From 3e99d8eb347c93a5d38081380b8c9e69b203212e Mon Sep 17 00:00:00 2001 From: Chris Mason Date: Tue, 15 Sep 2009 19:57:42 -0400 Subject: Btrfs: fix async worker startup race After a new worker thread starts, it is placed into the list of idle threads. But, this may race with a check for idle done by the worker thread itself, resulting in a double list_add operation. This fix adds a check to make sure the idle thread addition is done properly. Signed-off-by: Chris Mason --- fs/btrfs/async-thread.c | 14 +++++++++++--- 1 file changed, 11 insertions(+), 3 deletions(-) (limited to 'fs/btrfs/async-thread.c') diff --git a/fs/btrfs/async-thread.c b/fs/btrfs/async-thread.c index 6ea5cd0a595..73df627ab8a 100644 --- a/fs/btrfs/async-thread.c +++ b/fs/btrfs/async-thread.c @@ -74,7 +74,12 @@ static void check_idle_worker(struct btrfs_worker_thread *worker) unsigned long flags; spin_lock_irqsave(&worker->workers->lock, flags); worker->idle = 1; - list_move(&worker->worker_list, &worker->workers->idle_list); + + /* the list may be empty if the worker is just starting */ + if (!list_empty(&worker->worker_list)) { + list_move(&worker->worker_list, + &worker->workers->idle_list); + } spin_unlock_irqrestore(&worker->workers->lock, flags); } } @@ -90,8 +95,11 @@ static void check_busy_worker(struct btrfs_worker_thread *worker) unsigned long flags; spin_lock_irqsave(&worker->workers->lock, flags); worker->idle = 0; - list_move_tail(&worker->worker_list, - &worker->workers->worker_list); + + if (!list_empty(&worker->worker_list)) { + list_move_tail(&worker->worker_list, + &worker->workers->worker_list); + } spin_unlock_irqrestore(&worker->workers->lock, flags); } } -- cgit v1.2.3-18-g5258