[12/54] ring-buffer: Add interface for setting absolute time stamps

Commit Message

[e-mail] Aug. 29, 2018, 12:17 p.m. UTC

Define a new function, tracing_set_time_stamp_abs(), which can be used
to enable or disable the use of absolute timestamps rather than time
deltas for a trace array.

Only the interface is added here; a subsequent patch will add the
underlying implementation.

Link: http://lkml.kernel.org/r/ce9[e-mail]

Signed-off-by: Tom Zanussi <[e-mail]>
Signed-off-by: Baohong Liu <[e-mail]>
Signed-off-by: Steven Rostedt (VMware) <[e-mail]>
(cherry picked from commit 00b4145298aeb05a2d110117ed18148cb21ebd14)
Signed-off-by: Hirotaka MOTAI <[e-mail]>
---
 include/linux/ring_buffer.h |  2 ++
 kernel/trace/ring_buffer.c  | 11 +++++++++++
 kernel/trace/trace.c        | 33 ++++++++++++++++++++++++++++++++-
 kernel/trace/trace.h        |  3 +++
 4 files changed, 48 insertions(+), 1 deletion(-)

Patch

diff --git a/include/linux/ring_buffer.h b/include/linux/ring_buffer.h
index 5caa062a..adffb56b 100644
--- a/include/linux/ring_buffer.h
+++ b/include/linux/ring_buffer.h
@@ -174,16 +174,18 @@  unsigned long ring_buffer_commit_overrun_cpu(struct ring_buffer *buffer, int cpu
 unsigned long ring_buffer_dropped_events_cpu(struct ring_buffer *buffer, int cpu);
 unsigned long ring_buffer_read_events_cpu(struct ring_buffer *buffer, int cpu);
 
 u64 ring_buffer_time_stamp(struct ring_buffer *buffer, int cpu);
 void ring_buffer_normalize_time_stamp(struct ring_buffer *buffer,
 				      int cpu, u64 *ts);
 void ring_buffer_set_clock(struct ring_buffer *buffer,
 			   u64 (*clock)(void));
+void ring_buffer_set_time_stamp_abs(struct ring_buffer *buffer, bool abs);
+bool ring_buffer_time_stamp_abs(struct ring_buffer *buffer);
 
 size_t ring_buffer_page_len(void *page);
 
 
 void *ring_buffer_alloc_read_page(struct ring_buffer *buffer, int cpu);
 void ring_buffer_free_read_page(struct ring_buffer *buffer, int cpu, void *data);
 int ring_buffer_read_page(struct ring_buffer *buffer, void **data_page,
 			  size_t len, int cpu, int full);
diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index e3769d3c..eed0e343 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -483,16 +483,17 @@  struct ring_buffer {
 	struct mutex			mutex;
 
 	struct ring_buffer_per_cpu	**buffers;
 
 	struct hlist_node		node;
 	u64				(*clock)(void);
 
 	struct rb_irq_work		irq_work;
+	bool				time_stamp_abs;
 };
 
 struct ring_buffer_iter {
 	struct ring_buffer_per_cpu	*cpu_buffer;
 	unsigned long			head;
 	struct buffer_page		*head_page;
 	struct buffer_page		*cache_reader_page;
 	unsigned long			cache_read;
@@ -1382,16 +1383,26 @@  ring_buffer_free(struct ring_buffer *buffer)
 EXPORT_SYMBOL_GPL(ring_buffer_free);
 
 void ring_buffer_set_clock(struct ring_buffer *buffer,
 			   u64 (*clock)(void))
 {
 	buffer->clock = clock;
 }
 
+void ring_buffer_set_time_stamp_abs(struct ring_buffer *buffer, bool abs)
+{
+	buffer->time_stamp_abs = abs;
+}
+
+bool ring_buffer_time_stamp_abs(struct ring_buffer *buffer)
+{
+	return buffer->time_stamp_abs;
+}
+
 static void rb_reset_cpu(struct ring_buffer_per_cpu *cpu_buffer);
 
 static inline unsigned long rb_page_entries(struct buffer_page *bpage)
 {
 	return local_read(&bpage->entries) & RB_WRITE_MASK;
 }
 
 static inline unsigned long rb_page_write(struct buffer_page *bpage)
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 20919489..ef1489d4 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -2270,17 +2270,17 @@  trace_event_buffer_lock_reserve(struct ring_buffer **current_rb,
 			  int type, unsigned long len,
 			  unsigned long flags, int pc)
 {
 	struct ring_buffer_event *entry;
 	int val;
 
 	*current_rb = trace_file->tr->trace_buffer.buffer;
 
-	if ((trace_file->flags &
+	if (!ring_buffer_time_stamp_abs(*current_rb) && (trace_file->flags &
 	     (EVENT_FILE_FL_SOFT_DISABLED | EVENT_FILE_FL_FILTERED)) &&
 	    (entry = this_cpu_read(trace_buffered_event))) {
 		/* Try to use the per cpu buffer first */
 		val = this_cpu_inc_return(trace_buffered_event_cnt);
 		if (val == 1) {
 			trace_event_setup(entry, type, flags, pc);
 			entry->array[0] = len;
 			return entry;
@@ -6288,16 +6288,47 @@  static int tracing_clock_open(struct inode *inode, struct file *file)
 
 	ret = single_open(file, tracing_clock_show, inode->i_private);
 	if (ret < 0)
 		trace_array_put(tr);
 
 	return ret;
 }
 
+int tracing_set_time_stamp_abs(struct trace_array *tr, bool abs)
+{
+	int ret = 0;
+
+	mutex_lock(&trace_types_lock);
+
+	if (abs && tr->time_stamp_abs_ref++)
+		goto out;
+
+	if (!abs) {
+		if (WARN_ON_ONCE(!tr->time_stamp_abs_ref)) {
+			ret = -EINVAL;
+			goto out;
+		}
+
+		if (--tr->time_stamp_abs_ref)
+			goto out;
+	}
+
+	ring_buffer_set_time_stamp_abs(tr->trace_buffer.buffer, abs);
+
+#ifdef CONFIG_TRACER_MAX_TRACE
+	if (tr->max_buffer.buffer)
+		ring_buffer_set_time_stamp_abs(tr->max_buffer.buffer, abs);
+#endif
+ out:
+	mutex_unlock(&trace_types_lock);
+
+	return ret;
+}
+
 struct ftrace_buffer_info {
 	struct trace_iterator	iter;
 	void			*spare;
 	unsigned int		spare_cpu;
 	unsigned int		read;
 };
 
 #ifdef CONFIG_TRACER_SNAPSHOT
diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index 96c92f9c..5f1d4ae5 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -268,29 +268,32 @@  struct trace_array {
 	/* All of these are protected by the ftrace_lock */
 	struct list_head	func_probes;
 	struct list_head	mod_trace;
 	struct list_head	mod_notrace;
 #endif
 	/* function tracing enabled */
 	int			function_enabled;
 #endif
+	int			time_stamp_abs_ref;
 };
 
 enum {
 	TRACE_ARRAY_FL_GLOBAL	= (1 << 0)
 };
 
 extern struct list_head ftrace_trace_arrays;
 
 extern struct mutex trace_types_lock;
 
 extern int trace_array_get(struct trace_array *tr);
 extern void trace_array_put(struct trace_array *tr);
 
+extern int tracing_set_time_stamp_abs(struct trace_array *tr, bool abs);
+
 /*
  * The global tracer (top) should be the first trace array added,
  * but we check the flag anyway.
  */
 static inline struct trace_array *top_trace_array(void)
 {
 	struct trace_array *tr;