Commit 95fdd5e9 authored Jul 06, 2012 by Neil Horman Committed by James Bottomley Jul 20, 2012

[SCSI] fcoe: Cleanup locking on fcoe_percpu_receive_thread

Noticed that we can shuffle the code around in fcoe_percpu_receive_thread a bit
and avoid taking the fcoe_rx_list lock twice per iteration. This should improve
throughput somewhat. With this change we take the lock, and check for new
frames in a single critical section. Only if the list is empty do we drop the
lock and re-acquire it after being signaled to wake up.

Change Notes:
v2) did some further cleanup on the patch by replacing the 2nd call of
spin_lock/splice_init with a goto to the top of the outer loop. This allows me
to change the inner while loop to an if conditional and remove the sencond check
of kthread_should_stop. Based on suggestion from Vasu Dev.

Signed-off-by: Neil Horman <nhorman@tuxdriver.com>
Acked-by: Vasu Dev <vasu.dev@intel.com>
Signed-off-by: Robert Love <robert.w.love@intel.com>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>

parent 902a45af

drivers/scsi/fcoe/fcoe.c

+10 −8

Original line number	Diff line number	Diff line
		@@ -1851,23 +1851,25 @@ static int fcoe_percpu_receive_thread(void *arg)

		set_user_nice(current, -20);

		retry:
		while (!kthread_should_stop()) {

		spin_lock_bh(&p->fcoe_rx_list.lock);
		skb_queue_splice_init(&p->fcoe_rx_list, &tmp);
		spin_unlock_bh(&p->fcoe_rx_list.lock);

		while ((skb = __skb_dequeue(&tmp)) != NULL)
		fcoe_recv_frame(skb);

		spin_lock_bh(&p->fcoe_rx_list.lock);
		if (!skb_queue_len(&p->fcoe_rx_list)) {
		if (!skb_queue_len(&tmp)) {
		set_current_state(TASK_INTERRUPTIBLE);
		spin_unlock_bh(&p->fcoe_rx_list.lock);
		schedule();
		set_current_state(TASK_RUNNING);
		} else
		goto retry;
		}

		spin_unlock_bh(&p->fcoe_rx_list.lock);

		while ((skb = __skb_dequeue(&tmp)) != NULL)
		fcoe_recv_frame(skb);

		}
		return 0;
		}

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