[PATCH 23/25] xen: Lockdep fixes for xen-netfront

Jeremy Fitzhardinge
2007-04-23T23:13:36Z

[-- Attachment #1: xen-netfront-lockdep-fix.patch --]
[-- Type: text/plain, Size: 4227 bytes --]

netfront contains two locking problems found by lockdep:

1. rx_lock is a normal spinlock, and tx_lock is an irq spinlock. This
means that in normal use, tx_lock may be taken by an interrupt routine
while rx_lock is held. However, netif_disconnect_backend takes them
in the order tx_lock->rx_lock, which could lead to a deadlock. Reverse
them
2. rx_lock can also be taken in softirq context, so it should be taken/released
with spin_(un)lock_bh.

Signed-off-by: Jeremy Fitzhardinge <jeremy@xensource.com>
Cc: Chris Wright <chrisw@sous-sol.org>
Cc: Christian Limpach <Christian.Limpach@cl.cam.ac.uk>

---
drivers/net/xen-netfront.c | 30 +++++++++++++++---------------
1 file changed, 15 insertions(+), 15 deletions(-)

===================================================================
--- a/drivers/net/xen-netfront.c
+++ b/drivers/net/xen-netfront.c
@@ -515,14 +515,14 @@ static int network_open(struct net_devic

memset(&np->stats, 0, sizeof(np->stats));

- spin_lock(&np->rx_lock);
+ spin_lock_bh(&np->rx_lock);
if (netfront_carrier_ok(np)) {
network_alloc_rx_buffers(dev);
np->rx.sring->rsp_event = np->rx.rsp_cons + 1;
if (RING_HAS_UNCONSUMED_RESPONSES(&np->rx))
netif_rx_schedule(dev);
}
- spin_unlock(&np->rx_lock);
+ spin_unlock_bh(&np->rx_lock);

network_maybe_wake_tx(dev);

@@ -1212,10 +1212,10 @@ static int netif_poll(struct net_device
int pages_flipped = 0;
int err;

- spin_lock(&np->rx_lock);
+ spin_lock_bh(&np->rx_lock);

if (unlikely(!netfront_carrier_ok(np))) {
- spin_unlock(&np->rx_lock);
+ spin_unlock_bh(&np->rx_lock);
return 0;
}

@@ -1356,7 +1356,7 @@ err:
local_irq_restore(flags);
}

- spin_unlock(&np->rx_lock);
+ spin_unlock_bh(&np->rx_lock);

return more_to_do;
}
@@ -1399,7 +1399,7 @@ static void netif_release_rx_bufs(struct

skb_queue_head_init(&free_list);

- spin_lock(&np->rx_lock);
+ spin_lock_bh(&np->rx_lock);

for (id = 0; id < NET_RX_RING_SIZE; id++) {
if ((ref = np->grant_rx_ref[id]) == GRANT_INVALID_REF) {
@@ -1469,7 +1469,7 @@ static void netif_release_rx_bufs(struct
while ((skb = __skb_dequeue(&free_list)) != NULL)
dev_kfree_skb(skb);

- spin_unlock(&np->rx_lock);
+ spin_unlock_bh(&np->rx_lock);
}

static int network_close(struct net_device *dev)
@@ -1579,8 +1579,8 @@ static int network_connect(struct net_de
dev_info(&dev->dev, "has %sing receive path.\n",
np->copying_receiver ? "copy" : "flipp");

+ spin_lock_bh(&np->rx_lock);
spin_lock_irq(&np->tx_lock);
- spin_lock(&np->rx_lock);

/*
* Recovery procedure:
@@ -1632,8 +1632,8 @@ static int network_connect(struct net_de
network_tx_buf_gc(dev);
network_alloc_rx_buffers(dev);

- spin_unlock(&np->rx_lock);
spin_unlock_irq(&np->tx_lock);
+ spin_unlock_bh(&np->rx_lock);

return 0;
}
@@ -1689,7 +1689,7 @@ static ssize_t store_rxbuf_min(struct de
if (target > RX_MAX_TARGET)
target = RX_MAX_TARGET;

- spin_lock(&np->rx_lock);
+ spin_lock_bh(&np->rx_lock);
if (target > np->rx_max_target)
np->rx_max_target = target;
np->rx_min_target = target;
@@ -1698,7 +1698,7 @@ static ssize_t store_rxbuf_min(struct de

network_alloc_rx_buffers(netdev);

- spin_unlock(&np->rx_lock);
+ spin_unlock_bh(&np->rx_lock);
return len;
}

@@ -1732,7 +1732,7 @@ static ssize_t store_rxbuf_max(struct de
if (target > RX_MAX_TARGET)
target = RX_MAX_TARGET;

- spin_lock(&np->rx_lock);
+ spin_lock_bh(&np->rx_lock);
if (target < np->rx_min_target)
np->rx_min_target = target;
np->rx_max_target = target;
@@ -1741,7 +1741,7 @@ static ssize_t store_rxbuf_max(struct de

network_alloc_rx_buffers(netdev);

- spin_unlock(&np->rx_lock);
+ spin_unlock_bh(&np->rx_lock);
return len;
}

@@ -1885,11 +1885,11 @@ static void netif_disconnect_backend(str
static void netif_disconnect_backend(struct netfront_info *info)
{
/* Stop old i/f to prevent errors whilst we rebuild the state. */
+ spin_lock_bh(&info->rx_lock);
spin_lock_irq(&info->tx_lock);
- spin_lock(&info->rx_lock);
netfront_carrier_off(info);
- spin_unlock(&info->rx_lock);
spin_unlock_irq(&info->tx_lock);
+ spin_unlock_bh(&info->rx_lock);

if (info->irq)
unbind_from_irqhandler(info->irq, info->netdev);

--