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[PATCH v7 1/2] tracing: Prepare to add preempt and irq trace events

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  [PATCH v7 1/2] tracing: Prepare to add preempt and irq trace events Joel Fernandes <joelaf@google.com> - 2017-09-29 23:30 +0200
    [PATCH v7 2/2] tracing: Add support for preempt and irq enable/disable events Joel Fernandes <joelaf@google.com> - 2017-09-29 23:30 +0200

#1742366 — [PATCH v7 1/2] tracing: Prepare to add preempt and irq trace events

In preparation of adding irqsoff and preemptsoff enable and disable trace
events, move required functions and code to make it easier to add these events
in a later patch. This patch is just code movement and no functional change.

Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: kernel-team@android.com
Signed-off-by: Joel Fernandes <joelaf@google.com>
---
 kernel/trace/trace_irqsoff.c | 100 ++++++++++++++++++++++++++++++++-----------
 1 file changed, 74 insertions(+), 26 deletions(-)

diff --git a/kernel/trace/trace_irqsoff.c b/kernel/trace/trace_irqsoff.c
index 7758bc0617cb..0e3033c00474 100644
--- a/kernel/trace/trace_irqsoff.c
+++ b/kernel/trace/trace_irqsoff.c
@@ -16,6 +16,7 @@
 
 #include "trace.h"
 
+#if defined(CONFIG_IRQSOFF_TRACER) || defined(CONFIG_PREEMPT_TRACER)
 static struct trace_array		*irqsoff_trace __read_mostly;
 static int				tracer_enabled __read_mostly;
 
@@ -462,64 +463,44 @@ void time_hardirqs_off(unsigned long a0, unsigned long a1)
 
 #else /* !CONFIG_PROVE_LOCKING */
 
-/*
- * Stubs:
- */
-
-void trace_softirqs_on(unsigned long ip)
-{
-}
-
-void trace_softirqs_off(unsigned long ip)
-{
-}
-
-inline void print_irqtrace_events(struct task_struct *curr)
-{
-}
-
 /*
  * We are only interested in hardirq on/off events:
  */
-void trace_hardirqs_on(void)
+static inline void tracer_hardirqs_on(void)
 {
 	if (!preempt_trace() && irq_trace())
 		stop_critical_timing(CALLER_ADDR0, CALLER_ADDR1);
 }
-EXPORT_SYMBOL(trace_hardirqs_on);
 
-void trace_hardirqs_off(void)
+static inline void tracer_hardirqs_off(void)
 {
 	if (!preempt_trace() && irq_trace())
 		start_critical_timing(CALLER_ADDR0, CALLER_ADDR1);
 }
-EXPORT_SYMBOL(trace_hardirqs_off);
 
-__visible void trace_hardirqs_on_caller(unsigned long caller_addr)
+static inline void tracer_hardirqs_on_caller(unsigned long caller_addr)
 {
 	if (!preempt_trace() && irq_trace())
 		stop_critical_timing(CALLER_ADDR0, caller_addr);
 }
-EXPORT_SYMBOL(trace_hardirqs_on_caller);
 
-__visible void trace_hardirqs_off_caller(unsigned long 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);
 }
-EXPORT_SYMBOL(trace_hardirqs_off_caller);
 
 #endif /* CONFIG_PROVE_LOCKING */
 #endif /*  CONFIG_IRQSOFF_TRACER */
 
 #ifdef CONFIG_PREEMPT_TRACER
-void trace_preempt_on(unsigned long a0, unsigned long a1)
+static inline void tracer_preempt_on(unsigned long a0, unsigned long a1)
 {
 	if (preempt_trace() && !irq_trace())
 		stop_critical_timing(a0, a1);
 }
 
