Re: [tip:tracing/core] tracing/events: fix concurrent access to ftrace_events list

[Li Zefan <lizf@cn.fujitsu.com>]

tip-bot for Li Zefan wrote:
> Commit-ID:  20c8928abe70e204bd077ab6cfe23002d7788983
> Gitweb:     http://git.kernel.org/tip/20c8928abe70e204bd077ab6cfe23002d7788983
> Author:     Li Zefan <lizf@cn.fujitsu.com>
> AuthorDate: Wed, 6 May 2009 10:33:45 +0800
> Committer:  Ingo Molnar <mingo@elte.hu>
> CommitDate: Wed, 6 May 2009 10:38:19 +0200
> 
> tracing/events: fix concurrent access to ftrace_events list
> 

There is a deadlock in this patch, and I sent out a v2 patch and
expected it to be applied:
	http://lkml.org/lkml/2009/5/6/26

Below is a fix on top of this patch. Sorry for my carelessness.

=========

From: Li Zefan <lizf@cn.fujitsu.com>
Subject: [PATCH] tracing/events: fix deadlock on event_mutex

In filter_add_subsystem_pred() we should release event_mutex before
calling filter_free_subsystem_preds(), since both functions hold
event_mutex.

[ Impact: fix deadlock when writing invalid pred into subsystem filter ]

Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
---
 kernel/trace/trace_events_filter.c |    5 +++--
 1 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/kernel/trace/trace_events_filter.c b/kernel/trace/trace_events_filter.c
index 8c62e5b..85ad6a8 100644
--- a/kernel/trace/trace_events_filter.c
+++ b/kernel/trace/trace_events_filter.c
@@ -636,14 +636,15 @@ static int filter_add_subsystem_pred(struct filter_parse_state *ps,
 
 		err = filter_add_pred(ps, call, pred);
 		if (err) {
+			mutex_unlock(&event_mutex);
 			filter_free_subsystem_preds(system);
 			parse_error(ps, FILT_ERR_BAD_SUBSYS_FILTER, 0);
-			break;
+			goto out;
 		}
 		replace_filter_string(call->filter, filter_string);
 	}
 	mutex_unlock(&event_mutex);
-
+out:
 	return err;
 }
 
-- 
1.5.4.rc3