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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>
This commit is contained in:
Chris Mason 2009-09-15 19:57:42 -04:00
parent 83ebade34b
commit 3e99d8eb34
1 changed files with 11 additions and 3 deletions
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14
fs/btrfs/async-thread.c
View File

@ -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);
}
}