[PATCH v2 1/1] devres: Enable trace events

[Andy Shevchenko]

In some cases the printf() mechanism is too heavy and can't be used.
For example, when debugging a race condition involving devres API.
When CONFIG_DEBUG_DEVRES is enabled I can't reproduce an issue, and
otherwise it's quite visible with a useful information being collected.

Enable trace events for devres part of the driver core.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>
---
v2: fixed compilation error (lkp), elaborate commit message (Greg)
 drivers/base/Makefile |  3 +++
 drivers/base/devres.c | 23 +++++++++++-------
 drivers/base/trace.c  | 10 ++++++++
 drivers/base/trace.h  | 56 +++++++++++++++++++++++++++++++++++++++++++
 4 files changed, 83 insertions(+), 9 deletions(-)
 create mode 100644 drivers/base/trace.c
 create mode 100644 drivers/base/trace.h

diff --git a/drivers/base/Makefile b/drivers/base/Makefile
index 8b93a7f291ec..ef8e44a7d288 100644
--- a/drivers/base/Makefile
+++ b/drivers/base/Makefile
@@ -30,3 +30,6 @@ obj-y			+= test/
 
 ccflags-$(CONFIG_DEBUG_DRIVER) := -DDEBUG
 
+# define_trace.h needs to know how to find our header
+CFLAGS_trace.o		:= -I$(src)
+obj-$(CONFIG_TRACING)	+= trace.o
diff --git a/drivers/base/devres.c b/drivers/base/devres.c
index db1f3137fc81..a0850bd1eab7 100644
--- a/drivers/base/devres.c
+++ b/drivers/base/devres.c
@@ -14,14 +14,13 @@
 #include <asm/sections.h>
 
 #include "base.h"
+#include "trace.h"
 
 struct devres_node {
 	struct list_head		entry;
 	dr_release_t			release;
-#ifdef CONFIG_DEBUG_DEVRES
 	const char			*name;
 	size_t				size;
-#endif
 };
 
 struct devres {
@@ -43,10 +42,6 @@ struct devres_group {
 	/* -- 8 pointers */
 };
 
-#ifdef CONFIG_DEBUG_DEVRES
-static int log_devres = 0;
-module_param_named(log, log_devres, int, S_IRUGO | S_IWUSR);
-
 static void set_node_dbginfo(struct devres_node *node, const char *name,
 			     size_t size)
 {
@@ -54,7 +49,11 @@ static void set_node_dbginfo(struct devres_node *node, const char *name,
 	node->size = size;
 }
 
-static void devres_log(struct device *dev, struct devres_node *node,
+#ifdef CONFIG_DEBUG_DEVRES
+static int log_devres = 0;
+module_param_named(log, log_devres, int, S_IRUGO | S_IWUSR);
+
+static void devres_dbg(struct device *dev, struct devres_node *node,
 		       const char *op)
 {
 	if (unlikely(log_devres))
@@ -62,10 +61,16 @@ static void devres_log(struct device *dev, struct devres_node *node,
 			op, node, node->name, node->size);
 }
 #else /* CONFIG_DEBUG_DEVRES */
-#define set_node_dbginfo(node, n, s)	do {} while (0)
-#define devres_log(dev, node, op)	do {} while (0)
+#define devres_dbg(dev, node, op)	do {} while (0)
 #endif /* CONFIG_DEBUG_DEVRES */
 
+static void devres_log(struct device *dev, struct devres_node *node,
+		       const char *op)
+{
+	trace_devres_log(dev, op, node, node->name, node->size);
+	devres_dbg(dev, node, op);
+}
+
 /*
  * Release functions for devres group.  These callbacks are used only
  * for identification.
diff --git a/drivers/base/trace.c b/drivers/base/trace.c
new file mode 100644
index 000000000000..b24b0a309c4a
--- /dev/null
+++ b/drivers/base/trace.c
@@ -0,0 +1,10 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Device core Trace Support
+ * Copyright (C) 2021, Intel Corporation
+ *
+ * Author: Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>
+ */
+
+#define CREATE_TRACE_POINTS
+#include "trace.h"
diff --git a/drivers/base/trace.h b/drivers/base/trace.h
new file mode 100644
index 000000000000..3192e18f877e
--- /dev/null
+++ b/drivers/base/trace.h
@@ -0,0 +1,56 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Device core Trace Support
+ * Copyright (C) 2021, Intel Corporation
+ *
+ * Author: Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>
+ */
+
+#undef TRACE_SYSTEM
+#define TRACE_SYSTEM dev
+
+#if !defined(__DEV_TRACE_H) || defined(TRACE_HEADER_MULTI_READ)
+#define __DEV_TRACE_H
+
+#include <linux/device.h>
+#include <linux/tracepoint.h>
+#include <linux/types.h>
+
+DECLARE_EVENT_CLASS(devres,
+	TP_PROTO(struct device *dev, const char *op, void *node, const char *name, size_t size),
+	TP_ARGS(dev, op, node, name, size),
+	TP_STRUCT__entry(
+		__string(devname, dev_name(dev))
+		__field(struct device *, dev)
+		__field(const char *, op)
+		__field(void *, node)
+		__field(const char *, name)
+		__field(size_t, size)
+	),
+	TP_fast_assign(
+		__assign_str(devname, dev_name(dev));
+		__entry->op = op;
+		__entry->node = node;
+		__entry->name = name;
+		__entry->size = size;
+	),
+	TP_printk("%s %3s %p %s (%zu bytes)", __get_str(devname),
+		  __entry->op, __entry->node, __entry->name, __entry->size)
+);
+
+DEFINE_EVENT(devres, devres_log,
+	TP_PROTO(struct device *dev, const char *op, void *node, const char *name, size_t size),
+	TP_ARGS(dev, op, node, name, size)
+);
+
+#endif /* __DEV_TRACE_H */
+
+/* this part has to be here */
+
+#undef TRACE_INCLUDE_PATH
+#define TRACE_INCLUDE_PATH .
+
+#undef TRACE_INCLUDE_FILE
+#define TRACE_INCLUDE_FILE trace
+
+#include <trace/define_trace.h>
-- 
2.30.2