tracing: Kill the unbalanced tr->ref++ in tracing_buffers_open()

commit e70e78e3c83b536730e31231dd9b979768d8df3c upstream.

tracing_buffers_open() does trace_array_get() and then it wrongly
inrcements tr->ref again under trace_types_lock. This means that
every caller leaks trace_array:

	# cd /sys/kernel/debug/tracing/
	# mkdir instances/X
	# true < instances/X/per_cpu/cpu0/trace_pipe_raw
	# rmdir instances/X
	rmdir: failed to remove `instances/X': Device or resource busy

Link: http://lkml.kernel.org/r/20130719153644.GA18899@redhat.com
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 97e750110b5aac93ae5e61bfc97703d1b6266f6f..073b9e041d32a32fdc000e19b2ccbea0d3dad661 100644 (file)
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -4907,8 +4907,6 @@ static int tracing_buffers_open(struct inode *inode, struct file *filp)
 
        mutex_lock(&trace_types_lock);
 
-       tr->ref++;
-
        info->iter.tr           = tr;
        info->iter.cpu_file     = tc->cpu;
        info->iter.trace        = tr->current_trace;