add new system file

hc

2024-02-20 102a0743326a03cd1a1202ceda21e175b7d3575c

 kernel/drivers/iommu/iommu.c
..
..
@@ -201,13 +201,23 @@
201
201
 	const struct iommu_ops *ops = dev->bus->iommu_ops;
202
202
 	struct iommu_device *iommu_dev;
203
203
 	struct iommu_group *group;
204
+	static DEFINE_MUTEX(iommu_probe_device_lock);
204
205
 	int ret;
205
206
 
206
207
 	if (!ops)
207
208
 		return -ENODEV;
208
-
209
-	if (!dev_iommu_get(dev))
210
-		return -ENOMEM;
209
+	/*
210
+	 * Serialise to avoid races between IOMMU drivers registering in
211
+	 * parallel and/or the "replay" calls from ACPI/OF code via client
212
+	 * driver probe. Once the latter have been cleaned up we should
213
+	 * probably be able to use device_lock() here to minimise the scope,
214
+	 * but for now enforcing a simple global ordering is fine.
215
+	 */
216
+	mutex_lock(&iommu_probe_device_lock);
217
+	if (!dev_iommu_get(dev)) {
218
+		ret = -ENOMEM;
219
+		goto err_unlock;
220
+	}
211
221
 
212
222
 	if (!try_module_get(ops->owner)) {
213
223
 		ret = -EINVAL;
..
..
@@ -227,11 +237,14 @@
227
237
 		ret = PTR_ERR(group);
228
238
 		goto out_release;
229
239
 	}
230
-	iommu_group_put(group);
231
240
 
241
+	mutex_lock(&group->mutex);
232
242
 	if (group_list && !group->default_domain && list_empty(&group->entry))
233
243
 		list_add_tail(&group->entry, group_list);
244
+	mutex_unlock(&group->mutex);
245
+	iommu_group_put(group);
234
246
 
247
+	mutex_unlock(&iommu_probe_device_lock);
235
248
 	iommu_device_link(iommu_dev, dev);
236
249
 
237
250
 	return 0;
..
..
@@ -244,6 +257,9 @@
244
257
 
245
258
 err_free:
246
259
 	dev_iommu_free(dev);
260
+
261
+err_unlock:
262
+	mutex_unlock(&iommu_probe_device_lock);
247
263
 
248
264
 	return ret;
249
265
 }
..
..
@@ -1766,10 +1782,10 @@
1766
1782
 		return ret;
1767
1783
 
1768
1784
 	list_for_each_entry_safe(group, next, &group_list, entry) {
1785
+		mutex_lock(&group->mutex);
1786
+
1769
1787
 		/* Remove item from the list */
1770
1788
 		list_del_init(&group->entry);
1771
-
1772
-		mutex_lock(&group->mutex);
1773
1789
 
1774
1790
 		/* Try to allocate default domain */
1775
1791
 		probe_alloc_default_domain(bus, group);