Commit b5230b56 authored by Li Zefan's avatar Li Zefan Committed by Ingo Molnar

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: default avatarLi Zefan <lizf@cn.fujitsu.com>
Acked-by: default avatarJens Axboe <jens.axboe@oracle.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent 6c051ce0
...@@ -426,11 +426,15 @@ int do_blk_trace_setup(struct request_queue *q, char *name, dev_t dev, ...@@ -426,11 +426,15 @@ int do_blk_trace_setup(struct request_queue *q, char *name, dev_t dev,
ret = -ENOENT; ret = -ENOENT;
mutex_lock(&blk_tree_mutex);
if (!blk_tree_root) { if (!blk_tree_root) {
blk_tree_root = debugfs_create_dir("block", NULL); blk_tree_root = debugfs_create_dir("block", NULL);
if (!blk_tree_root) if (!blk_tree_root) {
mutex_unlock(&blk_tree_mutex);
goto err; goto err;
} }
}
mutex_unlock(&blk_tree_mutex);
dir = debugfs_create_dir(buts->name, blk_tree_root); dir = debugfs_create_dir(buts->name, blk_tree_root);
......
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