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xenbus/backend: Protect xenbus callback with lock 

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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8
drivers/xen/xenbus/xenbus_probe.c
View File

@ -239,7 +239,9 @@ int xenbus_dev_probe(struct device *_dev)
goto fail;
}
spin_lock(&dev->reclaim_lock);
err = drv->probe(dev, id);
spin_unlock(&dev->reclaim_lock);
if (err)
goto fail_put;
@ -268,8 +270,11 @@ int xenbus_dev_remove(struct device *_dev)
free_otherend_watch(dev);
if (drv->remove)
if (drv->remove) {
spin_lock(&dev->reclaim_lock);
drv->remove(dev);
spin_unlock(&dev->reclaim_lock);
}
module_put(drv->driver.owner);
@ -468,6 +473,7 @@ int xenbus_probe_node(struct xen_bus_type *bus,
goto fail;
dev_set_name(&xendev->dev, "%s", devname);
spin_lock_init(&xendev->reclaim_lock);
/* Register with generic device framework. */
err = device_register(&xendev->dev);

10
drivers/xen/xenbus/xenbus_probe_backend.c
View File

@ -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;
}

1
include/xen/xenbus.h
View File

@ -76,6 +76,7 @@ struct xenbus_device {
enum xenbus_state state;
struct completion down;
struct work_struct work;
spinlock_t reclaim_lock;
};
static inline struct xenbus_device *to_xenbus_device(struct device *dev)