blktrace: fix a race when creating blk_tree_root in debugfs

t1                                t2
------                            ------
do_blk_trace_setup()              do_blk_trace_setup()
  if (!blk_tree_root) {
                                    if (!blk_tree_root)
    blk_tree_root = create_dir()
                                      blk_tree_root = create_dir();
                                      (now blk_tree_root == NULL)
  ...
  dir = create_dir(name, blk_tree_root);

Due to this race, t1 will create 'dir' in /debugfs but not /debugfs/block.

Signed-off-by: Li Zefan <[email protected]>
Acked-by: Jens Axboe <[email protected]>
Cc: Arnaldo Carvalho de Melo <[email protected]>
Cc: Steven Rostedt <[email protected]>
Cc: Frederic Weisbecker <[email protected]>
Signed-off-by: Ingo Molnar <[email protected]>

0 files changed, 0 insertions, 0 deletions