Re: [PATCH 2/3] drivers/base: reorder consumer and its children behind suppliers

From: Dan Carpenter
Date: Tue Jun 26 2018 - 03:45:37 EST


[ There is a bug with kbuild where it's not showing the Smatch warnings
but I can probably guess... - dan ]

Hi Pingfan,

Thank you for the patch! Perhaps something to improve:

url: https://github.com/0day-ci/linux/commits/Pingfan-Liu/drivers-base-bugfix-for-supplier-consumer-ordering-in-device_kset/20180625-132702


# https://github.com/0day-ci/linux/commit/1b2a1e63898baf80e8e830991284e1534bc54766
git remote add linux-review https://github.com/0day-ci/linux
git remote update linux-review
git checkout 1b2a1e63898baf80e8e830991284e1534bc54766
vim +/ret +245 drivers/base/core.c

1b2a1e63 Pingfan Liu 2018-06-25 216
1b2a1e63 Pingfan Liu 2018-06-25 217 /* When reodering, take care of the range of (old_pos(dev), new_pos(dev)),
1b2a1e63 Pingfan Liu 2018-06-25 218 * there may be requirement to recursively move item.
1b2a1e63 Pingfan Liu 2018-06-25 219 */
1b2a1e63 Pingfan Liu 2018-06-25 220 int device_reorder_consumer(struct device *dev)
1b2a1e63 Pingfan Liu 2018-06-25 221 {
1b2a1e63 Pingfan Liu 2018-06-25 222 struct list_head *iter, *left, *right;
1b2a1e63 Pingfan Liu 2018-06-25 223 struct device *cur_dev;
1b2a1e63 Pingfan Liu 2018-06-25 224 struct pos_info info;
1b2a1e63 Pingfan Liu 2018-06-25 225 int ret, idx;
1b2a1e63 Pingfan Liu 2018-06-25 226
1b2a1e63 Pingfan Liu 2018-06-25 227 idx = device_links_read_lock();
1b2a1e63 Pingfan Liu 2018-06-25 228 if (list_empty(&dev->links.suppliers)) {
1b2a1e63 Pingfan Liu 2018-06-25 229 device_links_read_unlock(idx);
1b2a1e63 Pingfan Liu 2018-06-25 230 return 0;
1b2a1e63 Pingfan Liu 2018-06-25 231 }
1b2a1e63 Pingfan Liu 2018-06-25 232 spin_lock(&devices_kset->list_lock);
1b2a1e63 Pingfan Liu 2018-06-25 233 list_for_each_prev(iter, &devices_kset->list) {
1b2a1e63 Pingfan Liu 2018-06-25 234 cur_dev = list_entry(iter, struct device, kobj.entry);
1b2a1e63 Pingfan Liu 2018-06-25 235 ret = find_last_supplier(dev, cur_dev);
1b2a1e63 Pingfan Liu 2018-06-25 236 switch (ret) {
1b2a1e63 Pingfan Liu 2018-06-25 237 case -1:
1b2a1e63 Pingfan Liu 2018-06-25 238 goto unlock;
1b2a1e63 Pingfan Liu 2018-06-25 239 case 1:
1b2a1e63 Pingfan Liu 2018-06-25 240 break;
1b2a1e63 Pingfan Liu 2018-06-25 241 case 0:
1b2a1e63 Pingfan Liu 2018-06-25 242 continue;

The break breaks from the switch and the continue continues the loop so
they're equivalent. Perhaps you intended to break from the loop?

1b2a1e63 Pingfan Liu 2018-06-25 243 }
1b2a1e63 Pingfan Liu 2018-06-25 244 }
1b2a1e63 Pingfan Liu 2018-06-25 @245 BUG_ON(!ret);

If the list is empty then "ret" can be unitialized. We test a different
list "dev->links.suppliers" to see if that's empty. I wrote a bunch of
code to make Smatch try to understand about empty lists, but I don't
think it works...

1b2a1e63 Pingfan Liu 2018-06-25 246
1b2a1e63 Pingfan Liu 2018-06-25 247 /* record the affected open section */
1b2a1e63 Pingfan Liu 2018-06-25 248 left = dev->kobj.entry.prev;
1b2a1e63 Pingfan Liu 2018-06-25 249 right = iter;
1b2a1e63 Pingfan Liu 2018-06-25 250 info.pos = list_entry(iter, struct device, kobj.entry);
1b2a1e63 Pingfan Liu 2018-06-25 251 info.tail = NULL;
1b2a1e63 Pingfan Liu 2018-06-25 252 /* dry out the consumers in (left,right) */
1b2a1e63 Pingfan Liu 2018-06-25 253 __device_reorder_consumer(dev, left, right, &info);
1b2a1e63 Pingfan Liu 2018-06-25 254
1b2a1e63 Pingfan Liu 2018-06-25 255 unlock:
1b2a1e63 Pingfan Liu 2018-06-25 256 spin_unlock(&devices_kset->list_lock);
1b2a1e63 Pingfan Liu 2018-06-25 257 device_links_read_unlock(idx);
1b2a1e63 Pingfan Liu 2018-06-25 258 return 0;
1b2a1e63 Pingfan Liu 2018-06-25 259 }
1b2a1e63 Pingfan Liu 2018-06-25 260

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