trace_stat: Fix missing entry in stat file

One entry is missing in the output of a stat file.

The cause is, when stat_seq_start() is called the 2nd time, we
should start from the (pos-1)th elem in the rbtree but not pos,
because pos == 0 is the header.

Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
LKML-Reference: <4A891A65.70009@cn.fujitsu.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 7 insertions, 3 deletions

diff --git a/kernel/trace/trace_stat.c b/kernel/trace/trace_stat.c
index 07c60b09258f..a4bb239eb987 100644
--- a/kernel/trace/trace_stat.c
+++ b/kernel/trace/trace_stat.c
@@ -203,17 +203,21 @@ static void *stat_seq_start(struct seq_file *s, loff_t *pos)
 {
         struct stat_session *session = s->private;
         struct rb_node *node;
+        int n = *pos;
         int i;
 
         /* Prevent from tracer switch or rbtree modification */
         mutex_lock(&session->stat_mutex);
 
         /* If we are in the beginning of the file, print the headers */
-        if (!*pos && session->ts->stat_headers)
-                return SEQ_START_TOKEN;
+        if (session->ts->stat_headers) {
+                if (n == 0)
+                        return SEQ_START_TOKEN;
+                n--;
+        }
 
         node = rb_first(&session->stat_root);
-        for (i = 0; node && i < *pos; i++)
+        for (i = 0; node && i < n; i++)
                 node = rb_next(node);
 
         return node;