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net/9p/virtio: Fix hard lockup in req_done

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When client has multiple threads that issue io requests
all the time, and the server has a very good performance,
it may cause cpu is running in the irq context for a long
time because it can check virtqueue has buf in the *while*
loop.

So we should keep chan->lock in the whole loop.

[ Dominique: reworded subject line ]
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Yiwen Jiang <[email protected]>
To: Andrew Morton <[email protected]>
To: Eric Van Hensbergen <[email protected]>
To: Ron Minnich <[email protected]>
To: Latchesar Ionkov <[email protected]>
Signed-off-by: Dominique Martinet <[email protected]>
This commit is contained in:
jiangyiwen 2018-07-19 15:17:00 +08:00 • committed by Dominique Martinet
commit 31934da810
1 changed files with 11 additions and 10 deletions
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21
net/9p/trans_virtio.c
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@ -144,24 +144,25 @@ static void req_done(struct virtqueue *vq)
struct virtio_chan *chan = vq->vdev->priv;
unsigned int len;
struct p9_req_t *req;
bool need_wakeup = false;
unsigned long flags;
p9_debug(P9_DEBUG_TRANS, ": request done\n");
while (1) {
spin_lock_irqsave(&chan->lock, flags);
req = virtqueue_get_buf(chan->vq, &len);
if (req == NULL) {
spin_unlock_irqrestore(&chan->lock, flags);
break;
spin_lock_irqsave(&chan->lock, flags);
while ((req = virtqueue_get_buf(chan->vq, &len)) != NULL) {
if (!chan->ring_bufs_avail) {
chan->ring_bufs_avail = 1;
need_wakeup = true;
}
chan->ring_bufs_avail = 1;
spin_unlock_irqrestore(&chan->lock, flags);
/* Wakeup if anyone waiting for VirtIO ring space. */
wake_up(chan->vc_wq);
if (len)
p9_client_cb(chan->client, req, REQ_STATUS_RCVD);
}
spin_unlock_irqrestore(&chan->lock, flags);
/* Wakeup if anyone waiting for VirtIO ring space. */
if (need_wakeup)
wake_up(chan->vc_wq);
}
/**