Re: [driver-core PATCH v5 5/9] driver core: Establish clear order of operations for deferred probe and remove

This patch adds an additional bit to the device struct named async_probe. This additional bit 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(a)linux.intel.com&gt; --- drivers/base/dd.c | 104 +++++++++++++++++++++++++++--------------------- include/linux/device.h | 9 ++-- 2 files changed, 64 insertions(+), 49 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;