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| author | Chris Mason <chris.mason@oracle.com> | 2009-09-15 20:02:33 -0400 |
|---|---|---|
| committer | Chris Mason <chris.mason@oracle.com> | 2009-09-15 20:20:17 -0400 |
| commit | 6e74057c4686dc12ea767b4bdc50a63876056e1c (patch) | |
| tree | e7c70b8e08ab9e5363be28bcbcc72348122ae6e4 /fs/btrfs/async-thread.c | |
| parent | 627e421a3f35ad6b52dc58982fb6f8a97c30dcd7 (diff) | |
| download | lwn-6e74057c4686dc12ea767b4bdc50a63876056e1c.tar.gz lwn-6e74057c4686dc12ea767b4bdc50a63876056e1c.zip | |
Btrfs: Fix async thread shutdown race
It was possible for an async worker thread to be selected to
receive a new work item, but exit before the work item was
actually placed into that thread's work list.
This commit fixes the race by incrementing the num_pending
counter earlier, and making sure to check the number of pending
work items before a thread exits.
Signed-off-by: Chris Mason <chris.mason@oracle.com>
Diffstat (limited to 'fs/btrfs/async-thread.c')
| -rw-r--r-- | fs/btrfs/async-thread.c | 16 |
1 files changed, 10 insertions, 6 deletions
diff --git a/fs/btrfs/async-thread.c b/fs/btrfs/async-thread.c index 80e33bc96c84..282ca085c2fb 100644 --- a/fs/btrfs/async-thread.c +++ b/fs/btrfs/async-thread.c @@ -191,7 +191,8 @@ static int try_worker_shutdown(struct btrfs_worker_thread *worker) !worker->working && !list_empty(&worker->worker_list) && list_empty(&worker->prio_pending) && - list_empty(&worker->pending)) { + list_empty(&worker->pending) && + atomic_read(&worker->num_pending) == 0) { freeit = 1; list_del_init(&worker->worker_list); worker->workers->num_workers--; @@ -485,7 +486,6 @@ static struct btrfs_worker_thread *next_worker(struct btrfs_workers *workers) */ next = workers->worker_list.next; worker = list_entry(next, struct btrfs_worker_thread, worker_list); - atomic_inc(&worker->num_pending); worker->sequence++; if (worker->sequence % workers->idle_thresh == 0) @@ -521,8 +521,7 @@ again: goto again; } } - spin_unlock_irqrestore(&workers->lock, flags); - return worker; + goto found; fallback: fallback = NULL; @@ -537,6 +536,12 @@ fallback: BUG_ON(!fallback); worker = list_entry(fallback, struct btrfs_worker_thread, worker_list); +found: + /* + * this makes sure the worker doesn't exit before it is placed + * onto a busy/idle list + */ + atomic_inc(&worker->num_pending); spin_unlock_irqrestore(&workers->lock, flags); return worker; } @@ -569,7 +574,7 @@ int btrfs_requeue_work(struct btrfs_work *work) spin_lock(&worker->workers->lock); worker->idle = 0; list_move_tail(&worker->worker_list, - &worker->workers->worker_list); + &worker->workers->worker_list); spin_unlock(&worker->workers->lock); } if (!worker->working) { @@ -627,7 +632,6 @@ int btrfs_queue_worker(struct btrfs_workers *workers, struct btrfs_work *work) list_add_tail(&work->list, &worker->prio_pending); else list_add_tail(&work->list, &worker->pending); - atomic_inc(&worker->num_pending); check_busy_worker(worker); /* |