[lttng-dev] [PATCH lttng-modules] Add preemptirq instrumentation

[Michael Jeanson]

The tracepoints were introduced in kernl 4.15 alongside the config
option PREEMPTIRQ_EVENTS.

This enables 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.

See upstream commit:

  commit d59158162e032917a428704160a2063a02405ec6
  Author: Joel Fernandes <joelaf at google.com>
  Date:   Tue Oct 10 15:51:37 2017 -0700

    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.
    Link: http://lkml.kernel.org/r/20171006005432.14244-3-joelaf@google.com
    Link: http://lkml.kernel.org/r/20171010225137.17370-1-joelaf@google.com

Signed-off-by: Michael Jeanson <mjeanson at efficios.com>
---
 instrumentation/events/lttng-module/preemptirq.h | 72 ++++++++++++++++++++++++
 probes/Kbuild                                    |  4 ++
 probes/lttng-probe-preemptirq.c                  | 49 ++++++++++++++++
 3 files changed, 125 insertions(+)
 create mode 100644 instrumentation/events/lttng-module/preemptirq.h
 create mode 100644 probes/lttng-probe-preemptirq.c

diff --git a/instrumentation/events/lttng-module/preemptirq.h b/instrumentation/events/lttng-module/preemptirq.h
new file mode 100644
index 0000000..55f7aaa
--- /dev/null
+++ b/instrumentation/events/lttng-module/preemptirq.h
@@ -0,0 +1,72 @@
+#ifdef CONFIG_PREEMPTIRQ_EVENTS
+
+#undef TRACE_SYSTEM
+#define TRACE_SYSTEM preemptirq
+
+#if !defined(LTTNG_TRACE_PREEMPTIRQ_H) || defined(TRACE_HEADER_MULTI_READ)
+#define LTTNG_TRACE_PREEMPTIRQ_H
+
+#include <linux/ktime.h>
+#include <linux/string.h>
+#include <asm/sections.h>
+#include <probes/lttng-tracepoint-event.h>
+
+
+LTTNG_TRACEPOINT_EVENT_CLASS(preemptirq_template,
+
+	TP_PROTO(unsigned long ip, unsigned long parent_ip),
+
+	TP_ARGS(ip, parent_ip),
+
+	TP_FIELDS(
+		ctf_integer(unsigned long, caller, ip)
+		ctf_integer(unsigned long, parent, parent_ip)
+	)
+)
+
+#ifndef CONFIG_PROVE_LOCKING
+LTTNG_TRACEPOINT_EVENT_INSTANCE_MAP(preemptirq_template, irq_disable,
+
+	preemptirq_irq_disable,
+
+	TP_PROTO(unsigned long ip, unsigned long parent_ip),
+
+	TP_ARGS(ip, parent_ip)
+)
+
+LTTNG_TRACEPOINT_EVENT_INSTANCE_MAP(preemptirq_template, irq_enable,
+
+	preemptirq_irq_enable,
+
+	TP_PROTO(unsigned long ip, unsigned long parent_ip),
+
+	TP_ARGS(ip, parent_ip)
+)
+#endif /* !CONFIG_PROVE_LOCKING */
+
+#ifdef CONFIG_DEBUG_PREEMPT
+LTTNG_TRACEPOINT_EVENT_INSTANCE_MAP(preemptirq_template, preempt_disable,
+
+	preemptirq_preempt_disable,
+
+	TP_PROTO(unsigned long ip, unsigned long parent_ip),
+
+	TP_ARGS(ip, parent_ip)
+)
+
+LTTNG_TRACEPOINT_EVENT_INSTANCE_MAP(preemptirq_template, preempt_enable,
+
+	preemptirq_preempt_enable,
+
+	TP_PROTO(unsigned long ip, unsigned long parent_ip),
+
+	TP_ARGS(ip, parent_ip)
+)
+#endif /* CONFIG_DEBUG_PREEMPT */
+
+#endif /* LTTNG_TRACE_PREEMPTIRQ_H */
+
+/* This part must be outside protection */
+#include <probes/define_trace.h>
+
+#endif /* CONFIG_PREEMPTIRQ_EVENTS */
diff --git a/probes/Kbuild b/probes/Kbuild
index 70a3d86..ff9c5f5 100644
--- a/probes/Kbuild
+++ b/probes/Kbuild
@@ -266,4 +266,8 @@ ifneq ($(CONFIG_DYNAMIC_FTRACE),)
   endif
 endif # CONFIG_DYNAMIC_FTRACE
 
+ifneq ($(CONFIG_PREEMPTIRQ_EVENTS),)
+  obj-$(CONFIG_LTTNG) += lttng-probe-preemptirq.o
+endif # CONFIG_PREEMPTIRQ_EVENTS
+
 # vim:syntax=make
diff --git a/probes/lttng-probe-preemptirq.c b/probes/lttng-probe-preemptirq.c
new file mode 100644
index 0000000..1270771
--- /dev/null
+++ b/probes/lttng-probe-preemptirq.c
@@ -0,0 +1,49 @@
+/*
+ * probes/lttng-probe-preemptirq.c
+ *
+ * LTTng preemptirq probes.
+ *
+ * Copyright (C) 2010-2012 Mathieu Desnoyers <mathieu.desnoyers at efficios.com>
+ *               2017 Michael Jeanson <mjeanson at efficios.com>
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; only
+ * version 2.1 of the License.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#include <linux/module.h>
+#include <linux/uaccess.h>
+#include <lttng-tracer.h>
+
+/*
+ * Create the tracepoint static inlines from the kernel to validate that our
+ * trace event macros match the kernel we run on.
+ */
+#include <trace/events/preemptirq.h>
+
+/*
+ * Create LTTng tracepoint probes.
+ */
+#define LTTNG_PACKAGE_BUILD
+#define CREATE_TRACE_POINTS
+#define TRACE_INCLUDE_PATH instrumentation/events/lttng-module
+
+#include <instrumentation/events/lttng-module/preemptirq.h>
+
+MODULE_LICENSE("GPL and additional rights");
+MODULE_AUTHOR("Michael Jeanson <mjeanson at efficios.com>");
+MODULE_DESCRIPTION("LTTng preemptirq probes");
+MODULE_VERSION(__stringify(LTTNG_MODULES_MAJOR_VERSION) "."
+	__stringify(LTTNG_MODULES_MINOR_VERSION) "."
+	__stringify(LTTNG_MODULES_PATCHLEVEL_VERSION)
+	LTTNG_MODULES_EXTRAVERSION);
-- 
2.7.4