and understandable. It also gets rid
> of the time_* function calls from the lockdep hooks used to call into
> the preemptirq tracer which is not needed anymore. The negative delta in
> lines of code in this patch is quite large too.
> 
> In the patch we introduce a new CONFIG option PREEMPTIRQ_TRACEPOINTS
> as a single point for registering probes onto the tracepoints. With
> this,
> the web of config options for preempt/irq toggle tracepoints and its
> users becomes:
> 
>  PREEMPT_TRACER   PREEMPTIRQ_EVENTS  IRQSOFF_TRACER PROVE_LOCKING
>        |                 |     \         |           |
>        \    (selects)    /      \        \ (selects) /
>       TRACE_PREEMPT_TOGGLE       ----> TRACE_IRQFLAGS
>                       \                  /
>                        \ (depends on)   /
>                      PREEMPTIRQ_TRACEPOINTS
> 
> One note, I have to check for lockdep recursion in the code that calls
> the trace events API and bail out if we're in lockdep recursion
> protection to prevent something like the following case: a spin_lock is
> taken. Then lockdep_acquired is called.  That does a raw_local_irq_save
> and then sets lockdep_recursion, and then calls __lockdep_acquired. In
> this function, a call to get_lock_stats happens which calls
> preempt_disable, which calls trace IRQS off somewhere which enters my
> tracepoint code and sets the tracing_irq_cpu flag to prevent recursion.
> This flag is then never cleared causing lockdep paths to never be
> entered and thus causing splats and other bad things.
> 
> Other than the performance tests mentioned in the previous patch, I also
> ran the locking API test suite. I verified that all tests cases are
> passing.
> 
> I also injected issues by not registering lockdep probes onto the
> tracepoints and I see failures to confirm that the probes are indeed
> working.
> 
> Without probes:
> 
> [    0.000000]      hard-irqs-on + irq-safe-A/21:  ok  |  ok  |  ok  |
> [    0.000000]      soft-irqs-on + irq-safe-A/21:  ok  |  ok  |  ok  |
> [    0.000000]        sirq-safe-A => hirqs-on/12:  ok  |  ok  |  ok  |
> [    0.000000]        sirq-safe-A => hirqs-on/21:  ok  |  ok  |  ok  |
> [    0.000000]          hard-safe-A + irqs-on/12:  ok  |  ok  |  ok  |
> [    0.000000]          soft-safe-A + irqs-on/12:  ok  |  ok  |  ok  |
> [    0.000000]          hard-safe-A + irqs-on/21:  ok  |  ok  |  ok  |
> [    0.000000]          soft-safe-A + irqs-on/21:  ok  |  ok  |  ok  |
> [    0.000000]     hard-safe-A + unsafe-B #1/123:  ok  |  ok  |  ok  |
> [    0.000000]     soft-safe-A + unsafe-B #1/123:  ok  |  ok  |  ok  |
> 
> With probes:
> 
> [    0.000000]      hard-irqs-on + irq-safe-A/21:  ok  |  ok  |  ok  |
> [    0.000000]      soft-irqs-on + irq-safe-A/21:  ok  |  ok  |  ok  |
> [    0.000000]        sirq-safe-A => hirqs-on/12:FAILED|FAILED|  ok  |
> [    0.000000]        sirq-safe-A => hirqs-on/21:FAILED|FAILED|  ok  |
> [    0.000000]          hard-safe-A + irqs-on/12:FAILED|FAILED|  ok  |
> [    0.000000]          soft-safe-A + irqs-on/12:FAILED|FAILED|  ok  |
> [    0.000000]          hard-safe-A + irqs-on/21:FAILED|FAILED|  ok  |
> [    0.000000]          soft-safe-A + irqs-on/21:FAILED|FAILED|  ok  |
> [    0.000000]     hard-safe-A + unsafe-B #1/123:  ok  |  ok  |  ok  |
> [    0.000000]     soft-safe-A + unsafe-B #1/123:  ok  |  ok  |  ok  |
> 
> Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
> ---

[SNIP]
>  
>  #ifdef CONFIG_IRQSOFF_TRACER
> +/*
> + * We are only interested in hardirq on/off events:
> + */
> +static void tracer_hardirqs_on(void *none, unsigned long a0, unsigned long a1)
> +{
> +	if (!preempt_trace() && irq_trace())
> +		stop_critical_timing(a0, a1);
> +}
> +
> +static void tracer_hardirqs_off(void *none, unsigned long a0, unsigned long a1)
> +{
> +	if (!preempt_trace() && irq_trace())
> +		start_critical_timing(a0, a1);
> +}
> +
>  static int irqsoff_tracer_init(struct trace_array *tr)
>  {
>  	trace_type = TRACER_IRQS_OFF;
>  
> +	register_trace_irq_disable(tracer_hardirqs_off, NULL);
> +	register_trace_irq_enable(tracer_hardirqs_on, NULL);
>  	return __irqsoff_tracer_init(tr);
>  }
>  
>  static void irqsoff_tracer_reset(struct trace_array *tr)
>  {
> +	unregister_trace_irq_disable(tracer_hardirqs_off, NULL);
> +	unregister_trace_irq_enable(tracer_hardirqs_on, NULL);
>  	__irqsoff_tracer_reset(tr);
>  }
>  
> @@ -692,19 +650,37 @@ static struct tracer irqsoff_tracer __read_mostly =
>  };
>  # define register_irqsoff(trace) register_tracer(&trace)
>  #else
> +static inline void tracer_hardirqs_on(unsigned long a0, unsigned long a1) { }
> +static inline void tracer_hardirqs_off(unsigned long a0, unsigned long a1) { }

Just a nitpick.  These lines seem unnecessary since they're used
only when CONFIG_IRQSOFF_TRACER is enabled AFAICS.


>  # define register_irqsoff(trace) do { } while (0)
> -#endif
> +#endif /*  CONFIG_IRQSOFF_TRACER */
>  
>  #ifdef CONFIG_PREEMPT_TRACER
> +static void tracer_preempt_on(void *none, unsigned long a0, unsigned long a1)
> +{
> +	if (preempt_trace() && !irq_trace())
> +		stop_critical_timing(a0, a1);
> +}
> +
> +static void tracer_preempt_off(void *none, unsigned long a0, unsigned long a1)
> +{
> +	if (preempt_trace() && !irq_trace())
> +		start_critical_timing(a0, a1);
> +}
> +
>  static int preemptoff_tracer_init(struct trace_array *tr)
>  {
>  	trace_type = TRACER_PREEMPT_OFF;
>  
> +	register_trace_preempt_disable(tracer_preempt_off, NULL);
> +	register_trace_preempt_enable(tracer_preempt_on, NULL);
>  	return __irqsoff_tracer_init(tr);
>  }
>  
>  static void preemptoff_tracer_reset(struct trace_array *tr)
>  {
> +	unregister_trace_preempt_disable(tracer_preempt_off, NULL);
> +	unregister_trace_preempt_enable(tracer_preempt_on, NULL);
>  	__irqsoff_tracer_reset(tr);
>  }
>  
> @@ -729,21 +705,32 @@ static struct tracer preemptoff_tracer __read_mostly =
>  };
>  # define register_preemptoff(trace) register_tracer(&trace)
>  #else
> +static inline void tracer_preempt_on(unsigned long a0, unsigned long a1) { }
> +static inline void tracer_preempt_off(unsigned long a0, unsigned long a1) { }

Ditto (for CONFIG_PREEMPT_TRACER).

