[tip:tracing/urgent] ftrace: Fix t_hash_start()

tip-bot for Li Zefan
2009-06-24T09:47:53Z

Commit-ID: d82d62444f87e5993af2fa82ed636b2206e052ea
Gitweb: http://git.kernel.org/tip/d82d62444f87e5993af2fa82ed636b2206e052ea
Author: Li Zefan <lizf@cn.fujitsu.com>
AuthorDate: Wed, 24 Jun 2009 09:54:54 +0800
Committer: Ingo Molnar <mingo@elte.hu>
CommitDate: Wed, 24 Jun 2009 11:02:53 +0200

ftrace: Fix t_hash_start()

When the output of set_ftrace_filter is larger than PAGE_SIZE,
t_hash_start() will be called the 2nd time, and then we start
from the head of a hlist, which is wrong and causes some entries
to be outputed twice.

The worse is, if the hlist is large enough, reading set_ftrace_filter
won't stop but in a dead loop.

Reviewed-by: Liming Wang <liming.wang@windriver.com>
Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
LKML-Reference: <4A41876E.2060407@cn.fujitsu.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

---
kernel/trace/ftrace.c | 12 +++++++++++-
1 files changed, 11 insertions(+), 1 deletions(-)

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index dc81020..71a52c1 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -1417,10 +1417,20 @@ static void *t_hash_start(struct seq_file *m, loff_t *pos)
{
struct ftrace_iterator *iter = m->private;
void *p = NULL;
+ loff_t l;
+
+ if (!(iter->flags & FTRACE_ITER_HASH))
+ *pos = 0;

iter->flags |= FTRACE_ITER_HASH;

- return t_hash_next(m, p, pos);
+ iter->hidx = 0;
+ for (l = 0; l <= *pos; ) {
+ p = t_hash_next(m, p, &l);
+ if (!p)
+ break;
+ }
+ return p;
}

static int t_hash_show(struct seq_file *m, void *v)