FROMLIST: 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.

Change-Id: I718d40f7c3c48579adf9d7121b21495a669c89bd
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Peter Zilstra <peterz@infradead.org>
Cc: kernel-team@android.com
Link: https://patchwork.kernel.org/patch/9988157/
Signed-off-by: Joel Fernandes <joelaf@google.com>

3 files changed, 46 insertions, 1 deletions

diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig
index 5f5b66a2f156..006eefb6ede0 100644
--- a/kernel/trace/Kconfig
+++ b/kernel/trace/Kconfig
@@ -165,6 +165,17 @@ 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
+	depends on DEBUG_PREEMPT || !PROVE_LOCKING
+	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"
 	default n
diff --git a/kernel/trace/Makefile b/kernel/trace/Makefile
index a9bba37fab5a..4b35fb97ae44 100644
--- a/kernel/trace/Makefile
+++ b/kernel/trace/Makefile
@@ -37,6 +37,7 @@ obj-$(CONFIG_TRACING) += trace_stat.o
 obj-$(CONFIG_TRACING) += trace_printk.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 0e56eace0dde..21b162c07e83 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;
@@ -765,27 +768,54 @@ 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
 
+/* Per-cpu variable to prevent redundant calls when IRQs already off */
+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);
@@ -807,14 +837,17 @@ 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