Thanks,
Namhyung


>  # define register_preemptoff(trace) do { } while (0)
> -#endif
> +#endif /* CONFIG_PREEMPT_TRACER */
>  
> -#if defined(CONFIG_IRQSOFF_TRACER) && \
> -	defined(CONFIG_PREEMPT_TRACER)
> +#if defined(CONFIG_IRQSOFF_TRACER) && defined(CONFIG_PREEMPT_TRACER)
>  
>  static int preemptirqsoff_tracer_init(struct trace_array *tr)
>  {
>  	trace_type = TRACER_IRQS_OFF | TRACER_PREEMPT_OFF;
>  
> +	register_trace_irq_disable(tracer_hardirqs_off, NULL);
> +	register_trace_irq_enable(tracer_hardirqs_on, NULL);
> +	register_trace_preempt_disable(tracer_preempt_off, NULL);
> +	register_trace_preempt_enable(tracer_preempt_on, NULL);
> +
>  	return __irqsoff_tracer_init(tr);
>  }
>  
>  static void preemptirqsoff_tracer_reset(struct trace_array *tr)
>  {
> +	unregister_trace_irq_disable(tracer_hardirqs_off, NULL);
> +	unregister_trace_irq_enable(tracer_hardirqs_on, NULL);
> +	unregister_trace_preempt_disable(tracer_preempt_off, NULL);
> +	unregister_trace_preempt_enable(tracer_preempt_on, NULL);
> +
>  	__irqsoff_tracer_reset(tr);
>  }

^ permalink raw reply	[flat|nested] 33+ messages in thread

* [PATCH v7 6/8] tracing: Centralize preemptirq tracepoints and unify their usage
@ 2018-05-25 11:43     ` namhyung
  0 siblings, 0 replies; 33+ messages in thread
From: namhyung @ 2018-05-25 11:43 UTC (permalink / raw)


Hi Joel,

On Wed, May 23, 2018 at 06:21:55PM -0700, Joel Fernandes wrote:
> From: "Joel Fernandes (Google)" <joel at joelfernandes.org>
> 
> This patch detaches the preemptirq tracepoints from the tracers and
> keeps it separate.
> 
> Advantages:
> * Lockdep and irqsoff event can now run in parallel since they no longer
> have their own calls.
> 
> * This unifies the usecase of adding hooks to an irqsoff and irqson
> event, and a preemptoff and preempton event.
>   3 users of the events exist:
>   - Lockdep
>   - irqsoff and preemptoff tracers
>   - irqs and preempt trace events
> 
> The unification cleans up several ifdefs and makes the code in preempt
> tracer and irqsoff tracers simpler. It gets rid of all the horrific
> ifdeferry around PROVE_LOCKING and makes configuration of the different
> users of the tracepoints more easy and understandable. It also gets rid
> of the time_* function calls from the lockdep hooks used to call into
> the preemptirq tracer which is not needed anymore. The negative delta in
> lines of code in this patch is quite large too.
> 
> In the patch we introduce a new CONFIG option PREEMPTIRQ_TRACEPOINTS
> as a single point for registering probes onto the tracepoints. With
> this,
> the web of config options for preempt/irq toggle tracepoints and its
> users becomes:
> 
>  PREEMPT_TRACER   PREEMPTIRQ_EVENTS  IRQSOFF_TRACER PROVE_LOCKING
>        |                 |     \         |           |
>        \    (selects)    /      \        \ (selects) /
>       TRACE_PREEMPT_TOGGLE       ----> TRACE_IRQFLAGS
>                       \                  /
>                        \ (depends on)   /
>                      PREEMPTIRQ_TRACEPOINTS
> 
> One note, I have to check for lockdep recursion in the code that calls
> the trace events API and bail out if we're in lockdep recursion
> protection to prevent something like the following case: a spin_lock is
> taken. Then lockdep_acquired is called.  That does a raw_local_irq_save
> and then sets lockdep_recursion, and then calls __lockdep_acquired. In
> this function, a call to get_lock_stats happens which calls
> preempt_disable, which calls trace IRQS off somewhere which enters my
> tracepoint code and sets the tracing_irq_cpu flag to prevent recursion.
> This flag is then never cleared causing lockdep paths to never be
> entered and thus causing splats and other bad things.
> 
> Other than the performance tests mentioned in the previous patch, I also
> ran the locking API test suite. I verified that all tests cases are
> passing.
> 
> I also injected issues by not registering lockdep probes onto the
> tracepoints and I see failures to confirm that the probes are indeed
> working.
> 
> Without probes:
> 
> [    0.000000]      hard-irqs-on + irq-safe-A/21:  ok  |  ok  |  ok  |
> [    0.000000]      soft-irqs-on + irq-safe-A/21:  ok  |  ok  |  ok  |
> [    0.000000]        sirq-safe-A => hirqs-on/12:  ok  |  ok  |  ok  |
> [    0.000000]        sirq-safe-A => hirqs-on/21:  ok  |  ok  |  ok  |
> [    0.000000]          hard-safe-A + irqs-on/12:  ok  |  ok  |  ok  |
> [    0.000000]          soft-safe-A + irqs-on/12:  ok  |  ok  |  ok  |
> [    0.000000]          hard-safe-A + irqs-on/21:  ok  |  ok  |  ok  |
> [    0.000000]          soft-safe-A + irqs-on/21:  ok  |  ok  |  ok  |
> [    0.000000]     hard-safe-A + unsafe-B #1/123:  ok  |  ok  |  ok  |
> [    0.000000]     soft-safe-A + unsafe-B #1/123:  ok  |  ok  |  ok  |
> 
> With probes:
> 
> [    0.000000]      hard-irqs-on + irq-safe-A/21:  ok  |  ok  |  ok  |
> [    0.000000]      soft-irqs-on + irq-safe-A/21:  ok  |  ok  |  ok  |
> [    0.000000]        sirq-safe-A => hirqs-on/12:FAILED|FAILED|  ok  |
> [    0.000000]        sirq-safe-A => hirqs-on/21:FAILED|FAILED|  ok  |
> [    0.000000]          hard-safe-A + irqs-on/12:FAILED|FAILED|  ok  |
> [    0.000000]          soft-safe-A + irqs-on/12:FAILED|FAILED|  ok  |
> [    0.000000]          hard-safe-A + irqs-on/21:FAILED|FAILED|  ok  |
> [    0.000000]          soft-safe-A + irqs-on/21:FAILED|FAILED|  ok  |
> [    0.000000]     hard-safe-A + unsafe-B #1/123:  ok  |  ok  |  ok  |
> [    0.000000]     soft-safe-A + unsafe-B #1/123:  ok  |  ok  |  ok  |
> 
> Signed-off-by: Joel Fernandes (Google) <joel at joelfernandes.org>
> ---

