tracing: Centralize preemptirq tracepoints and unify their usage

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

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.

This series + lockdep probes not registered (just to inject errors):
[    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  |

With this series + lockdep probes registered, all locking tests pass:

[    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  |

Link: http://lkml.kernel.org/r/20180730222423.196630-4-joel@joelfernandes.org

Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Namhyung Kim <namhyung@kernel.org>
Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

4 files changed, 147 insertions, 180 deletions

diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig
index 4d4eb15cc7fd..036cec1fcd24 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
@@ -155,18 +164,20 @@ 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"
@@ -203,6 +214,7 @@ 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 81902a79e049..98d53b39a8ee 100644
--- a/kernel/trace/Makefile
+++ b/kernel/trace/Makefile
@@ -41,7 +41,7 @@ obj-$(CONFIG_TRACING_MAP) += tracing_map.o
 obj-$(CONFIG_PREEMPTIRQ_DELAY_TEST) += preemptirq_delay_test.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..770cd30cda40 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);
 }
 
@@ -690,21 +648,34 @@ static struct tracer irqsoff_tracer __read_mostly =
 	.allow_instances = true,
 	.use_max_tr	= true,
 };
-# define register_irqsoff(trace) register_tracer(&trace)
-#else
-# 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);
 }
 
@@ -727,23 +698,29 @@ static struct tracer preemptoff_tracer __read_mostly =
 	.allow_instances = true,
 	.use_max_tr	= true,
 };
-# define register_preemptoff(trace) register_tracer(&trace)
-#else
-# 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);
 }
 
@@ -766,115 +743,21 @@ 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);
-
-	return 0;
-}
-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) { }
+#ifdef CONFIG_IRQSOFF_TRACER
+	register_tracer(&irqsoff_tracer);
 #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) { }
+#ifdef CONFIG_PREEMPT_TRACER
+	register_tracer(&preemptoff_tracer);
 #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)
-{
-}
+#if defined(CONFIG_IRQSOFF_TRACER) && defined(CONFIG_PREEMPT_TRACER)
+	register_tracer(&preemptirqsoff_tracer);
 #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);
+	return 0;
 }
-#endif
+core_initcall(init_irqsoff_tracer);
+#endif /* IRQSOFF_TRACER || PREEMPTOFF_TRACER */
diff --git a/kernel/trace/trace_preemptirq.c b/kernel/trace/trace_preemptirq.c
new file mode 100644
index 000000000000..e76b78bf258e
--- /dev/null
+++ b/kernel/trace/trace_preemptirq.c
@@ -0,0 +1,72 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * 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 (!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 (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 (!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 (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