Messages in this thread Patch in this message | | | Date | Wed, 25 Mar 2009 17:19:33 +0800 | From | Li Zefan <> | Subject | [PATCH 2/3] blktrace: fix a race when creating blk_tree_root in debugfs |
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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> --- kernel/trace/blktrace.c | 6 +++++- 1 files changed, 5 insertions(+), 1 deletions(-)
diff --git a/kernel/trace/blktrace.c b/kernel/trace/blktrace.c index ee7a8bb..95f89fa 100644 --- a/kernel/trace/blktrace.c +++ b/kernel/trace/blktrace.c @@ -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); -- 1.5.4.rc3
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