[SNIP]
>  
>  #ifdef CONFIG_IRQSOFF_TRACER
> +/*
> + * We are only interested in hardirq on/off events:
> + */
> +static void tracer_hardirqs_on(void *none, unsigned long a0, unsigned long a1)
> +{
> +	if (!preempt_trace() && irq_trace())
> +		stop_critical_timing(a0, a1);
> +}
> +
> +static void tracer_hardirqs_off(void *none, unsigned long a0, unsigned long a1)
> +{
> +	if (!preempt_trace() && irq_trace())
> +		start_critical_timing(a0, a1);
> +}
> +
>  static int irqsoff_tracer_init(struct trace_array *tr)
>  {
>  	trace_type = TRACER_IRQS_OFF;
>  
> +	register_trace_irq_disable(tracer_hardirqs_off, NULL);
> +	register_trace_irq_enable(tracer_hardirqs_on, NULL);
>  	return __irqsoff_tracer_init(tr);
>  }
>  
>  static void irqsoff_tracer_reset(struct trace_array *tr)
>  {
> +	unregister_trace_irq_disable(tracer_hardirqs_off, NULL);
> +	unregister_trace_irq_enable(tracer_hardirqs_on, NULL);
>  	__irqsoff_tracer_reset(tr);
>  }
>  
> @@ -692,19 +650,37 @@ static struct tracer irqsoff_tracer __read_mostly =
>  };
>  # define register_irqsoff(trace) register_tracer(&trace)
>  #else
> +static inline void tracer_hardirqs_on(unsigned long a0, unsigned long a1) { }
> +static inline void tracer_hardirqs_off(unsigned long a0, unsigned long a1) { }

Just a nitpick.  These lines seem unnecessary since they're used
only when CONFIG_IRQSOFF_TRACER is enabled AFAICS.


>  # define register_irqsoff(trace) do { } while (0)
> -#endif
> +#endif /*  CONFIG_IRQSOFF_TRACER */
>  
>  #ifdef CONFIG_PREEMPT_TRACER
> +static void tracer_preempt_on(void *none, unsigned long a0, unsigned long a1)
> +{
> +	if (preempt_trace() && !irq_trace())
> +		stop_critical_timing(a0, a1);
> +}
> +
> +static void tracer_preempt_off(void *none, unsigned long a0, unsigned long a1)
> +{
> +	if (preempt_trace() && !irq_trace())
> +		start_critical_timing(a0, a1);
> +}
> +
>  static int preemptoff_tracer_init(struct trace_array *tr)
>  {
>  	trace_type = TRACER_PREEMPT_OFF;
>  
> +	register_trace_preempt_disable(tracer_preempt_off, NULL);
> +	register_trace_preempt_enable(tracer_preempt_on, NULL);
>  	return __irqsoff_tracer_init(tr);
>  }
>  
>  static void preemptoff_tracer_reset(struct trace_array *tr)
>  {
> +	unregister_trace_preempt_disable(tracer_preempt_off, NULL);
> +	unregister_trace_preempt_enable(tracer_preempt_on, NULL);
>  	__irqsoff_tracer_reset(tr);
>  }
>  
> @@ -729,21 +705,32 @@ static struct tracer preemptoff_tracer __read_mostly =
>  };
>  # define register_preemptoff(trace) register_tracer(&trace)
>  #else
> +static inline void tracer_preempt_on(unsigned long a0, unsigned long a1) { }
> +static inline void tracer_preempt_off(unsigned long a0, unsigned long a1) { }

Ditto (for CONFIG_PREEMPT_TRACER).

Thanks,
Namhyung


>  # define register_preemptoff(trace) do { } while (0)
> -#endif
> +#endif /* CONFIG_PREEMPT_TRACER */
>  
> -#if defined(CONFIG_IRQSOFF_TRACER) && \
> -	defined(CONFIG_PREEMPT_TRACER)
> +#if defined(CONFIG_IRQSOFF_TRACER) && defined(CONFIG_PREEMPT_TRACER)
>  
>  static int preemptirqsoff_tracer_init(struct trace_array *tr)
>  {
>  	trace_type = TRACER_IRQS_OFF | TRACER_PREEMPT_OFF;
>  
> +	register_trace_irq_disable(tracer_hardirqs_off, NULL);
> +	register_trace_irq_enable(tracer_hardirqs_on, NULL);
> +	register_trace_preempt_disable(tracer_preempt_off, NULL);
> +	register_trace_preempt_enable(tracer_preempt_on, NULL);
> +
>  	return __irqsoff_tracer_init(tr);
>  }
>  
>  static void preemptirqsoff_tracer_reset(struct trace_array *tr)
>  {
> +	unregister_trace_irq_disable(tracer_hardirqs_off, NULL);
> +	unregister_trace_irq_enable(tracer_hardirqs_on, NULL);
> +	unregister_trace_preempt_disable(tracer_preempt_off, NULL);
> +	unregister_trace_preempt_enable(tracer_preempt_on, NULL);
> +
>  	__irqsoff_tracer_reset(tr);
>  }
--
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^ permalink raw reply	[flat|nested] 33+ messages in thread

* [PATCH v7 6/8] tracing: Centralize preemptirq tracepoints and unify their usage
@ 2018-05-25 11:43     ` namhyung
  0 siblings, 0 replies; 33+ messages in thread
From: Namhyung Kim @ 2018-05-25 11:43 UTC (permalink / raw)


