From: Dan Williams dan.j.williams@intel.com
commit 00289cd87676e14913d2d8492d1ce05c4baafdae upstream.
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@dwi... Signed-off-by: Dan Williams dan.j.williams@intel.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- drivers/base/core.c | 27 +++++++++++++++++++-------- include/linux/device.h | 1 + 2 files changed, 20 insertions(+), 8 deletions(-)
--- 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 --- a/include/linux/device.h +++ b/include/linux/device.h @@ -1375,6 +1375,7 @@ extern int (*platform_notify_remove)(str */ 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);