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Subject[driver-core PATCH v6 5/9] driver core: Establish clear order of operations for deferred probe and remove
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Add an additional bit flag to the device struct named async_probe. This
additional flag allows us to guarantee ordering between probe and remove
operations.

This allows us to guarantee that if we execute a remove operation or a
driver load attempt on a given interface it will not attempt to update the
driver member asynchronously following the earlier operation. Previously
this guarantee was not present and could result in us attempting to remove
a driver from an interface only to have it show up later when it is
asynchronously loaded.

One change I made in addition is I replaced the use of "bool X:1" to define
the bitfield to a "u8 X:1" setup in order to resolve some checkpatch
warnings.

Signed-off-by: Alexander Duyck <alexander.h.duyck@linux.intel.com>
---
drivers/base/dd.c | 104 +++++++++++++++++++++++++++---------------------
include/linux/device.h | 3 +
2 files changed, 62 insertions(+), 45 deletions(-)

diff --git a/drivers/base/dd.c b/drivers/base/dd.c
index e74cefeb5b69..ed19cf0d6f9a 100644
--- a/drivers/base/dd.c
+++ b/drivers/base/dd.c
@@ -472,6 +472,8 @@ static int really_probe(struct device *dev, struct device_driver *drv)
drv->bus->name, __func__, drv->name, dev_name(dev));
WARN_ON(!list_empty(&dev->devres_head));

+ /* clear async_probe flag as we are no longer deferring driver load */
+ dev->async_probe = false;
re_probe:
dev->driver = drv;

@@ -771,6 +773,10 @@ static void __device_attach_async_helper(void *_dev, async_cookie_t cookie)

device_lock(dev);

+ /* nothing to do if async_probe has been cleared */
+ if (!dev->async_probe)
+ goto out_unlock;
+
if (dev->parent)
pm_runtime_get_sync(dev->parent);

@@ -781,7 +787,7 @@ 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);
@@ -826,6 +832,7 @@ static int __device_attach(struct device *dev, bool allow_async)
*/
dev_dbg(dev, "scheduling asynchronous probe\n");
get_device(dev);
+ dev->async_probe = true;
async_schedule(__device_attach_async_helper, dev);
} else {
pm_request_idle(dev);
@@ -971,62 +978,69 @@ EXPORT_SYMBOL_GPL(driver_attach);
*/
static void __device_release_driver(struct device *dev, struct device *parent)
{
- struct device_driver *drv;
+ struct device_driver *drv = dev->driver;

- drv = dev->driver;
- if (drv) {
- while (device_links_busy(dev)) {
- __device_driver_unlock(dev, parent);
+ /*
+ * In the event that we are asked to release the driver on an
+ * interface that is still waiting on a probe we can just terminate
+ * the probe by setting async_probe to false. When the async call
+ * is finally completed it will see this state and just exit.
+ */
+ dev->async_probe = false;
+ if (!drv)
+ return;

- device_links_unbind_consumers(dev);
+ while (device_links_busy(dev)) {
+ __device_driver_unlock(dev, parent);

- __device_driver_lock(dev, parent);
- /*
- * A concurrent invocation of the same function might
- * have released the driver successfully while this one
- * was waiting, so check for that.
- */
- if (dev->driver != drv)
- return;
- }
+ device_links_unbind_consumers(dev);

- pm_runtime_get_sync(dev);
- pm_runtime_clean_up_links(dev);
+ __device_driver_lock(dev, parent);
+ /*
+ * A concurrent invocation of the same function might
+ * have released the driver successfully while this one
+ * was waiting, so check for that.
+ */
+ if (dev->driver != drv)
+ return;
+ }

- driver_sysfs_remove(dev);
+ pm_runtime_get_sync(dev);
+ pm_runtime_clean_up_links(dev);

- if (dev->bus)
- blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
- BUS_NOTIFY_UNBIND_DRIVER,
- dev);
+ driver_sysfs_remove(dev);

- pm_runtime_put_sync(dev);
+ if (dev->bus)
+ blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
+ BUS_NOTIFY_UNBIND_DRIVER,
+ dev);

- if (dev->bus && dev->bus->remove)
- dev->bus->remove(dev);
- else if (drv->remove)
- drv->remove(dev);
+ pm_runtime_put_sync(dev);

- device_links_driver_cleanup(dev);
- arch_teardown_dma_ops(dev);
+ if (dev->bus && dev->bus->remove)
+ dev->bus->remove(dev);
+ else if (drv->remove)
+ drv->remove(dev);

- devres_release_all(dev);
- dev->driver = NULL;
- dev_set_drvdata(dev, NULL);
- if (dev->pm_domain && dev->pm_domain->dismiss)
- dev->pm_domain->dismiss(dev);
- pm_runtime_reinit(dev);
- dev_pm_set_driver_flags(dev, 0);
+ device_links_driver_cleanup(dev);
+ arch_teardown_dma_ops(dev);
+
+ devres_release_all(dev);
+ dev->driver = NULL;
+ dev_set_drvdata(dev, NULL);
+ if (dev->pm_domain && dev->pm_domain->dismiss)
+ dev->pm_domain->dismiss(dev);
+ pm_runtime_reinit(dev);
+ dev_pm_set_driver_flags(dev, 0);

- klist_remove(&dev->p->knode_driver);
- device_pm_check_callbacks(dev);
- if (dev->bus)
- blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
- BUS_NOTIFY_UNBOUND_DRIVER,
- dev);
+ klist_remove(&dev->p->knode_driver);
+ device_pm_check_callbacks(dev);
+ if (dev->bus)
+ blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
+ BUS_NOTIFY_UNBOUND_DRIVER,
+ dev);

- kobject_uevent(&dev->kobj, KOBJ_UNBIND);
- }
+ kobject_uevent(&dev->kobj, KOBJ_UNBIND);
}

void device_release_driver_internal(struct device *dev,
diff --git a/include/linux/device.h b/include/linux/device.h
index 1b25c7a43f4c..4d2eb2c74149 100644
--- a/include/linux/device.h
+++ b/include/linux/device.h
@@ -957,6 +957,8 @@ struct dev_links_info {
* device.
* @dma_coherent: this particular device is dma coherent, even if the
* architecture supports non-coherent devices.
+ * @async_probe: This device has an asynchronous probe event pending. Should
+ * only be updated while holding device lock.
*
* 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 +1053,7 @@ struct device {
defined(CONFIG_ARCH_HAS_SYNC_DMA_FOR_CPU_ALL)
bool dma_coherent:1;
#endif
+ bool async_probe:1;
};

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