Hi Joel,

On Wed, May 23, 2018@06:21:55PM -0700, Joel Fernandes wrote:
> From: "Joel Fernandes (Google)" <joel at joelfernandes.org>
> 
> This patch detaches the preemptirq tracepoints from the tracers and
> keeps it separate.
> 
> Advantages:
> * Lockdep and irqsoff event can now run in parallel since they no longer
> have their own calls.
> 
> * This unifies the usecase of adding hooks to an irqsoff and irqson
> event, and a preemptoff and preempton event.
>   3 users of the events exist:
>   - Lockdep
>   - irqsoff and preemptoff tracers
>   - irqs and preempt trace events
> 
> The unification cleans up several ifdefs and makes the code in preempt
> tracer and irqsoff tracers simpler. It gets rid of all the horrific
> ifdeferry around PROVE_LOCKING and makes configuration of the different
> users of the tracepoints more easy and understandable. It also gets rid
> of the time_* function calls from the lockdep hooks used to call into
> the preemptirq tracer which is not needed anymore. The negative delta in
> lines of code in this patch is quite large too.
> 
> In the patch we introduce a new CONFIG option PREEMPTIRQ_TRACEPOINTS
> as a single point for registering probes onto the tracepoints. With
> this,
> the web of config options for preempt/irq toggle tracepoints and its
> users becomes:
> 
>  PREEMPT_TRACER   PREEMPTIRQ_EVENTS  IRQSOFF_TRACER PROVE_LOCKING
>        |                 |     \         |           |
>        \    (selects)    /      \        \ (selects) /
>       TRACE_PREEMPT_TOGGLE       ----> TRACE_IRQFLAGS
>                       \                  /
>                        \ (depends on)   /
>                      PREEMPTIRQ_TRACEPOINTS
> 
> One note, I have to check for lockdep recursion in the code that calls
> the trace events API and bail out if we're in lockdep recursion
> protection to prevent something like the following case: a spin_lock is
> taken. Then lockdep_acquired is called.  That does a raw_local_irq_save
> and then sets lockdep_recursion, and then calls __lockdep_acquired. In
> this function, a call to get_lock_stats happens which calls
> preempt_disable, which calls trace IRQS off somewhere which enters my
> tracepoint code and sets the tracing_irq_cpu flag to prevent recursion.
> This flag is then never cleared causing lockdep paths to never be
> entered and thus causing splats and other bad things.
> 
> Other than the performance tests mentioned in the previous patch, I also
> ran the locking API test suite. I verified that all tests cases are
> passing.
> 
> I also injected issues by not registering lockdep probes onto the
> tracepoints and I see failures to confirm that the probes are indeed
> working.
> 
> Without probes:
> 
> [    0.000000]      hard-irqs-on + irq-safe-A/21:  ok  |  ok  |  ok  |
> [    0.000000]      soft-irqs-on + irq-safe-A/21:  ok  |  ok  |  ok  |
> [    0.000000]        sirq-safe-A => hirqs-on/12:  ok  |  ok  |  ok  |
> [    0.000000]        sirq-safe-A => hirqs-on/21:  ok  |  ok  |  ok  |
> [    0.000000]          hard-safe-A + irqs-on/12:  ok  |  ok  |  ok  |
> [    0.000000]          soft-safe-A + irqs-on/12:  ok  |  ok  |  ok  |
> [    0.000000]          hard-safe-A + irqs-on/21:  ok  |  ok  |  ok  |
> [    0.000000]          soft-safe-A + irqs-on/21:  ok  |  ok  |  ok  |
> [    0.000000]     hard-safe-A + unsafe-B #1/123:  ok  |  ok  |  ok  |
> [    0.000000]     soft-safe-A + unsafe-B #1/123:  ok  |  ok  |  ok  |
> 
> With probes:
> 
> [    0.000000]      hard-irqs-on + irq-safe-A/21:  ok  |  ok  |  ok  |
> [    0.000000]      soft-irqs-on + irq-safe-A/21:  ok  |  ok  |  ok  |
> [    0.000000]        sirq-safe-A => hirqs-on/12:FAILED|FAILED|  ok  |
> [    0.000000]        sirq-safe-A => hirqs-on/21:FAILED|FAILED|  ok  |
> [    0.000000]          hard-safe-A + irqs-on/12:FAILED|FAILED|  ok  |
> [    0.000000]          soft-safe-A + irqs-on/12:FAILED|FAILED|  ok  |
> [    0.000000]          hard-safe-A + irqs-on/21:FAILED|FAILED|  ok  |
> [    0.000000]          soft-safe-A + irqs-on/21:FAILED|FAILED|  ok  |
> [    0.000000]     hard-safe-A + unsafe-B #1/123:  ok  |  ok  |  ok  |
> [    0.000000]     soft-safe-A + unsafe-B #1/123:  ok  |  ok  |  ok  |
> 
> Signed-off-by: Joel Fernandes (Google) <joel at joelfernandes.org>
> ---

[SNIP]
>  
>  #ifdef CONFIG_IRQSOFF_TRACER
> +/*
> + * We are only interested in hardirq on/off events:
> + */
> +static void tracer_hardirqs_on(void *none, unsigned long a0, unsigned long a1)
> +{
> +	if (!preempt_trace() && irq_trace())
> +		stop_critical_timing(a0, a1);
> +}
> +
> +static void tracer_hardirqs_off(void *none, unsigned long a0, unsigned long a1)
> +{
> +	if (!preempt_trace() && irq_trace())
> +		start_critical_timing(a0, a1);
> +}
> +
>  static int irqsoff_tracer_init(struct trace_array *tr)
>  {
>  	trace_type = TRACER_IRQS_OFF;
>  
> +	register_trace_irq_disable(tracer_hardirqs_off, NULL);
> +	register_trace_irq_enable(tracer_hardirqs_on, NULL);
>  	return __irqsoff_tracer_init(tr);
>  }
>  
>  static void irqsoff_tracer_reset(struct trace_array *tr)
>  {
> +	unregister_trace_irq_disable(tracer_hardirqs_off, NULL);
> +	unregister_trace_irq_enable(tracer_hardirqs_on, NULL);
>  	__irqsoff_tracer_reset(tr);
>  }
>  
> @@ -692,19 +650,37 @@ static struct tracer irqsoff_tracer __read_mostly =
>  };
>  # define register_irqsoff(trace) register_tracer(&trace)
>  #else
> +static inline void tracer_hardirqs_on(unsigned long a0, unsigned long a1) { }
> +static inline void tracer_hardirqs_off(unsigned long a0, unsigned long a1) { }

Just a nitpick.  These lines seem unnecessary since they're used
only when CONFIG_IRQSOFF_TRACER is enabled AFAICS.


>  # define register_irqsoff(trace) do { } while (0)
> -#endif
> +#endif /*  CONFIG_IRQSOFF_TRACER */
>  
>  #ifdef CONFIG_PREEMPT_TRACER
> +static void tracer_preempt_on(void *none, unsigned long a0, unsigned long a1)
> +{
> +	if (preempt_trace() && !irq_trace())
> +		stop_critical_timing(a0, a1);
> +}
> +
> +static void tracer_preempt_off(void *none, unsigned long a0, unsigned long a1)
> +{
> +	if (preempt_trace() && !irq_trace())
> +		start_critical_timing(a0, a1);
> +}
> +
>  static int preemptoff_tracer_init(struct trace_array *tr)
>  {
>  	trace_type = TRACER_PREEMPT_OFF;
>  
> +	register_trace_preempt_disable(tracer_preempt_off, NULL);
> +	register_trace_preempt_enable(tracer_preempt_on, NULL);
>  	return __irqsoff_tracer_init(tr);
>  }
>  
>  static void preemptoff_tracer_reset(struct trace_array *tr)
>  {
> +	unregister_trace_preempt_disable(tracer_preempt_off, NULL);
> +	unregister_trace_preempt_enable(tracer_preempt_on, NULL);
>  	__irqsoff_tracer_reset(tr);
>  }
>  
> @@ -729,21 +705,32 @@ static struct tracer preemptoff_tracer __read_mostly =
>  };
>  # define register_preemptoff(trace) register_tracer(&trace)
>  #else
> +static inline void tracer_preempt_on(unsigned long a0, unsigned long a1) { }
> +static inline void tracer_preempt_off(unsigned long a0, unsigned long a1) { }

Ditto (for CONFIG_PREEMPT_TRACER).

