Re: [driver-core PATCH v8 2/9] driver core: Establish order of operations for device_add and device_del via bitflag

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.

Signed-off-by: Alexander Duyck <redacted>
---
 drivers/base/core.c    |   11 +++++++++++
 drivers/base/dd.c      |    8 ++++++--
 include/linux/device.h |    5 +++++
 3 files changed, 22 insertions(+), 2 deletions(-)

diff --git a/drivers/base/core.c b/drivers/base/core.c
index f3e6ca4170b4..70358327303b 100644
--- a/drivers/base/core.c
+++ b/drivers/base/core.c

@@ -2075,6 +2075,17 @@ 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..3bb8c3e0f3da 100644
--- a/drivers/base/dd.c
+++ b/drivers/base/dd.c

@@ -774,6 +774,10 @@ static void __device_attach_async_helper(void *_dev, async_cookie_t cookie)

        device_lock(dev);

+       /* device is or has been removed from the bus, just bail out */
+       if (dev->dead)
+               goto out_unlock;
+