scst: Remove the dev_unregistering member variable

This variable is no longer needed because devices are
removed from the devices list via list_del_init() before
being unregistered. See also trunk r5510 / commit f3820d5bc4.

Signed-off-by: Bart Van Assche <bart.vanassche@sandisk.com>

scst/include/scst.h

@@ -2523,14 +2523,6 @@ struct scst_device {
 	/* Set, if a strictly serialized cmd is waiting blocked */
 	unsigned int strictly_serialized_cmd_waiting:1;
 
-	/*
-	 * Set, if this device is being unregistered. Useful to let sysfs
-	 * attributes know when they should exit immediately to prevent
-	 * possible deadlocks with their device unregistration waiting for
-	 * their kobj last put.
-	 */
-	unsigned int dev_unregistering:1;
-
 	/**************************************************************/
 
 	/*************************************************************

scst/src/dev_handlers/scst_vdisk.c

@@ -7426,6 +7426,17 @@ static ssize_t vdisk_sysfs_rotational_show(struct kobject *kobj,
 	return pos;
 }
 
+static bool scst_dev_being_unregistered(struct scst_device *dev)
+{
+	bool res;
+
+	mutex_lock(&scst_mutex);
+	res = list_empty(&dev->dev_list_entry);
+	mutex_unlock(&scst_mutex);
+
+	return res;
+}
+
 static int vdev_sysfs_process_get_filename(struct scst_sysfs_work_item *work)
 {
 	int res = 0;
@@ -7443,7 +7454,7 @@ static int vdev_sysfs_process_get_filename(struct scst_sysfs_work_item *work)
 	 * under scst_vdisk_mutex.
 	 */
 	while (!mutex_trylock(&scst_vdisk_mutex)) {
-		if (dev->dev_unregistering) {
+		if (scst_dev_being_unregistered(dev)) {
 			TRACE_MGMT_DBG("Skipping being unregistered dev %s",
 				dev->virt_name);
 			res = -ENOENT;
@@ -7454,18 +7465,6 @@ static int vdev_sysfs_process_get_filename(struct scst_sysfs_work_item *work)
 			goto out_put;
 		}
 		msleep(100);
-		/*
-		 * We need to reread dev_unregistering from memory, hence
-		 * prevent compiler from putting it in a register. Generally,
-		 * it shouldn't happen, because the compiler isn't allowed to do
-		 * such a transformation if any functions that can cause side
-		 * effects are called between successive accesses, but let's be
-		 * on the safe side. We can't cast dev_unregistering to
-		 * volatile, because it has no effect we need, and can't cast
-		 * it to *(volatile bool*)&, because it isn't possible to get
-		 * address of a bit field.
-		 */
-		barrier();
 	}
 
 	virt_dev = dev->dh_priv;

scst/src/scst_main.c

@@ -1266,8 +1266,6 @@ static void scst_unregister_device(struct scsi_device *scsidp)
 		goto out_unlock;
 	}
 
-	dev->dev_unregistering = 1;
-
 	list_del_init(&dev->dev_list_entry);
 
 	scst_dg_dev_remove_by_dev(dev);
@@ -1531,8 +1529,6 @@ void scst_unregister_virtual_device(int id)
 		goto out_unlock;
 	}
 
-	dev->dev_unregistering = 1;
-
 	list_del_init(&dev->dev_list_entry);
 
 	scst_pr_clear_dev(dev);