Thanks,
Namhyung


>  # define register_preemptoff(trace) do { } while (0)
> -#endif
> +#endif /* CONFIG_PREEMPT_TRACER */
>  
> -#if defined(CONFIG_IRQSOFF_TRACER) && \
> -	defined(CONFIG_PREEMPT_TRACER)
> +#if defined(CONFIG_IRQSOFF_TRACER) && defined(CONFIG_PREEMPT_TRACER)
>  
>  static int preemptirqsoff_tracer_init(struct trace_array *tr)
>  {
>  	trace_type = TRACER_IRQS_OFF | TRACER_PREEMPT_OFF;
>  
> +	register_trace_irq_disable(tracer_hardirqs_off, NULL);
> +	register_trace_irq_enable(tracer_hardirqs_on, NULL);
> +	register_trace_preempt_disable(tracer_preempt_off, NULL);
> +	register_trace_preempt_enable(tracer_preempt_on, NULL);
> +
>  	return __irqsoff_tracer_init(tr);
>  }
>  
>  static void preemptirqsoff_tracer_reset(struct trace_array *tr)
>  {
> +	unregister_trace_irq_disable(tracer_hardirqs_off, NULL);
> +	unregister_trace_irq_enable(tracer_hardirqs_on, NULL);
> +	unregister_trace_preempt_disable(tracer_preempt_off, NULL);
> +	unregister_trace_preempt_enable(tracer_preempt_on, NULL);
> +
>  	__irqsoff_tracer_reset(tr);
>  }
--
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^ permalink raw reply	[flat|nested] 33+ messages in thread

* Re: [PATCH v7 6/8] tracing: Centralize preemptirq tracepoints and unify their usage
  2018-05-25 11:43     ` namhyung
  (?)
@ 2018-05-25 23:20       ` joel
  -1 siblings, 0 replies; 33+ messages in thread
From: Joel Fernandes @ 2018-05-25 23:20 UTC (permalink / raw)
  To: Namhyung Kim
  Cc: Joel Fernandes, linux-kernel, kernel-team, Boqun Feng,
	Byungchul Park, Erick Reyes, Ingo Molnar, Julia Cartwright,
	linux-kselftest, Masami Hiramatsu, Mathieu Desnoyers,
	Paul McKenney, Peter Zijlstra, Shuah Khan, Steven Rostedt,
	Thomas Glexiner, Todd Kjos, Tom Zanussi, kernel-team

On Fri, May 25, 2018 at 08:43:39PM +0900, Namhyung Kim wrote:
> Hi Joel,
> 
> On Wed, May 23, 2018 at 06:21:55PM -0700, Joel Fernandes wrote:
> > From: "Joel Fernandes (Google)" <joel@joelfernandes.org>
> > 
> > This patch detaches the preemptirq tracepoints from the tracers and
> > keeps it separate.
> > 
> > Advantages:
> > * Lockdep and irqsoff event can now run in parallel since they no longer
> > have their own calls.
> > 
> > * This unifies the usecase of adding hooks to an irqsoff and irqson
> > event, and a preemptoff and preempton event.
> >   3 users of the events exist:
> >   - Lockdep
> >   - irqsoff and preemptoff tracers
> >   - irqs and preempt trace events
> > 
> > The unification cleans up several ifdefs and makes the code in preempt
> > tracer and irqsoff tracers simpler. It gets rid of all the horrific
> > ifdeferry around PROVE_LOCKING and makes configuration of the different
> > users of the tracepoints more easy and understandable. It also gets rid
> > of the time_* function calls from the lockdep hooks used to call into
> > the preemptirq tracer which is not needed anymore. The negative delta in
> > lines of code in this patch is quite large too.
> > 
> [SNIP]
> >  
> >  #ifdef CONFIG_IRQSOFF_TRACER
> > +/*
> > + * We are only interested in hardirq on/off events:
> > + */
> > +static void tracer_hardirqs_on(void *none, unsigned long a0, unsigned long a1)
> > +{
> > +	if (!preempt_trace() && irq_trace())
> > +		stop_critical_timing(a0, a1);
> > +}
> > +
> > +static void tracer_hardirqs_off(void *none, unsigned long a0, unsigned long a1)
> > +{
> > +	if (!preempt_trace() && irq_trace())
> > +		start_critical_timing(a0, a1);
> > +}
> > +
> >  static int irqsoff_tracer_init(struct trace_array *tr)
> >  {
> >  	trace_type = TRACER_IRQS_OFF;
> >  
> > +	register_trace_irq_disable(tracer_hardirqs_off, NULL);
> > +	register_trace_irq_enable(tracer_hardirqs_on, NULL);
> >  	return __irqsoff_tracer_init(tr);
> >  }
> >  
> >  static void irqsoff_tracer_reset(struct trace_array *tr)
> >  {
> > +	unregister_trace_irq_disable(tracer_hardirqs_off, NULL);
> > +	unregister_trace_irq_enable(tracer_hardirqs_on, NULL);
> >  	__irqsoff_tracer_reset(tr);
> >  }
> >  
> > @@ -692,19 +650,37 @@ static struct tracer irqsoff_tracer __read_mostly =
> >  };
> >  # define register_irqsoff(trace) register_tracer(&trace)
> >  #else
> > +static inline void tracer_hardirqs_on(unsigned long a0, unsigned long a1) { }
> > +static inline void tracer_hardirqs_off(unsigned long a0, unsigned long a1) { }
> 
> Just a nitpick.  These lines seem unnecessary since they're used
> only when CONFIG_IRQSOFF_TRACER is enabled AFAICS.
> 
> 
> >  # define register_irqsoff(trace) do { } while (0)
> > -#endif
> > +#endif /*  CONFIG_IRQSOFF_TRACER */
> >  
> >  #ifdef CONFIG_PREEMPT_TRACER
> > +static void tracer_preempt_on(void *none, unsigned long a0, unsigned long a1)
> > +{
> > +	if (preempt_trace() && !irq_trace())
> > +		stop_critical_timing(a0, a1);
> > +}
> > +
> > +static void tracer_preempt_off(void *none, unsigned long a0, unsigned long a1)
> > +{
> > +	if (preempt_trace() && !irq_trace())
> > +		start_critical_timing(a0, a1);
> > +}
> > +
> >  static int preemptoff_tracer_init(struct trace_array *tr)
> >  {
> >  	trace_type = TRACER_PREEMPT_OFF;
> >  
> > +	register_trace_preempt_disable(tracer_preempt_off, NULL);
> > +	register_trace_preempt_enable(tracer_preempt_on, NULL);
> >  	return __irqsoff_tracer_init(tr);
> >  }
> >  
> >  static void preemptoff_tracer_reset(struct trace_array *tr)
> >  {
> > +	unregister_trace_preempt_disable(tracer_preempt_off, NULL);
> > +	unregister_trace_preempt_enable(tracer_preempt_on, NULL);
> >  	__irqsoff_tracer_reset(tr);
> >  }
> >  
> > @@ -729,21 +705,32 @@ static struct tracer preemptoff_tracer __read_mostly =
> >  };
> >  # define register_preemptoff(trace) register_tracer(&trace)
> >  #else
> > +static inline void tracer_preempt_on(unsigned long a0, unsigned long a1) { }
> > +static inline void tracer_preempt_off(unsigned long a0, unsigned long a1) { }
> 
> Ditto (for CONFIG_PREEMPT_TRACER).
> 
> Thanks,
> Namhyung

Yes you're right, saves quite a few lines actually! I also inlined the
register_tracer macros, It seems much cleaner. I will fold the below diff but
let me know if there's anything else.

Thanks Namhyung!

