tracing: Synthetic event fixes and updates

If the ring_buffer reserve in synth_event_trace_start() fails, the matching ring_buffer_nest_end() should be called in the error code, since nothing else will ever call it in this case.

Signed-off-by Tom Zanussi <[email protected]>

---
 kernel/trace/trace_events_hist.c | 1 +
 1 file changed, 1 insertion(+)

kernel/trace/trace_events_hist.c +1 -0

index b3bcfd8c7332..a546ffa14785 100644
@@ -2043,6 +2043,7 @@ int synth_event_trace_start(struct trace_event_file *file,
 	entry = trace_event_buffer_reserve(&trace_state->fbuffer, file,
 					   sizeof(*entry) + fields_size);
 	if (!entry) {
+		ring_buffer_nest_end(trace_state->buffer);
 		ret = -EINVAL;
 		goto out;
 	}

Signature · 1 line

2.14.1

There's no reason to return -EINVAL when tracing a synthetic event if it's soft disabled - treat it the same as if it were hard disabled and return normally.

Have synth_event_trace() and synth_event_trace_array() just return normally, and have synth_event_trace_start set the trace state to disabled and return.

Signed-off-by Tom Zanussi <[email protected]>

---
 kernel/trace/trace_events_hist.c | 20 ++++++--------------
 1 file changed, 6 insertions(+), 14 deletions(-)

kernel/trace/trace_events_hist.c +6 -14

index a546ffa14785..99a02168599b 100644
@@ -1828,7 +1828,8 @@ int synth_event_trace(struct trace_event_file *file, unsigned int n_vals, ...)
 	 * called directly by the user, we don't have that but we
 	 * still need to honor not logging when disabled.
 	 */
-	if (!(file->flags & EVENT_FILE_FL_ENABLED))
+	if (!(file->flags & EVENT_FILE_FL_ENABLED) ||
+	    trace_trigger_soft_disabled(file))
 		return 0;
 
 	event = file->event_call->data;

@@ -1836,9 +1837,6 @@ int synth_event_trace(struct trace_event_file *file, unsigned int n_vals, ...)
 	if (n_vals != event->n_fields)
 		return -EINVAL;
 
-	if (trace_trigger_soft_disabled(file))
-		return -EINVAL;
-
 	fields_size = event->n_u64 * sizeof(u64);
 
 	/*

@@ -1918,7 +1916,8 @@ int synth_event_trace_array(struct trace_event_file *file, u64 *vals,
 	 * called directly by the user, we don't have that but we
 	 * still need to honor not logging when disabled.
 	 */
-	if (!(file->flags & EVENT_FILE_FL_ENABLED))
+	if (!(file->flags & EVENT_FILE_FL_ENABLED) ||
+	    trace_trigger_soft_disabled(file))
 		return 0;
 
 	event = file->event_call->data;

@@ -1926,9 +1925,6 @@ int synth_event_trace_array(struct trace_event_file *file, u64 *vals,
 	if (n_vals != event->n_fields)
 		return -EINVAL;
 
-	if (trace_trigger_soft_disabled(file))
-		return -EINVAL;
-
 	fields_size = event->n_u64 * sizeof(u64);
 
 	/*

@@ -2017,7 +2013,8 @@ int synth_event_trace_start(struct trace_event_file *file,
 	 * trace case, we save the enabed state upon start and just
 	 * ignore the following data calls.
 	 */
-	if (!(file->flags & EVENT_FILE_FL_ENABLED)) {
+	if (!(file->flags & EVENT_FILE_FL_ENABLED) ||
+	    trace_trigger_soft_disabled(file)) {
 		trace_state->enabled = false;
 		goto out;
 	}

@@ -2026,11 +2023,6 @@ int synth_event_trace_start(struct trace_event_file *file,
 
 	trace_state->event = file->event_call->data;
 
-	if (trace_trigger_soft_disabled(file)) {
-		ret = -EINVAL;
-		goto out;
-	}
-
 	fields_size = trace_state->event->n_u64 * sizeof(u64);
 
 	/*

Signature · 1 line

2.14.1

Quoted 4 lines · On Mon, 10 Feb 2020 17:06:49 -0600 Tom Zanussi <[email protected]> wrote:

There's no reason to return -EINVAL when tracing a synthetic event if it's soft disabled - treat it the same as if it were hard disabled and return normally.

Quoted 4 lines

Have synth_event_trace() and synth_event_trace_array() just return normally, and have synth_event_trace_start set the trace state to disabled and return.

Looks good to me.

Reviewed-by Masami Hiramatsu <[email protected]>

Move the checking, buffer reserve and buffer commit code in synth_event_trace_start/end() into inline functions __synth_event_trace_start/end() so they can also be used by synth_event_trace() and synth_event_trace_array(), and then have all those functions use them.

