tracing: add lock depth to entries

This patch adds the lock depth of the big kernel lock to the generic
entry header. This way we can see the depth of the lock and help
in removing the BKL.

Example:

 #                  _------=> CPU#
 #                 / _-----=> irqs-off
 #                | / _----=> need-resched
 #                || / _---=> hardirq/softirq
 #                ||| / _--=> preempt-depth
 #                |||| /_--=> lock-depth
 #                |||||/     delay
 #  cmd     pid   |||||| time  |   caller
 #     \   /      ||||||   \   |   /
   <idle>-0       2.N..3 5902255250us+: lock_acquire: read rcu_read_lock
   <idle>-0       2.N..3 5902255253us+: lock_release: rcu_read_lock
   <idle>-0       2dN..3 5902255257us+: lock_acquire: xtime_lock
   <idle>-0       2dN..4 5902255259us : lock_acquire: clocksource_lock
   <idle>-0       2dN..4 5902255261us+: lock_release: clocksource_lock

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

1 files changed, 12 insertions, 4 deletions

diff --git a/kernel/trace/trace_functions_graph.c b/kernel/trace/trace_functions_graph.c
index ee791a9650c5..48af49374384 100644
--- a/kernel/trace/trace_functions_graph.c
+++ b/kernel/trace/trace_functions_graph.c
@@ -368,6 +368,7 @@ static enum print_line_t
 print_graph_lat_fmt(struct trace_seq *s, struct trace_entry *entry)
 {
         int hardirq, softirq;
+        int ret;
 
         hardirq = entry->flags & TRACE_FLAG_HARDIRQ;
         softirq = entry->flags & TRACE_FLAG_SOFTIRQ;
@@ -382,6 +383,13 @@ print_graph_lat_fmt(struct trace_seq *s, struct trace_entry *entry)
                                 hardirq ? 'h' : softirq ? 's' : '.'))
                 return 0;
 
+        if (entry->lock_depth < 0)
+                ret = trace_seq_putc(s, '.');
+        else
+                ret = trace_seq_printf(s, "%d", entry->lock_depth);
+        if (!ret)
+                return 0;
+
         if (entry->preempt_count)
                 return trace_seq_printf(s, "%x", entry->preempt_count);
         return trace_seq_puts(s, ".");
@@ -1001,8 +1009,8 @@ static void print_lat_header(struct seq_file *s)
         seq_printf(s, "#%.*s / _----=> need-resched    \n", size, spaces);
         seq_printf(s, "#%.*s| / _---=> hardirq/softirq \n", size, spaces);
         seq_printf(s, "#%.*s|| / _--=> preempt-depth   \n", size, spaces);
-        seq_printf(s, "#%.*s||| /                      \n", size, spaces);
-        seq_printf(s, "#%.*s||||                       \n", size, spaces);
+        seq_printf(s, "#%.*s||| / _-=> lock-depth      \n", size, spaces);
+        seq_printf(s, "#%.*s|||| /                     \n", size, spaces);
 }
 
 static void print_graph_headers(struct seq_file *s)
@@ -1021,7 +1029,7 @@ static void print_graph_headers(struct seq_file *s)
         if (tracer_flags.val & TRACE_GRAPH_PRINT_PROC)
                 seq_printf(s, "  TASK/PID       ");
         if (lat)
-                seq_printf(s, "||||");
+                seq_printf(s, "|||||");
         if (tracer_flags.val & TRACE_GRAPH_PRINT_DURATION)
                 seq_printf(s, "  DURATION   ");
         seq_printf(s, "               FUNCTION CALLS\n");
@@ -1035,7 +1043,7 @@ static void print_graph_headers(struct seq_file *s)
         if (tracer_flags.val & TRACE_GRAPH_PRINT_PROC)
                 seq_printf(s, "   |    |        ");
         if (lat)
-                seq_printf(s, "||||");
+                seq_printf(s, "|||||");
         if (tracer_flags.val & TRACE_GRAPH_PRINT_DURATION)
                 seq_printf(s, "   |   |      ");
         seq_printf(s, "               |   |   |   |\n");