 - Joel


---8<-----------------------

diff --git a/kernel/trace/trace_irqsoff.c b/kernel/trace/trace_irqsoff.c
index d2d8284088f0..d0bcb51d1a2a 100644
--- a/kernel/trace/trace_irqsoff.c
+++ b/kernel/trace/trace_irqsoff.c
@@ -648,11 +648,6 @@ static struct tracer irqsoff_tracer __read_mostly =
 	.allow_instances = true,
 	.use_max_tr	= true,
 };
-# define register_irqsoff(trace) register_tracer(&trace)
-#else
-static inline void tracer_hardirqs_on(unsigned long a0, unsigned long a1) { }
-static inline void tracer_hardirqs_off(unsigned long a0, unsigned long a1) { }
-# define register_irqsoff(trace) do { } while (0)
 #endif /*  CONFIG_IRQSOFF_TRACER */
 
 #ifdef CONFIG_PREEMPT_TRACER
@@ -703,11 +698,6 @@ static struct tracer preemptoff_tracer __read_mostly =
 	.allow_instances = true,
 	.use_max_tr	= true,
 };
-# define register_preemptoff(trace) register_tracer(&trace)
-#else
-static inline void tracer_preempt_on(unsigned long a0, unsigned long a1) { }
-static inline void tracer_preempt_off(unsigned long a0, unsigned long a1) { }
-# define register_preemptoff(trace) do { } while (0)
 #endif /* CONFIG_PREEMPT_TRACER */
 
 #if defined(CONFIG_IRQSOFF_TRACER) && defined(CONFIG_PREEMPT_TRACER)
@@ -753,18 +743,19 @@ static struct tracer preemptirqsoff_tracer __read_mostly =
 	.allow_instances = true,
 	.use_max_tr	= true,
 };
-
-# define register_preemptirqsoff(trace) register_tracer(&trace)
-#else
-# define register_preemptirqsoff(trace) do { } while (0)
 #endif
 
 __init static int init_irqsoff_tracer(void)
 {
-	register_irqsoff(irqsoff_tracer);
-	register_preemptoff(preemptoff_tracer);
-	register_preemptirqsoff(preemptirqsoff_tracer);
-
+#ifdef CONFIG_IRQSOFF_TRACER
+	register_tracer(&irqsoff_tracer);
+#endif
+#ifdef CONFIG_PREEMPT_TRACER
+	register_tracer(&preemptoff_tracer);
+#endif
+#if defined(CONFIG_IRQSOFF_TRACER) && defined(CONFIG_PREEMPT_TRACER)
+	register_tracer(&preemptirqsoff_tracer);
+#endif
 	return 0;
 }
 core_initcall(init_irqsoff_tracer);

^ permalink raw reply	[flat|nested] 33+ messages in thread

* [PATCH v7 6/8] tracing: Centralize preemptirq tracepoints and unify their usage
@ 2018-05-25 23:20       ` joel
  0 siblings, 0 replies; 33+ messages in thread
From: joel @ 2018-05-25 23:20 UTC (permalink / raw)


On Fri, May 25, 2018 at 08:43:39PM +0900, Namhyung Kim wrote:
> Hi Joel,
> 
> On Wed, May 23, 2018 at 06:21:55PM -0700, Joel Fernandes wrote:
> > From: "Joel Fernandes (Google)" <joel at joelfernandes.org>
> > 
> > This patch detaches the preemptirq tracepoints from the tracers and
> > keeps it separate.
> > 
> > Advantages:
> > * Lockdep and irqsoff event can now run in parallel since they no longer
> > have their own calls.
> > 
> > * This unifies the usecase of adding hooks to an irqsoff and irqson
> > event, and a preemptoff and preempton event.
> >   3 users of the events exist:
> >   - Lockdep
> >   - irqsoff and preemptoff tracers
> >   - irqs and preempt trace events
> > 
> > The unification cleans up several ifdefs and makes the code in preempt
> > tracer and irqsoff tracers simpler. It gets rid of all the horrific
> > ifdeferry around PROVE_LOCKING and makes configuration of the different
> > users of the tracepoints more easy and understandable. It also gets rid
> > of the time_* function calls from the lockdep hooks used to call into
> > the preemptirq tracer which is not needed anymore. The negative delta in
> > lines of code in this patch is quite large too.
> > 
> [SNIP]
> >  
> >  #ifdef CONFIG_IRQSOFF_TRACER
> > +/*
> > + * We are only interested in hardirq on/off events:
> > + */
> > +static void tracer_hardirqs_on(void *none, unsigned long a0, unsigned long a1)
> > +{
> > +	if (!preempt_trace() && irq_trace())
> > +		stop_critical_timing(a0, a1);
> > +}
> > +
> > +static void tracer_hardirqs_off(void *none, unsigned long a0, unsigned long a1)
> > +{
> > +	if (!preempt_trace() && irq_trace())
> > +		start_critical_timing(a0, a1);
> > +}
> > +
> >  static int irqsoff_tracer_init(struct trace_array *tr)
> >  {
> >  	trace_type = TRACER_IRQS_OFF;
> >  
> > +	register_trace_irq_disable(tracer_hardirqs_off, NULL);
> > +	register_trace_irq_enable(tracer_hardirqs_on, NULL);
> >  	return __irqsoff_tracer_init(tr);
> >  }
> >  
> >  static void irqsoff_tracer_reset(struct trace_array *tr)
> >  {
> > +	unregister_trace_irq_disable(tracer_hardirqs_off, NULL);
> > +	unregister_trace_irq_enable(tracer_hardirqs_on, NULL);
> >  	__irqsoff_tracer_reset(tr);
> >  }
> >  
> > @@ -692,19 +650,37 @@ static struct tracer irqsoff_tracer __read_mostly =
> >  };
> >  # define register_irqsoff(trace) register_tracer(&trace)
> >  #else
> > +static inline void tracer_hardirqs_on(unsigned long a0, unsigned long a1) { }
> > +static inline void tracer_hardirqs_off(unsigned long a0, unsigned long a1) { }
> 
> Just a nitpick.  These lines seem unnecessary since they're used
> only when CONFIG_IRQSOFF_TRACER is enabled AFAICS.
> 
> 
> >  # define register_irqsoff(trace) do { } while (0)
> > -#endif
> > +#endif /*  CONFIG_IRQSOFF_TRACER */
> >  
> >  #ifdef CONFIG_PREEMPT_TRACER
> > +static void tracer_preempt_on(void *none, unsigned long a0, unsigned long a1)
> > +{
> > +	if (preempt_trace() && !irq_trace())
> > +		stop_critical_timing(a0, a1);
> > +}
> > +
> > +static void tracer_preempt_off(void *none, unsigned long a0, unsigned long a1)
> > +{
> > +	if (preempt_trace() && !irq_trace())
> > +		start_critical_timing(a0, a1);
> > +}
> > +
> >  static int preemptoff_tracer_init(struct trace_array *tr)
> >  {
> >  	trace_type = TRACER_PREEMPT_OFF;
> >  
> > +	register_trace_preempt_disable(tracer_preempt_off, NULL);
> > +	register_trace_preempt_enable(tracer_preempt_on, NULL);
> >  	return __irqsoff_tracer_init(tr);
> >  }
> >  
> >  static void preemptoff_tracer_reset(struct trace_array *tr)
> >  {
> > +	unregister_trace_preempt_disable(tracer_preempt_off, NULL);
> > +	unregister_trace_preempt_enable(tracer_preempt_on, NULL);
> >  	__irqsoff_tracer_reset(tr);
> >  }
> >  
> > @@ -729,21 +705,32 @@ static struct tracer preemptoff_tracer __read_mostly =
> >  };
> >  # define register_preemptoff(trace) register_tracer(&trace)
> >  #else
> > +static inline void tracer_preempt_on(unsigned long a0, unsigned long a1) { }
> > +static inline void tracer_preempt_off(unsigned long a0, unsigned long a1) { }
> 
> Ditto (for CONFIG_PREEMPT_TRACER).
> 
> Thanks,
> Namhyung

Yes you're right, saves quite a few lines actually! I also inlined the
register_tracer macros, It seems much cleaner. I will fold the below diff but
let me know if there's anything else.

