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authorChris Mason <chris.mason@oracle.com>2009-09-16 03:57:42 +0400
committerChris Mason <chris.mason@oracle.com>2009-09-16 04:20:16 +0400
commit3e99d8eb347c93a5d38081380b8c9e69b203212e (patch)
tree1fde8df76b399c12827c2e2bd989e29e83d9994f
parent83ebade34bc1a90d0c3f77b87b940f336d075fda (diff)
downloadlinux-3e99d8eb347c93a5d38081380b8c9e69b203212e.tar.xz
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 <chris.mason@oracle.com>
-rw-r--r--fs/btrfs/async-thread.c14
1 files changed, 11 insertions, 3 deletions
diff --git a/fs/btrfs/async-thread.c b/fs/btrfs/async-thread.c
index 6ea5cd0a595f..73df627ab8ab 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);
}
}