-void trace_preempt_off(unsigned long a0, unsigned long a1)
+static inline void tracer_preempt_off(unsigned long a0, unsigned long a1)
 {
 	if (preempt_trace() && !irq_trace())
 		start_critical_timing(a0, a1);
@@ -781,3 +762,70 @@ __init static int init_irqsoff_tracer(void)
 	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) { }
+#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)
+void trace_hardirqs_on(void)
+{
+	tracer_hardirqs_on();
+}
+EXPORT_SYMBOL(trace_hardirqs_on);
+
+void trace_hardirqs_off(void)
+{
+	tracer_hardirqs_off();
+}
+EXPORT_SYMBOL(trace_hardirqs_off);
+
+__visible void trace_hardirqs_on_caller(unsigned long caller_addr)
+{
+	tracer_hardirqs_on_caller(caller_addr);
+}
+EXPORT_SYMBOL(trace_hardirqs_on_caller);
+
+__visible void trace_hardirqs_off_caller(unsigned long 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
+
+#ifdef CONFIG_PREEMPT_TRACER
+void trace_preempt_on(unsigned long a0, unsigned long a1)
+{
+	tracer_preempt_on(a0, a1);
+}
+
+void trace_preempt_off(unsigned long a0, unsigned long a1)
+{
+	tracer_preempt_off(a0, a1);
+}
+#endif
-- 
2.14.2.822.g60be5d43e6-goog

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#1742369 — [PATCH v7 2/2] tracing: Add support for preempt and irq enable/disable events

Preempt and irq trace events can be used for tracing the start and
end of an atomic section which can be used by a trace viewer like
systrace to graphically view the start and end of an atomic section and
correlate them with latencies and scheduling issues.

This also serves as a prelude to using synthetic events or probes to
rewrite the preempt and irqsoff tracers, along with numerous benefits of
using trace events features for these events.

Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Peter Zilstra <peterz@infradead.org>
Cc: kernel-team@android.com
Signed-off-by: Joel Fernandes <joelaf@google.com>
---
 include/linux/ftrace.h            |  3 +-
 include/trace/events/preemptirq.h | 66 +++++++++++++++++++++++++++++++++++++++
 kernel/trace/Kconfig              |  9 ++++++
 kernel/trace/Makefile             |  1 +
 kernel/trace/trace_irqsoff.c      | 41 +++++++++++++++++++++++-
 5 files changed, 118 insertions(+), 2 deletions(-)
 create mode 100644 include/trace/events/preemptirq.h

diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
index 2e028854bac7..768e49b8c80f 100644
--- a/include/linux/ftrace.h
+++ b/include/linux/ftrace.h
@@ -742,7 +742,8 @@ static inline unsigned long get_lock_parent_ip(void)
   static inline void time_hardirqs_off(unsigned long a0, unsigned long a1) { }
 #endif
 
