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Subject[101/272] tracing: Fix preempt count leak
2.6.37-stable review patch.  If anyone has any objections, please let us know.

------------------

From: Li Zefan <lizf@cn.fujitsu.com>

commit 1dbd1951f39e13da579ffe879cce19586d0462de upstream.

While running my ftrace stress test, this showed up:

BUG: sleeping function called from invalid context at mm/mmap.c:233
...
note: cat[3293] exited with preempt_count 1

The bug was introduced by commit 91e86e560d0b3ce4c5fc64fd2bbb99f856a30a4e
("tracing: Fix recursive user stack trace")

Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
LKML-Reference: <4D0089AC.1020802@cn.fujitsu.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
kernel/trace/trace.c | 6 ++----
1 file changed, 2 insertions(+), 4 deletions(-)

--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -1313,12 +1313,10 @@ ftrace_trace_userstack(struct ring_buffe

__this_cpu_inc(user_stack_count);

-
-
event = trace_buffer_lock_reserve(buffer, TRACE_USER_STACK,
sizeof(*entry), flags, pc);
if (!event)
- return;
+ goto out_drop_count;
entry = ring_buffer_event_data(event);

entry->tgid = current->tgid;
@@ -1333,8 +1331,8 @@ ftrace_trace_userstack(struct ring_buffe
if (!filter_check_discard(call, entry, buffer, event))
ring_buffer_unlock_commit(buffer, event);

+ out_drop_count:
__this_cpu_dec(user_stack_count);
-
out:
preempt_enable();
}



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