[PATCH v4 2/3] 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>
Tested-by: Michael Sartain <mikesart@xxxxxxxxx>
Signed-off-by: Joel Fernandes <joelaf@xxxxxxxxxx>
---
 kernel/trace/trace.c        | 36 ++++++++++++++++++++++--------------
 kernel/trace/trace_output.c |  9 +++++++++
 2 files changed, 31 insertions(+), 14 deletions(-)

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 6dec7bef63c7..65878211f26f 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -3331,23 +3331,29 @@ 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)
 {
+	bool tgid = flags & TRACE_ITER_RECORD_TGID;
+
 	print_event_info(buf, m);
-	seq_puts(m, "#           TASK-PID   CPU#      TIMESTAMP  FUNCTION\n"
-		    "#              | |       |          |         |\n");
+
+	seq_printf(m, "#           TASK-PID   CPU#   %s  TIMESTAMP  FUNCTION\n", tgid ? "TGID     " : "");
+	seq_printf(m, "#              | |       |    %s     |         |\n",	 tgid ? "  |      " : "");
 }
 
-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");
+	bool tgid = flags & TRACE_ITER_RECORD_TGID;
+
+	seq_printf(m, "#                          %s  _-----=> irqs-off\n",	    tgid ? "          " : "");
+	seq_printf(m, "#                          %s / _----=> need-resched\n",	    tgid ? "          " : "");
+	seq_printf(m, "#                          %s| / _---=> hardirq/softirq\n",  tgid ? "          " : "");
+	seq_printf(m, "#                          %s|| / _--=> preempt-depth\n",    tgid ? "          " : "");
+	seq_printf(m, "#                          %s||| /     delay\n",		    tgid ? "          " : "");
+	seq_printf(m, "#           TASK-PID   CPU#%s||||    TIMESTAMP  FUNCTION\n", tgid ? "   TGID   " : "");
+	seq_printf(m, "#              | |       | %s||||       |         |\n",	    tgid ? "     |    " : "");
 }
 
 void
@@ -3663,9 +3669,11 @@ 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);
 
-- 
2.13.1.611.g7e3b11ae1-goog