| Message ID | 20191217160748.693-3-sjpark@amazon.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | xenbus/backend: Add a memory pressure handler callback | expand |
On 17.12.19 17:07, SeongJae Park wrote: > From: SeongJae Park <sjpark@amazon.de> > > '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@amazon.de> > --- > 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); You need spin_lock_irqsave() here. Or maybe spin_lock() would be fine, too? I can't see a reason why you'd want to disable irqs here. > + 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) > Juergen
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)