Also, change synth_event_trace_state.enabled to disabled so it only needs to be set if the event is disabled, which is not normally the case.

kernel/trace/trace_events_hist.c +10 -0

index 99a02168599b..65b54d6a1422 100644
@@ -1791,6 +1791,60 @@ void synth_event_cmd_init(struct dynevent_cmd *cmd, char *buf, int maxlen)
 }
 EXPORT_SYMBOL_GPL(synth_event_cmd_init);
 
+static inline int
+__synth_event_trace_start(struct trace_event_file *file,
+			  struct synth_event_trace_state *trace_state)
+{
+	int entry_size, fields_size = 0;
+	int ret = 0;
+
+	/*
+	 * Normal event tracing doesn't get called at all unless the
+	 * ENABLED bit is set (which attaches the probe thus allowing

kernel/trace/trace_events_hist.c +19 -0

+		goto out;
+	}
+
+	trace_state->event = file->event_call->data;
+
+	fields_size = trace_state->event->n_u64 * sizeof(u64);
+
+	/*
+	 * Avoid ring buffer recursion detection, as this event
+	 * is being performed within another event.
+	 */
+	trace_state->buffer = file->tr->array_buffer.buffer;
+	ring_buffer_nest_start(trace_state->buffer);
+
+	entry_size = sizeof(*trace_state->entry) + fields_size;
+	trace_state->entry = trace_event_buffer_reserve(&trace_state->fbuffer,
+							file,
+							entry_size);
+	if (!trace_state->entry) {

kernel/trace/trace_events_hist.c +6 -30

+	trace_event_buffer_commit(&trace_state->fbuffer);
+
+	ring_buffer_nest_end(trace_state->buffer);
+}
+
 /**
  * synth_event_trace - Trace a synthetic event
  * @file: The trace_event_file representing the synthetic event

@@ -1812,69 +1866,38 @@ EXPORT_SYMBOL_GPL(synth_event_cmd_init);
  */
 int synth_event_trace(struct trace_event_file *file, unsigned int n_vals, ...)
 {
-	struct trace_event_buffer fbuffer;
-	struct synth_trace_event *entry;
-	struct trace_buffer *buffer;
-	struct synth_event *event;
+	struct synth_event_trace_state state;
 	unsigned int i, n_u64;
-	int fields_size = 0;
 	va_list args;
-	int ret = 0;
-
-	/*
-	 * Normal event generation doesn't get called at all unless
-	 * the ENABLED bit is set (which attaches the probe thus
-	 * allowing this code to be called, etc).  Because this is
-	 * called directly by the user, we don't have that but we
-	 * still need to honor not logging when disabled.
-	 */
-	if (!(file->flags & EVENT_FILE_FL_ENABLED) ||
-	    trace_trigger_soft_disabled(file))
-		return 0;
-
-	event = file->event_call->data;
-
-	if (n_vals != event->n_fields)
-		return -EINVAL;
-
-	fields_size = event->n_u64 * sizeof(u64);
-
-	/*
-	 * Avoid ring buffer recursion detection, as this event
-	 * is being performed within another event.
-	 */
-	buffer = file->tr->array_buffer.buffer;

kernel/trace/trace_events_hist.c +8 -38

+		return ret;
 	}
 
 	va_start(args, n_vals);
-	for (i = 0, n_u64 = 0; i < event->n_fields; i++) {
+	for (i = 0, n_u64 = 0; i < state.event->n_fields; i++) {
 		u64 val;
 
 		val = va_arg(args, u64);
 
-		if (event->fields[i]->is_string) {
+		if (state.event->fields[i]->is_string) {
 			char *str_val = (char *)(long)val;
-			char *str_field = (char *)&entry->fields[n_u64];
+			char *str_field = (char *)&state.entry->fields[n_u64];
 
 			strscpy(str_field, str_val, STR_VAR_LEN_MAX);
 			n_u64 += STR_VAR_LEN_MAX / sizeof(u64);
 		} else {
-			entry->fields[n_u64] = val;
+			state.entry->fields[n_u64] = val;
 			n_u64++;
 		}
 	}
 	va_end(args);
 
-	trace_event_buffer_commit(&fbuffer);
-out:
-	ring_buffer_nest_end(buffer);
+	__synth_event_trace_end(&state);
 
 	return ret;
 }

@@ -1901,62 +1924,31 @@ EXPORT_SYMBOL_GPL(synth_event_trace);
 int synth_event_trace_array(struct trace_event_file *file, u64 *vals,
 			    unsigned int n_vals)
 {
-	struct trace_event_buffer fbuffer;
-	struct synth_trace_event *entry;
-	struct trace_buffer *buffer;
-	struct synth_event *event;
+	struct synth_event_trace_state state;
 	unsigned int i, n_u64;
-	int fields_size = 0;
-	int ret = 0;
-
-	/*
-	 * Normal event generation doesn't get called at all unless
-	 * the ENABLED bit is set (which attaches the probe thus
-	 * allowing this code to be called, etc).  Because this is
-	 * called directly by the user, we don't have that but we
-	 * still need to honor not logging when disabled.
-	 */
-	if (!(file->flags & EVENT_FILE_FL_ENABLED) ||
-	    trace_trigger_soft_disabled(file))
-		return 0;
-
-	event = file->event_call->data;
-
-	if (n_vals != event->n_fields)
-		return -EINVAL;
-
-	fields_size = event->n_u64 * sizeof(u64);
-
-	/*
-	 * Avoid ring buffer recursion detection, as this event
-	 * is being performed within another event.
-	 */
-	buffer = file->tr->array_buffer.buffer;
-	ring_buffer_nest_start(buffer);
+	int ret;