Thanks Namhyung!

 - Joel


---8<-----------------------

diff --git a/kernel/trace/trace_irqsoff.c b/kernel/trace/trace_irqsoff.c
index d2d8284088f0..d0bcb51d1a2a 100644
--- a/kernel/trace/trace_irqsoff.c
+++ b/kernel/trace/trace_irqsoff.c
@@ -648,11 +648,6 @@ static struct tracer irqsoff_tracer __read_mostly =
 	.allow_instances = true,
 	.use_max_tr	= true,
 };
-# define register_irqsoff(trace) register_tracer(&trace)
-#else
-static inline void tracer_hardirqs_on(unsigned long a0, unsigned long a1) { }
-static inline void tracer_hardirqs_off(unsigned long a0, unsigned long a1) { }
-# define register_irqsoff(trace) do { } while (0)
 #endif /*  CONFIG_IRQSOFF_TRACER */
 
 #ifdef CONFIG_PREEMPT_TRACER
@@ -703,11 +698,6 @@ static struct tracer preemptoff_tracer __read_mostly =
 	.allow_instances = true,
 	.use_max_tr	= true,
 };
-# define register_preemptoff(trace) register_tracer(&trace)
-#else
-static inline void tracer_preempt_on(unsigned long a0, unsigned long a1) { }
-static inline void tracer_preempt_off(unsigned long a0, unsigned long a1) { }
-# define register_preemptoff(trace) do { } while (0)
 #endif /* CONFIG_PREEMPT_TRACER */
 
 #if defined(CONFIG_IRQSOFF_TRACER) && defined(CONFIG_PREEMPT_TRACER)
@@ -753,18 +743,19 @@ static struct tracer preemptirqsoff_tracer __read_mostly =
 	.allow_instances = true,
 	.use_max_tr	= true,
 };
-
-# define register_preemptirqsoff(trace) register_tracer(&trace)
-#else
-# define register_preemptirqsoff(trace) do { } while (0)
 #endif
 
 __init static int init_irqsoff_tracer(void)
 {
-	register_irqsoff(irqsoff_tracer);
-	register_preemptoff(preemptoff_tracer);
-	register_preemptirqsoff(preemptirqsoff_tracer);
-
+#ifdef CONFIG_IRQSOFF_TRACER
+	register_tracer(&irqsoff_tracer);
+#endif
+#ifdef CONFIG_PREEMPT_TRACER
+	register_tracer(&preemptoff_tracer);
+#endif
+#if defined(CONFIG_IRQSOFF_TRACER) && defined(CONFIG_PREEMPT_TRACER)
+	register_tracer(&preemptirqsoff_tracer);
+#endif
 	return 0;
 }
 core_initcall(init_irqsoff_tracer);
--
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^ permalink raw reply	[flat|nested] 33+ messages in thread

* [PATCH v7 6/8] tracing: Centralize preemptirq tracepoints and unify their usage
@ 2018-05-25 23:20       ` joel
  0 siblings, 0 replies; 33+ messages in thread
From: Joel Fernandes @ 2018-05-25 23:20 UTC (permalink / raw)


On Fri, May 25, 2018@08:43:39PM +0900, Namhyung Kim wrote:
> Hi Joel,
> 
> On Wed, May 23, 2018@06:21:55PM -0700, Joel Fernandes wrote:
> > From: "Joel Fernandes (Google)" <joel at joelfernandes.org>
> > 
> > This patch detaches the preemptirq tracepoints from the tracers and
> > keeps it separate.
> > 
> > Advantages:
> > * Lockdep and irqsoff event can now run in parallel since they no longer
> > have their own calls.
> > 
> > * This unifies the usecase of adding hooks to an irqsoff and irqson
> > event, and a preemptoff and preempton event.
> >   3 users of the events exist:
> >   - Lockdep
> >   - irqsoff and preemptoff tracers
> >   - irqs and preempt trace events
> > 
> > The unification cleans up several ifdefs and makes the code in preempt
> > tracer and irqsoff tracers simpler. It gets rid of all the horrific
> > ifdeferry around PROVE_LOCKING and makes configuration of the different
> > users of the tracepoints more easy and understandable. It also gets rid
> > of the time_* function calls from the lockdep hooks used to call into
> > the preemptirq tracer which is not needed anymore. The negative delta in
> > lines of code in this patch is quite large too.
> > 
> [SNIP]
> >  
> >  #ifdef CONFIG_IRQSOFF_TRACER
> > +/*
> > + * We are only interested in hardirq on/off events:
> > + */
> > +static void tracer_hardirqs_on(void *none, unsigned long a0, unsigned long a1)
> > +{
> > +	if (!preempt_trace() && irq_trace())
> > +		stop_critical_timing(a0, a1);
> > +}
> > +
> > +static void tracer_hardirqs_off(void *none, unsigned long a0, unsigned long a1)
> > +{
> > +	if (!preempt_trace() && irq_trace())
> > +		start_critical_timing(a0, a1);
> > +}
> > +
> >  static int irqsoff_tracer_init(struct trace_array *tr)
> >  {
> >  	trace_type = TRACER_IRQS_OFF;
> >  
> > +	register_trace_irq_disable(tracer_hardirqs_off, NULL);
> > +	register_trace_irq_enable(tracer_hardirqs_on, NULL);
> >  	return __irqsoff_tracer_init(tr);
> >  }
> >  
> >  static void irqsoff_tracer_reset(struct trace_array *tr)
> >  {
> > +	unregister_trace_irq_disable(tracer_hardirqs_off, NULL);
> > +	unregister_trace_irq_enable(tracer_hardirqs_on, NULL);
> >  	__irqsoff_tracer_reset(tr);
> >  }
> >  
> > @@ -692,19 +650,37 @@ static struct tracer irqsoff_tracer __read_mostly =
> >  };
> >  # define register_irqsoff(trace) register_tracer(&trace)
> >  #else
> > +static inline void tracer_hardirqs_on(unsigned long a0, unsigned long a1) { }
> > +static inline void tracer_hardirqs_off(unsigned long a0, unsigned long a1) { }
> 
> Just a nitpick.  These lines seem unnecessary since they're used
> only when CONFIG_IRQSOFF_TRACER is enabled AFAICS.
> 
> 
> >  # define register_irqsoff(trace) do { } while (0)
> > -#endif
> > +#endif /*  CONFIG_IRQSOFF_TRACER */
> >  
> >  #ifdef CONFIG_PREEMPT_TRACER
> > +static void tracer_preempt_on(void *none, unsigned long a0, unsigned long a1)
> > +{
> > +	if (preempt_trace() && !irq_trace())
> > +		stop_critical_timing(a0, a1);
> > +}
> > +
> > +static void tracer_preempt_off(void *none, unsigned long a0, unsigned long a1)
> > +{
> > +	if (preempt_trace() && !irq_trace())
> > +		start_critical_timing(a0, a1);
> > +}
> > +
> >  static int preemptoff_tracer_init(struct trace_array *tr)
> >  {
> >  	trace_type = TRACER_PREEMPT_OFF;
> >  
> > +	register_trace_preempt_disable(tracer_preempt_off, NULL);
> > +	register_trace_preempt_enable(tracer_preempt_on, NULL);
> >  	return __irqsoff_tracer_init(tr);
> >  }
> >  
> >  static void preemptoff_tracer_reset(struct trace_array *tr)
> >  {
> > +	unregister_trace_preempt_disable(tracer_preempt_off, NULL);
> > +	unregister_trace_preempt_enable(tracer_preempt_on, NULL);
> >  	__irqsoff_tracer_reset(tr);
> >  }
> >  
> > @@ -729,21 +705,32 @@ static struct tracer preemptoff_tracer __read_mostly =
> >  };
> >  # define register_preemptoff(trace) register_tracer(&trace)
> >  #else
> > +static inline void tracer_preempt_on(unsigned long a0, unsigned long a1) { }
> > +static inline void tracer_preempt_off(unsigned long a0, unsigned long a1) { }
> 
> Ditto (for CONFIG_PREEMPT_TRACER).
> 
> Thanks,
> Namhyung

