drivers/base: Introduce kill_device()

The libnvdimm subsystem arranges for devices to be destroyed as a result
of a sysfs operation. Since device_unregister() cannot be called from
an actively running sysfs attribute of the same device libnvdimm
arranges for device_unregister() to be performed in an out-of-line async
context.

The driver core maintains a 'dead' state for coordinating its own racing
async registration / de-registration requests. Rather than add local
'dead' state tracking infrastructure to libnvdimm device objects, export
the existing state tracking via a new kill_device() helper.

The kill_device() helper simply marks the device as dead, i.e. that it
is on its way to device_del(), or returns that the device was already
dead. This can be used in advance of calling device_unregister() for
subsystems like libnvdimm that might need to handle multiple user
threads racing to delete a device.

This refactoring does not change any behavior, but it is a pre-requisite
for follow-on fixes and therefore marked for -stable.

Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: "Rafael J. Wysocki" <rafael@kernel.org>
Fixes: 4d88a97aa9e8 ("libnvdimm, nvdimm: dimm driver and base libnvdimm device-driver...")
Cc: <stable@vger.kernel.org>
Tested-by: Jane Chu <jane.chu@oracle.com>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Link: https://lore.kernel.org/r/156341207332.292348.14959761496009347574.stgit@dwillia2-desk3.amr.corp.intel.com
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

diff --git a/drivers/base/core.c b/drivers/base/core.c
index fd7511e..eaf3aa0 100644 (file)
--- a/drivers/base/core.c
+++ b/drivers/base/core.c
@@ -2211,6 +2211,24 @@ void put_device(struct device *dev)
 }
 EXPORT_SYMBOL_GPL(put_device);
 
+bool kill_device(struct device *dev)
+{
+       /*
+        * Require the device lock and set the "dead" flag to guarantee that
+        * the update behavior is consistent with the other bitfields near
+        * it and that we cannot have an asynchronous probe routine trying
+        * to run while we are tearing out the bus/class/sysfs from
+        * underneath the device.
+        */
+       lockdep_assert_held(&dev->mutex);
+
+       if (dev->p->dead)
+               return false;
+       dev->p->dead = true;
+       return true;
+}
+EXPORT_SYMBOL_GPL(kill_device);
+
 /**
  * device_del - delete device from system.
  * @dev: device.
@@ -2230,15 +2248,8 @@ void device_del(struct device *dev)
        struct kobject *glue_dir = NULL;
        struct class_interface *class_intf;
 
-       /*
-        * Hold the device lock and set the "dead" flag to guarantee that
-        * the update behavior is consistent with the other bitfields near
-        * it and that we cannot have an asynchronous probe routine trying
-        * to run while we are tearing out the bus/class/sysfs from
-        * underneath the device.
-        */
        device_lock(dev);
-       dev->p->dead = true;
+       kill_device(dev);
        device_unlock(dev);
 
        /* Notify clients of device removal.  This call must come

diff --git a/include/linux/device.h b/include/linux/device.h
index e85264f..0da5c67 100644 (file)
--- a/include/linux/device.h
+++ b/include/linux/device.h
@@ -1373,6 +1373,7 @@ extern int (*platform_notify_remove)(struct device *dev);
  */
 extern struct device *get_device(struct device *dev);
 extern void put_device(struct device *dev);
+extern bool kill_device(struct device *dev);
 
 #ifdef CONFIG_DEVTMPFS
 extern int devtmpfs_create_node(struct device *dev);