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xen-netback: fix a BUG() during initialization

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Commit edafc132baac ("xen-netback: making the bandwidth limiter runtime settable")
introduced the capability to change the bandwidth rate limit at runtime.
But it also introduced a possible crashing bug.

If netback receives two XenbusStateConnected without getting the
hotplug-status watch firing in between, then it will try to register the
watches for the rate limiter again.  But this triggers a BUG() in the watch
registration code.

The fix modifies connect() to remove the possibly existing packet-rate
watches before trying to install those watches.  This behaviour is in line
with how connect() deals with the hotplug-status watch.

Signed-off-by: Imre Palik <imrep@amazon.de>
Cc: Matt Wilson <msw@amazon.com>
Acked-by: Wei Liu <wei.liu2@citrix.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Palik, Imre 2015-06-19 14:21:51 +02:00 committed by David S. Miller
parent 754bc547f0
commit 12b322ac85
1 changed files with 4 additions and 0 deletions
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4
drivers/net/xen-netback/xenbus.c
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@ -681,6 +681,9 @@ static int xen_register_watchers(struct xenbus_device *dev, struct xenvif *vif)
char *node;
unsigned maxlen = strlen(dev->nodename) + sizeof("/rate");
if (vif->credit_watch.node)
return -EADDRINUSE;
node = kmalloc(maxlen, GFP_KERNEL);
if (!node)
return -ENOMEM;
@ -770,6 +773,7 @@ static void connect(struct backend_info *be)
}
xen_net_read_rate(dev, &credit_bytes, &credit_usec);
xen_unregister_watchers(be->vif);
xen_register_watchers(dev, be->vif);
read_xenbus_vif_flags(be);