[RFC v2 3/4] tracing: Add support for display of tgid in trace output

[Joel Fernandes]

Earlier patches introduced ability to record the tgid using the 'record-tgid'
option. Here we read the tgid and output it if the option is enabled.

Cc: kernel-team@xxxxxxxxxxx
Cc: Steven Rostedt <rostedt@xxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx> 
Signed-off-by: Joel Fernandes <joelaf@xxxxxxxxxx>
---
 kernel/trace/trace.c        | 47 ++++++++++++++++++++++++++++++++-------------
 kernel/trace/trace_output.c |  9 +++++++++
 2 files changed, 43 insertions(+), 13 deletions(-)

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 7be21ae4f0a8..5883498754a1 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -3294,23 +3294,42 @@ static void print_event_info(struct trace_buffer *buf, struct seq_file *m)
 	seq_puts(m, "#\n");
 }
 
-static void print_func_help_header(struct trace_buffer *buf, struct seq_file *m)
+static void print_func_help_header(struct trace_buffer *buf, struct seq_file *m,
+				   unsigned int flags)
 {
 	print_event_info(buf, m);
-	seq_puts(m, "#           TASK-PID   CPU#      TIMESTAMP  FUNCTION\n"
-		    "#              | |       |          |         |\n");
+	if (!(flags & TRACE_ITER_RECORD_TGID)) {
+		seq_puts(m, "#           TASK-PID   CPU#      TIMESTAMP  FUNCTION\n"
+			    "#              | |       |          |         |\n");
+		return;
+	}
+
+	seq_puts(m, "#           TASK-PID   CPU#   TGID       TIMESTAMP  FUNCTION\n"
+		    "#              | |       |      |           |         |\n");
 }
 
-static void print_func_help_header_irq(struct trace_buffer *buf, struct seq_file *m)
+static void print_func_help_header_irq(struct trace_buffer *buf, struct seq_file *m,
+				       unsigned int flags)
 {
 	print_event_info(buf, m);
-	seq_puts(m, "#                              _-----=> irqs-off\n"
-		    "#                             / _----=> need-resched\n"
-		    "#                            | / _---=> hardirq/softirq\n"
-		    "#                            || / _--=> preempt-depth\n"
-		    "#                            ||| /     delay\n"
-		    "#           TASK-PID   CPU#  ||||    TIMESTAMP  FUNCTION\n"
-		    "#              | |       |   ||||       |         |\n");
+	if (!(flags & TRACE_ITER_RECORD_TGID)) {
+		seq_puts(m, "#                              _-----=> irqs-off\n"
+			    "#                             / _----=> need-resched\n"
+			    "#                            | / _---=> hardirq/softirq\n"
+			    "#                            || / _--=> preempt-depth\n"
+			    "#                            ||| /     delay\n"
+			    "#           TASK-PID   CPU#  ||||    TIMESTAMP  FUNCTION\n"
+			    "#              | |       |   ||||       |         |\n");
+		return;
+	}
+
+	seq_puts(m, "#                                      _-----=> irqs-off\n"
+		    "#                                     / _----=> need-resched\n"
+		    "#                                    | / _---=> hardirq/softirq\n"
+		    "#                                    || / _--=> preempt-depth\n"
+		    "#                                    ||| /     delay\n"
+		    "#           TASK-PID   CPU#   TGID   ||||    TIMESTAMP  FUNCTION\n"
+		    "#              | |       |      |    ||||       |         |\n");
 }
 
 void
@@ -3626,9 +3645,11 @@ void trace_default_header(struct seq_file *m)
 	} else {
 		if (!(trace_flags & TRACE_ITER_VERBOSE)) {
 			if (trace_flags & TRACE_ITER_IRQ_INFO)
-				print_func_help_header_irq(iter->trace_buffer, m);
+				print_func_help_header_irq(iter->trace_buffer,
+							   m, trace_flags);
 			else
-				print_func_help_header(iter->trace_buffer, m);
+				print_func_help_header(iter->trace_buffer, m,
+						       trace_flags);
 		}
 	}
 }
diff --git a/kernel/trace/trace_output.c b/kernel/trace/trace_output.c
index 08f9bab8089e..55c743295874 100644
--- a/kernel/trace/trace_output.c
+++ b/kernel/trace/trace_output.c
@@ -587,6 +587,15 @@ int trace_print_context(struct trace_iterator *iter)
 	trace_seq_printf(s, "%16s-%-5d [%03d] ",
 			       comm, entry->pid, iter->cpu);
 
+	if (tr->trace_flags & TRACE_ITER_RECORD_TGID) {
+		unsigned int tgid = trace_find_tgid(entry->pid);
+
+		if (!tgid)
+			trace_seq_printf(s, "(-----) ");
+		else
+			trace_seq_printf(s, "(%5d) ", tgid);
+	}
+
 	if (tr->trace_flags & TRACE_ITER_IRQ_INFO)
 		trace_print_lat_fmt(s, entry);
 
-- 
2.13.0.506.g27d5fe0cd-goog