kernel/trace/trace_events_hist.c +9 -23

+		return ret;
 	}
 
-	for (i = 0, n_u64 = 0; i < event->n_fields; i++) {
-		if (event->fields[i]->is_string) {
+	for (i = 0, n_u64 = 0; i < state.event->n_fields; i++) {
+		if (state.event->fields[i]->is_string) {
 			char *str_val = (char *)(long)vals[i];
-			char *str_field = (char *)&entry->fields[n_u64];
+			char *str_field = (char *)&state.entry->fields[n_u64];
 
 			strscpy(str_field, str_val, STR_VAR_LEN_MAX);
 			n_u64 += STR_VAR_LEN_MAX / sizeof(u64);
 		} else {
-			entry->fields[n_u64] = vals[i];
+			state.entry->fields[n_u64] = vals[i];
 			n_u64++;
 		}
 	}
 
-	trace_event_buffer_commit(&fbuffer);
-out:
-	ring_buffer_nest_end(buffer);
+	__synth_event_trace_end(&state);
 
 	return ret;
 }

@@ -1993,55 +1985,17 @@ EXPORT_SYMBOL_GPL(synth_event_trace_array);
 int synth_event_trace_start(struct trace_event_file *file,
 			    struct synth_event_trace_state *trace_state)
 {
-	struct synth_trace_event *entry;
-	int fields_size = 0;
-	int ret = 0;
+	int ret;
 
-	if (!trace_state) {
-		ret = -EINVAL;
-		goto out;
-	}
+	if (!trace_state)
+		return -EINVAL;
 
 	memset(trace_state, '\0', sizeof(*trace_state));
 
-	/*
-	 * Normal event tracing doesn't get called at all unless the
-	 * ENABLED bit is set (which attaches the probe thus allowing
-	 * this code to be called, etc).  Because this is called
-	 * directly by the user, we don't have that but we still need
-	 * to honor not logging when disabled.  For the the iterated
-	 * trace case, we save the enabed state upon start and just
-	 * ignore the following data calls.
-	 */

kernel/trace/trace_events_hist.c +2 -25

-	trace_state->event = file->event_call->data;
-
-	fields_size = trace_state->event->n_u64 * sizeof(u64);
-
-	/*
-	 * Avoid ring buffer recursion detection, as this event
-	 * is being performed within another event.
-	 */
-	trace_state->buffer = file->tr->array_buffer.buffer;
-	ring_buffer_nest_start(trace_state->buffer);
-
-	entry = trace_event_buffer_reserve(&trace_state->fbuffer, file,
-					   sizeof(*entry) + fields_size);
-	if (!entry) {
-		ring_buffer_nest_end(trace_state->buffer);
-		ret = -EINVAL;
-		goto out;
-	}
-
-	trace_state->entry = entry;
-out:
 	return ret;
 }
 EXPORT_SYMBOL_GPL(synth_event_trace_start);

@@ -2074,7 +2028,7 @@ static int __synth_event_add_val(const char *field_name, u64 val,
 		trace_state->add_next = true;
 	}
 
-	if (!trace_state->enabled)
+	if (trace_state->disabled)
 		goto out;
 
 	event = trace_state->event;

@@ -2209,9 +2163,7 @@ int synth_event_trace_end(struct synth_event_trace_state *trace_state)
 	if (!trace_state)
 		return -EINVAL;
 
-	trace_event_buffer_commit(&trace_state->fbuffer);
-
-	ring_buffer_nest_end(trace_state->buffer);
+	__synth_event_trace_end(trace_state);
 
 	return 0;
 }

Signature · 1 line

2.14.1

Quoted 12 lines · On Wed, 12 Feb 2020 12:24:15 +0900 Masami Hiramatsu <[email protected]> wrote:

Quoted 8 lines · On Mon, 10 Feb 2020 17:06:49 -0600 Tom Zanussi <[email protected]> wrote:

There's no reason to return -EINVAL when tracing a synthetic event if it's soft disabled - treat it the same as if it were hard disabled and return normally.

Have synth_event_trace() and synth_event_trace_array() just return normally, and have synth_event_trace_start set the trace state to disabled and return.

Quoted 4 lines

Looks good to me.

Reviewed-by Masami Hiramatsu <[email protected]>

Thanks for the review Masami, but these patches have already landed in Linus's tree ;-)