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Subject[driver-core PATCH v9 1/9] driver core: Establish order of operations for device_add and device_del via bitflag
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Add an additional bit flag to the device struct named "dead".

This additional flag provides a guarantee that when a device_del is
executed on a given interface an async worker will not attempt to attach
the driver following the earlier device_del call. Previously this
guarantee was not present and could result in the device_del call
attempting to remove a driver from an interface only to have the async
worker attempt to probe the driver later when it finally completes the
asynchronous probe call.

One additional change added was that I pulled the check for dev->driver
out of the __device_attach_driver call and instead placed it in the
__device_attach_async_helper call. This was motivated by the fact that the
only other caller of this, __device_attach, had already taken the
device_lock() and checked for dev->driver. Instead of testing for this
twice in this path it makes more sense to just consolidate the dev->dead
and dev->driver checks together into one set of checks.

Reviewed-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Alexander Duyck <alexander.h.duyck@linux.intel.com>
---
drivers/base/core.c | 11 +++++++++++
drivers/base/dd.c | 22 +++++++++++-----------
include/linux/device.h | 5 +++++
3 files changed, 27 insertions(+), 11 deletions(-)

diff --git a/drivers/base/core.c b/drivers/base/core.c
index 0073b09bb99f..950e25495726 100644
--- a/drivers/base/core.c
+++ b/drivers/base/core.c
@@ -2080,6 +2080,17 @@ 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->dead = true;
+ device_unlock(dev);
+
/* Notify clients of device removal. This call must come
* before dpm_sysfs_remove().
*/
diff --git a/drivers/base/dd.c b/drivers/base/dd.c
index 88713f182086..74c194ac99df 100644
--- a/drivers/base/dd.c
+++ b/drivers/base/dd.c
@@ -731,15 +731,6 @@ static int __device_attach_driver(struct device_driver *drv, void *_data)
bool async_allowed;
int ret;

- /*
- * Check if device has already been claimed. This may
- * happen with driver loading, device discovery/registration,
- * and deferred probe processing happens all at once with
- * multiple threads.
- */
- if (dev->driver)
- return -EBUSY;
-
ret = driver_match_device(drv, dev);
if (ret == 0) {
/* no match */
@@ -774,6 +765,15 @@ static void __device_attach_async_helper(void *_dev, async_cookie_t cookie)

device_lock(dev);

+ /*
+ * Check if device has already been removed or claimed. This may
+ * happen with driver loading, device discovery/registration,
+ * and deferred probe processing happens all at once with
+ * multiple threads.
+ */
+ if (dev->dead || dev->driver)
+ goto out_unlock;
+
if (dev->parent)
pm_runtime_get_sync(dev->parent);

@@ -784,7 +784,7 @@ static void __device_attach_async_helper(void *_dev, async_cookie_t cookie)

if (dev->parent)
pm_runtime_put(dev->parent);
-
+out_unlock:
device_unlock(dev);

put_device(dev);
@@ -897,7 +897,7 @@ static int __driver_attach(struct device *dev, void *data)
if (dev->parent && dev->bus->need_parent_lock)
device_lock(dev->parent);
device_lock(dev);
- if (!dev->driver)
+ if (!dev->dead && !dev->driver)
driver_probe_device(drv, dev);
device_unlock(dev);
if (dev->parent && dev->bus->need_parent_lock)
diff --git a/include/linux/device.h b/include/linux/device.h
index 1b25c7a43f4c..f73dad81e811 100644
--- a/include/linux/device.h
+++ b/include/linux/device.h
@@ -957,6 +957,10 @@ struct dev_links_info {
* device.
* @dma_coherent: this particular device is dma coherent, even if the
* architecture supports non-coherent devices.
+ * @dead: This device is currently either in the process of or has
+ * been removed from the system. Any asynchronous events
+ * scheduled for this device should exit without taking any
+ * action.
*
* At the lowest level, every device in a Linux system is represented by an
* instance of struct device. The device structure contains the information
@@ -1051,6 +1055,7 @@ struct device {
defined(CONFIG_ARCH_HAS_SYNC_DMA_FOR_CPU_ALL)
bool dma_coherent:1;
#endif
+ bool dead:1;
};

static inline struct device *kobj_to_dev(struct kobject *kobj)
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