-#ifdef CONFIG_PREEMPT_TRACER
+#if defined(CONFIG_PREEMPT_TRACER) || \
+	(defined(CONFIG_DEBUG_PREEMPT) && defined(CONFIG_PREEMPTIRQ_EVENTS))
   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/trace/events/preemptirq.h b/include/trace/events/preemptirq.h
new file mode 100644
index 000000000000..734b7e2a3890
--- /dev/null
+++ b/include/trace/events/preemptirq.h
@@ -0,0 +1,66 @@
+#ifdef CONFIG_PREEMPTIRQ_EVENTS
+
+#undef TRACE_SYSTEM
+#define TRACE_SYSTEM preemptirq
+
+#if !defined(_TRACE_PREEMPTIRQ_H) || defined(TRACE_HEADER_MULTI_READ)
+#define _TRACE_PREEMPTIRQ_H
+
+#include <linux/ktime.h>
+#include <linux/tracepoint.h>
+#include <linux/string.h>
+#include <asm/sections.h>
+
+DECLARE_EVENT_CLASS(preemptirq_template,
+
+	TP_PROTO(unsigned long ip, unsigned long parent_ip),
+
+	TP_ARGS(ip, parent_ip),
+
+	TP_STRUCT__entry(
+		__field(u32, caller_offs)
+		__field(u32, parent_offs)
+	),
+
+	TP_fast_assign(
+		__entry->caller_offs = (u32)(ip - (unsigned long)_stext);
+		__entry->parent_offs = (u32)(parent_ip - (unsigned long)_stext);
+	),
+
+	TP_printk("caller=%pF parent=%pF",
+		  (void *)((unsigned long)(_stext) + __entry->caller_offs),
+		  (void *)((unsigned long)(_stext) + __entry->parent_offs))
+);
+
+DEFINE_EVENT(preemptirq_template, irq_disable,
+	     TP_PROTO(unsigned long ip, unsigned long parent_ip),
+	     TP_ARGS(ip, parent_ip));
+
+DEFINE_EVENT(preemptirq_template, irq_enable,
+	     TP_PROTO(unsigned long ip, unsigned long parent_ip),
+	     TP_ARGS(ip, parent_ip));
+
+DEFINE_EVENT(preemptirq_template, preempt_disable,
+	     TP_PROTO(unsigned long ip, unsigned long parent_ip),
+	     TP_ARGS(ip, parent_ip));
+
+DEFINE_EVENT(preemptirq_template, preempt_enable,
+	     TP_PROTO(unsigned long ip, unsigned long parent_ip),
+	     TP_ARGS(ip, parent_ip));
+
+#endif /* _TRACE_PREEMPTIRQ_H */
+
+#include <trace/define_trace.h>
+
+#else /* !CONFIG_PREEMPTIRQ_EVENTS */
+
+#define trace_irq_enable(...)
+#define trace_irq_disable(...)
+#define trace_preempt_enable(...)
+#define trace_preempt_disable(...)
+#define trace_irq_enable_rcuidle(...)
+#define trace_irq_disable_rcuidle(...)
+#define trace_preempt_enable_rcuidle(...)
+#define trace_preempt_disable_rcuidle(...)
+
+#endif
diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig
index 434c840e2d82..420666152de8 100644
--- a/kernel/trace/Kconfig
+++ b/kernel/trace/Kconfig
@@ -160,6 +160,15 @@ config FUNCTION_GRAPH_TRACER
 	  address on the current task structure into a stack of calls.
 
 
+config PREEMPTIRQ_EVENTS
+	bool "Enable trace events for preempt and irq disable/enable"
+	select TRACE_IRQFLAGS
+	default n
+	help
+	  Enable tracing of disable and enable events for preemption and irqs.
+	  For tracing preempt disable/enable events, CONFIG_DEBUG_PREEMPT must
+	  be enabled.
+
 config IRQSOFF_TRACER
 	bool "Interrupts-off Latency Tracer"
 	default n
diff --git a/kernel/trace/Makefile b/kernel/trace/Makefile
index 90f2701d92a7..9f62eee61f14 100644
--- a/kernel/trace/Makefile
+++ b/kernel/trace/Makefile
@@ -34,6 +34,7 @@ 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_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 0e3033c00474..515ac851841a 100644
--- a/kernel/trace/trace_irqsoff.c
+++ b/kernel/trace/trace_irqsoff.c
@@ -16,6 +16,9 @@
 
 #include "trace.h"
 
+#define CREATE_TRACE_POINTS
+#include <trace/events/preemptirq.h>
+
 #if defined(CONFIG_IRQSOFF_TRACER) || defined(CONFIG_PREEMPT_TRACER)
 static struct trace_array		*irqsoff_trace __read_mostly;
 static int				tracer_enabled __read_mostly;
@@ -776,27 +779,60 @@ 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
 
+/*
+ * trace_hardirqs_off can be called even when IRQs are already off. It is
+ * pointless and inconsistent with trace_preempt_enable and
+ * trace_preempt_disable to trace this, lets prevent double counting it with a
+ * per-cpu variable. Also reuse the per-cpu variable for other trace_hardirqs_*
+ * functions since we already define it.
+ */
+static DEFINE_PER_CPU(int, tracing_irq_cpu);
+
 #if defined(CONFIG_TRACE_IRQFLAGS) && !defined(CONFIG_PROVE_LOCKING)
 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);
@@ -818,14 +854,17 @@ inline void print_irqtrace_events(struct task_struct *curr)
 }
 #endif
 
-#ifdef CONFIG_PREEMPT_TRACER
+#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
-- 
2.14.2.822.g60be5d43e6-goog

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