From: SeongJae Park <sjpark@xxxxxxxxx> 'reclaim_memory' callback can race with a driver code as this callback will be called from any memory pressure detected context. To deal with the case, this commit adds a spinlock in the 'xenbus_device'. Whenever 'reclaim_memory' callback is called, the lock of the device which passed to the callback as its argument is locked. Thus, drivers registering their 'reclaim_memory' callback should protect the data that might race with the callback with the lock by themselves. Signed-off-by: SeongJae Park <sjpark@xxxxxxxxx> --- drivers/xen/xenbus/xenbus_probe.c | 1 + drivers/xen/xenbus/xenbus_probe_backend.c | 10 ++++++++-- include/xen/xenbus.h | 2 ++ 3 files changed, 11 insertions(+), 2 deletions(-) diff --git a/drivers/xen/xenbus/xenbus_probe.c b/drivers/xen/xenbus/xenbus_probe.c index 5b471889d723..b86393f172e6 100644 --- a/drivers/xen/xenbus/xenbus_probe.c +++ b/drivers/xen/xenbus/xenbus_probe.c @@ -472,6 +472,7 @@ 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); diff --git a/drivers/xen/xenbus/xenbus_probe_backend.c b/drivers/xen/xenbus/xenbus_probe_backend.c index 7e78ebef7c54..516aa64b9967 100644 --- a/drivers/xen/xenbus/xenbus_probe_backend.c +++ b/drivers/xen/xenbus/xenbus_probe_backend.c @@ -251,12 +251,18 @@ 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; + unsigned long flags; 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); + spin_trylock_irqsave(&xdev->reclaim_lock, flags); + drv->reclaim_memory(xdev); + spin_unlock_irqrestore(&xdev->reclaim_lock, flags); + } return 0; } diff --git a/include/xen/xenbus.h b/include/xen/xenbus.h index c861cfb6f720..d9468313061d 100644 --- a/include/xen/xenbus.h +++ b/include/xen/xenbus.h @@ -76,6 +76,8 @@ struct xenbus_device { enum xenbus_state state; struct completion down; struct work_struct work; + /* 'reclaim_memory' callback is called while this lock is acquired */ + spinlock_t reclaim_lock; }; static inline struct xenbus_device *to_xenbus_device(struct device *dev) -- 2.17.1