linux-kernel - [PATCH 2/8] tracing: Add flag to control different traces

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Message-Id: <20201005071319.78508-3-alexander.shishkin@linux.intel.com>
Date:   Mon,  5 Oct 2020 10:13:13 +0300
From:   Alexander Shishkin <alexander.shishkin@...ux.intel.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     linux-kernel@...r.kernel.org,
        Tingwei Zhang <tingwei@...eaurora.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>
Subject: [PATCH 2/8] tracing: Add flag to control different traces

From: Tingwei Zhang <tingwei@...eaurora.org>

More traces like event trace or trace marker will be supported.
Add flag for difference traces, so that they can be controlled
separately. Move current function trace to it's own flag
instead of global ftrace enable flag.

Signed-off-by: Tingwei Zhang <tingwei@...eaurora.org>
Reviewed-by: Steven Rostedt (VMware) <rostedt@...dmis.org>
Reviewed-by: Alexander Shishkin <alexander.shishkin@...ux.intel.com>
Signed-off-by: Alexander Shishkin <alexander.shishkin@...ux.intel.com>
---
 include/linux/trace.h |  5 +++++
 kernel/trace/trace.c  | 36 +++++++++++++++++++-----------------
 2 files changed, 24 insertions(+), 17 deletions(-)

diff --git a/include/linux/trace.h b/include/linux/trace.h
index 36d255d66f88..c115a5d2269f 100644
--- a/include/linux/trace.h
+++ b/include/linux/trace.h
@@ -3,6 +3,9 @@
 #define _LINUX_TRACE_H
 
 #ifdef CONFIG_TRACING
+
+#define TRACE_EXPORT_FUNCTION	BIT(0)
+
 /*
  * The trace export - an export of Ftrace output. The trace_export
  * can process traces and export them to a registered destination as
@@ -15,10 +18,12 @@
  * next		- pointer to the next trace_export
  * write	- copy traces which have been delt with ->commit() to
  *		  the destination
+ * flags	- which ftrace to be exported
  */
 struct trace_export {
 	struct trace_export __rcu	*next;
 	void (*write)(struct trace_export *, const void *, unsigned int);
+	int flags;
 };
 
 int register_ftrace_export(struct trace_export *export);
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index f40d850ebabc..3ca121ad8728 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -2744,33 +2744,37 @@ trace_buffer_unlock_commit_nostack(struct trace_buffer *buffer,
 
 static void
 trace_process_export(struct trace_export *export,
-	       struct ring_buffer_event *event)
+	       struct ring_buffer_event *event, int flag)
 {
 	struct trace_entry *entry;
 	unsigned int size = 0;
 
-	entry = ring_buffer_event_data(event);
-	size = ring_buffer_event_length(event);
-	export->write(export, entry, size);
+	if (export->flags & flag) {
+		entry = ring_buffer_event_data(event);
+		size = ring_buffer_event_length(event);
+		export->write(export, entry, size);
+	}
 }
 
 static DEFINE_MUTEX(ftrace_export_lock);
 
 static struct trace_export __rcu *ftrace_exports_list __read_mostly;
 
-static DEFINE_STATIC_KEY_FALSE(ftrace_exports_enabled);
+static DEFINE_STATIC_KEY_FALSE(trace_function_exports_enabled);
 
-static inline void ftrace_exports_enable(void)
+static inline void ftrace_exports_enable(struct trace_export *export)
 {
-	static_branch_enable(&ftrace_exports_enabled);
+	if (export->flags & TRACE_EXPORT_FUNCTION)
+		static_branch_inc(&trace_function_exports_enabled);
 }
 
-static inline void ftrace_exports_disable(void)
+static inline void ftrace_exports_disable(struct trace_export *export)
 {
-	static_branch_disable(&ftrace_exports_enabled);
+	if (export->flags & TRACE_EXPORT_FUNCTION)
+		static_branch_dec(&trace_function_exports_enabled);
 }
 
-static void ftrace_exports(struct ring_buffer_event *event)
+static void ftrace_exports(struct ring_buffer_event *event, int flag)
 {
 	struct trace_export *export;
 
@@ -2778,7 +2782,7 @@ static void ftrace_exports(struct ring_buffer_event *event)
 
 	export = rcu_dereference_raw_check(ftrace_exports_list);
 	while (export) {
-		trace_process_export(export, event);
+		trace_process_export(export, event, flag);
 		export = rcu_dereference_raw_check(export->next);
 	}
 
@@ -2818,8 +2822,7 @@ rm_trace_export(struct trace_export **list, struct trace_export *export)
 static inline void
 add_ftrace_export(struct trace_export **list, struct trace_export *export)
 {
-	if (*list == NULL)
-		ftrace_exports_enable();
+	ftrace_exports_enable(export);
 
 	add_trace_export(list, export);
 }
@@ -2830,8 +2833,7 @@ rm_ftrace_export(struct trace_export **list, struct trace_export *export)
 	int ret;
 
 	ret = rm_trace_export(list, export);
-	if (*list == NULL)
-		ftrace_exports_disable();
+	ftrace_exports_disable(export);
 
 	return ret;
 }
@@ -2884,8 +2886,8 @@ trace_function(struct trace_array *tr,
 	entry->parent_ip		= parent_ip;
 
 	if (!call_filter_check_discard(call, entry, buffer, event)) {
-		if (static_branch_unlikely(&ftrace_exports_enabled))
-			ftrace_exports(event);
+		if (static_branch_unlikely(&trace_function_exports_enabled))
+			ftrace_exports(event, TRACE_EXPORT_FUNCTION);
 		__buffer_unlock_commit(buffer, event);
 	}
 }
-- 
2.28.0