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drbd: add drbd_queue_work_if_unqueued helper 

We sometimes do
    if (list_empty(&w.list))
	drbd_queue_work(&q, &w.list);

Removal (list_del_init) may happen outside all locks, after all
pending work entries have been moved to an on-stack local work list.

For not dynamically allocated, but embeded, work structs,
we must avoid to re-add until it really was removed.

Move that list_empty check inside the spin_lock(&q->q_lock)
within the helper function, and change to list_empty_careful().

This may have been the reason for a list_add corruption
inside drbd_queue_work().

Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>
This commit is contained in:
Lars Ellenberg 2014-04-28 11:43:21 +02:00 committed by Philipp Reisner
parent 7f34f61490
commit 15e26f6a3c
2 changed files with 15 additions and 4 deletions
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11
drivers/block/drbd/drbd_int.h
View File

@ -1777,6 +1777,17 @@ drbd_queue_work(struct drbd_work_queue *q, struct drbd_work *w)
wake_up(&q->q_wait);
}
static inline void
drbd_queue_work_if_unqueued(struct drbd_work_queue *q, struct drbd_work *w)
{
unsigned long flags;
spin_lock_irqsave(&q->q_lock, flags);
if (list_empty_careful(&w->list))
list_add_tail(&w->list, &q->q);
spin_unlock_irqrestore(&q->q_lock, flags);
wake_up(&q->q_wait);
}
static inline void
drbd_device_post_work(struct drbd_device *device, int work_bit)
{

8
drivers/block/drbd/drbd_worker.c
View File

@ -452,9 +452,9 @@ void resync_timer_fn(unsigned long data)
{
struct drbd_device *device = (struct drbd_device *) data;
if (list_empty(&device->resync_work.list))
drbd_queue_work(&first_peer_device(device)->connection->sender_work,
&device->resync_work);
drbd_queue_work_if_unqueued(
&first_peer_device(device)->connection->sender_work,
&device->resync_work);
}
static void fifo_set(struct fifo_buffer *fb, int value)
@ -1968,7 +1968,7 @@ static void do_unqueued_work(struct drbd_connection *connection)
static bool dequeue_work_batch(struct drbd_work_queue *queue, struct list_head *work_list)
{
spin_lock_irq(&queue->q_lock);
list_splice_init(&queue->q, work_list);
list_splice_tail_init(&queue->q, work_list);
spin_unlock_irq(&queue->q_lock);
return !list_empty(work_list);
}