Commit b5230b56 authored Mar 25, 2009 by Li Zefan Committed by Ingo Molnar Mar 31, 2009

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 <lizf@cn.fujitsu.com>
Acked-by: Jens 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: Ingo Molnar <mingo@elte.hu>

parent 6c051ce0

kernel/trace/blktrace.c

+5 −1

Original line number	Diff line number	Diff line
		@@ -426,11 +426,15 @@ int do_blk_trace_setup(struct request_queue q, char name, dev_t dev,

		ret = -ENOENT;

		mutex_lock(&blk_tree_mutex);
		if (!blk_tree_root) {
		blk_tree_root = debugfs_create_dir("block", NULL);
		if (!blk_tree_root)
		if (!blk_tree_root) {
		mutex_unlock(&blk_tree_mutex);
		goto err;
		}
		}
		mutex_unlock(&blk_tree_mutex);

		dir = debugfs_create_dir(buts->name, blk_tree_root);

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