| Message ID | 1529904187-18673-3-git-send-email-kernelfans@gmail.com (mailing list archive) |
|---|---|
| State | New, archived |
| Delegated to: | Bjorn Helgaas |
| Headers | show |
[ 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
---
0-DAY kernel test infrastructure Open Source Technology Center
https://lists.01.org/pipermail/kbuild-all Intel Corporation
Hi Dan, Thanks for your hints, see the comment in lines. On Tue, Jun 26, 2018 at 3:44 PM Dan Carpenter <dan.carpenter@oracle.com> wrote: > > [ 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? > Yes, you are right. > 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... > Yes, if list_empty, then the code can not touch ret. But ret is useless in this scene. Does it matter? Thanks and regards, Pingfan > 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 > > --- > 0-DAY kernel test infrastructure Open Source Technology Center > https://lists.01.org/pipermail/kbuild-all Intel Corporation
On Wed, Jun 27, 2018 at 10:34:54AM +0800, Pingfan Liu wrote: > > 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... > > > Yes, if list_empty, then the code can not touch ret. But ret is > useless in this scene. Does it matter? > I'm not sure I understand what you're asking? Of course, it matters? regards, dan carpenter
On Wed, Jun 27, 2018 at 4:35 PM Dan Carpenter <dan.carpenter@oracle.com> wrote: > > On Wed, Jun 27, 2018 at 10:34:54AM +0800, Pingfan Liu wrote: > > > 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... > > > > > Yes, if list_empty, then the code can not touch ret. But ret is > > useless in this scene. Does it matter? > > > > I'm not sure I understand what you're asking? Of course, it matters? > Oh, I misunderstood your original comment. Yes, you are right. I will fix it in next version, if this code section is still used. Thanks and regards, Pingfan
diff --git a/drivers/base/base.h b/drivers/base/base.h index a75c302..37f86ca 100644 --- a/drivers/base/base.h +++ b/drivers/base/base.h @@ -135,6 +135,7 @@ extern void device_unblock_probing(void); /* /sys/devices directory */ extern struct kset *devices_kset; +extern int device_reorder_consumer(struct device *dev); extern void devices_kset_move_last(struct device *dev); #if defined(CONFIG_MODULES) && defined(CONFIG_SYSFS) diff --git a/drivers/base/core.c b/drivers/base/core.c index 8113d2c..db30e86 100644 --- a/drivers/base/core.c +++ b/drivers/base/core.c @@ -161,6 +161,103 @@ static bool is_consumer(struct device *query, struct device *supplier) return false; } +/* recursively move the potential consumers in open section (left, right) + * after the barrier + */ +static int __device_reorder_consumer(struct device *consumer, + struct list_head *left, struct list_head *right, + struct pos_info *p) +{ + struct list_head *iter; + struct device *c_dev, *s_dev, *tail_dev; + + descendants_reorder_after_pos(consumer, p); + tail_dev = p->tail; + /* (left, right) may contain consumers, hence checking if any moved + * child serving as supplier. The reversing order help us to meet + * the last supplier of a consumer. + */ + list_opensect_for_each_reverse(iter, left, right) { + struct list_head *l_iter, *moved_left, *moved_right; + + moved_left = (&consumer->kobj.entry)->prev; + moved_right = tail_dev->kobj.entry.next; + /* the moved section may contain potential suppliers */ + list_opensect_for_each_reverse(l_iter, moved_left, + moved_right) { + s_dev = list_entry(l_iter, struct device, kobj.entry); + c_dev = list_entry(iter, struct device, kobj.entry); + /* to fix: this poses extra effort for locking */ + if (is_consumer(c_dev, s_dev)) { + p->tail = NULL; + /* to fix: lock issue */ + p->pos = s_dev; + /* reorder after the last supplier */ + __device_reorder_consumer(c_dev, + l_iter, right, p); + } + } + } + return 0; +} + +static int find_last_supplier(struct device *dev, struct device *supplier) +{ + struct device_link *link; + + list_for_each_entry_reverse(link, &dev->links.suppliers, c_node) { + if (link->supplier == supplier) + return 1; + } + if (dev == supplier) + return -1; + return 0; +} + +/* When reodering, take care of the range of (old_pos(dev), new_pos(dev)), + * there may be requirement to recursively move item. + */ +int device_reorder_consumer(struct device *dev) +{ + struct list_head *iter, *left, *right; + struct device *cur_dev; + struct pos_info info; + int ret, idx; + + idx = device_links_read_lock(); + if (list_empty(&dev->links.suppliers)) { + device_links_read_unlock(idx); + return 0; + } + spin_lock(&devices_kset->list_lock); + list_for_each_prev(iter, &devices_kset->list) { + cur_dev = list_entry(iter, struct device, kobj.entry); + ret = find_last_supplier(dev, cur_dev); + switch (ret) { + case -1: + goto unlock; + case 1: + break; + case 0: + continue; + } + } + BUG_ON(!ret); + + /* record the affected open section */ + left = dev->kobj.entry.prev; + right = iter; + info.pos = list_entry(iter, struct device, kobj.entry); + info.tail = NULL; + /* dry out the consumers in (left,right) */ + __device_reorder_consumer(dev, left, right, &info); + +unlock: + spin_unlock(&devices_kset->list_lock); + device_links_read_unlock(idx); + return 0; +} + static int device_reorder_to_tail(struct device *dev, void *not_used) { struct device_link *link;
commit 52cdbdd49853 ("driver core: correct device's shutdown order") introduces supplier<-consumer order in devices_kset. The commit tries to cleverly maintain both parent<-child and supplier<-consumer order by reordering a device when probing. This method makes things simple and clean, but unfortunately, breaks parent<-child order in some case, which is described in next patch in this series. Here this patch tries to resolve supplier<-consumer by only reordering a device when it has suppliers, and takes care of the following scenario: [consumer, children] [ ... potential ... ] supplier ^ ^ After moving the consumer and its children after the supplier, the potentail section may contain consumers whose supplier is inside children, and this poses the requirement to dry out all consumpers in the section recursively. Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: Grygorii Strashko <grygorii.strashko@ti.com> Cc: Christoph Hellwig <hch@infradead.org> Cc: Bjorn Helgaas <helgaas@kernel.org> Cc: Dave Young <dyoung@redhat.com> Cc: linux-pci@vger.kernel.org Cc: linuxppc-dev@lists.ozlabs.org Signed-off-by: Pingfan Liu <kernelfans@gmail.com> --- drivers/base/base.h | 1 + drivers/base/core.c | 97 +++++++++++++++++++++++++++++++++++++++++++++++++++++ 2 files changed, 98 insertions(+)