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Subject[PATCH v7 2/2] tracing: Add support for preempt and irq enable/disable events
Date
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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