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xenbus/backend: Protect xenbus callback with lock

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A driver's 'reclaim_memory' callback can race with 'probe' or 'remove'
because it will be called whenever memory pressure is detected.  To
avoid such race, this commit embeds a spinlock in each 'xenbus_device'
and make 'xenbus' to hold the lock while the corresponded callbacks are
running.

Reviewed-by: Juergen Gross <jgross@suse.com>
Signed-off-by: SeongJae Park <sjpark@amazon.de>
Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
This commit is contained in:
SeongJae Park
2020-01-27 09:18:09 +01:00
committed by Boris Ostrovsky
parent 8a105678fb
commit 060eabe8fb
3 changed files with 16 additions and 3 deletions
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10
drivers/xen/xenbus/xenbus_probe_backend.c
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@@ -250,12 +250,18 @@ static int backend_probe_and_watch(struct notifier_block *notifier,
static int backend_reclaim_memory(struct device *dev, void *data)
{
const struct xenbus_driver *drv;
struct xenbus_device *xdev;
if (!dev->driver)
return 0;
drv = to_xenbus_driver(dev->driver);
if (drv && drv->reclaim_memory)
drv->reclaim_memory(to_xenbus_device(dev));
if (drv && drv->reclaim_memory) {
xdev = to_xenbus_device(dev);
if (!spin_trylock(&xdev->reclaim_lock))
return 0;
drv->reclaim_memory(xdev);
spin_unlock(&xdev->reclaim_lock);
}
return 0;
}