Yes you're right, saves quite a few lines actually! I also inlined the
register_tracer macros, It seems much cleaner. I will fold the below diff but
let me know if there's anything else.

Thanks Namhyung!

 - Joel


---8<-----------------------

diff --git a/kernel/trace/trace_irqsoff.c b/kernel/trace/trace_irqsoff.c
index d2d8284088f0..d0bcb51d1a2a 100644
--- a/kernel/trace/trace_irqsoff.c
+++ b/kernel/trace/trace_irqsoff.c
@@ -648,11 +648,6 @@ static struct tracer irqsoff_tracer __read_mostly =
 	.allow_instances = true,
 	.use_max_tr	= true,
 };
-# define register_irqsoff(trace) register_tracer(&trace)
-#else
-static inline void tracer_hardirqs_on(unsigned long a0, unsigned long a1) { }
-static inline void tracer_hardirqs_off(unsigned long a0, unsigned long a1) { }
-# define register_irqsoff(trace) do { } while (0)
 #endif /*  CONFIG_IRQSOFF_TRACER */
 
 #ifdef CONFIG_PREEMPT_TRACER
@@ -703,11 +698,6 @@ static struct tracer preemptoff_tracer __read_mostly =
 	.allow_instances = true,
 	.use_max_tr	= true,
 };
-# define register_preemptoff(trace) register_tracer(&trace)
-#else
-static inline void tracer_preempt_on(unsigned long a0, unsigned long a1) { }
-static inline void tracer_preempt_off(unsigned long a0, unsigned long a1) { }
-# define register_preemptoff(trace) do { } while (0)
 #endif /* CONFIG_PREEMPT_TRACER */
 
 #if defined(CONFIG_IRQSOFF_TRACER) && defined(CONFIG_PREEMPT_TRACER)
@@ -753,18 +743,19 @@ static struct tracer preemptirqsoff_tracer __read_mostly =
 	.allow_instances = true,
 	.use_max_tr	= true,
 };
-
-# define register_preemptirqsoff(trace) register_tracer(&trace)
-#else
-# define register_preemptirqsoff(trace) do { } while (0)
 #endif
 
 __init static int init_irqsoff_tracer(void)
 {
-	register_irqsoff(irqsoff_tracer);
-	register_preemptoff(preemptoff_tracer);
-	register_preemptirqsoff(preemptirqsoff_tracer);
-
+#ifdef CONFIG_IRQSOFF_TRACER
+	register_tracer(&irqsoff_tracer);
+#endif
+#ifdef CONFIG_PREEMPT_TRACER
+	register_tracer(&preemptoff_tracer);
+#endif
+#if defined(CONFIG_IRQSOFF_TRACER) && defined(CONFIG_PREEMPT_TRACER)
+	register_tracer(&preemptirqsoff_tracer);
+#endif
 	return 0;
 }
 core_initcall(init_irqsoff_tracer);
--
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^ permalink raw reply	[flat|nested] 33+ messages in thread

end of thread, other threads:[~2018-05-25 23:20 UTC | newest]

Thread overview: 33+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2018-05-24  1:21 [PATCH v7 0/8] Centralize and unify usage of preempt/irq tracepoints Joel Fernandes
2018-05-24  1:21 ` Joel Fernandes
2018-05-24  1:21 ` joelaf
2018-05-24  1:21 ` [PATCH v7 1/8] softirq: reorder trace_softirqs_on to prevent lockdep splat Joel Fernandes
2018-05-24  1:21   ` Joel Fernandes
2018-05-24  1:21   ` joelaf
2018-05-24  1:21 ` [PATCH v7 2/8] srcu: Add notrace variants of srcu_read_{lock,unlock} Joel Fernandes
2018-05-24  1:21   ` Joel Fernandes
2018-05-24  1:21   ` joelaf
2018-05-24  1:21 ` [PATCH v7 3/8] srcu: Add notrace variant of srcu_dereference Joel Fernandes
2018-05-24  1:21   ` Joel Fernandes
2018-05-24  1:21   ` joelaf
2018-05-24  1:21 ` [PATCH v7 4/8] trace/irqsoff: Split reset into separate functions Joel Fernandes
2018-05-24  1:21   ` Joel Fernandes
2018-05-24  1:21   ` joelaf
2018-05-24  1:21 ` [PATCH v7 5/8] tracepoint: Make rcuidle tracepoint callers use SRCU Joel Fernandes
2018-05-24  1:21   ` Joel Fernandes
2018-05-24  1:21   ` joelaf
2018-05-24  1:21 ` [PATCH v7 6/8] tracing: Centralize preemptirq tracepoints and unify their usage Joel Fernandes
2018-05-24  1:21   ` Joel Fernandes
2018-05-24  1:21   ` joelaf
2018-05-25 11:43   ` Namhyung Kim
2018-05-25 11:43     ` Namhyung Kim
2018-05-25 11:43     ` namhyung
2018-05-25 23:20     ` Joel Fernandes
2018-05-25 23:20       ` Joel Fernandes
2018-05-25 23:20       ` joel
2018-05-24  1:21 ` [PATCH v7 7/8] lib: Add module to simulate atomic sections for testing preemptoff tracers Joel Fernandes
2018-05-24  1:21   ` Joel Fernandes
2018-05-24  1:21   ` joelaf
2018-05-24  1:21 ` [PATCH v7 8/8] kselftests: Add tests for the preemptoff and irqsoff tracers Joel Fernandes
2018-05-24  1:21   ` Joel Fernandes
2018-05-24  1:21   ` joelaf

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