2022-03-31 15:39:38

by Xiaomeng Tong

Subject: [PATCH v2] opp: use list iterator only inside the loop

To move the list iterator variable into the list_for_each_entry_*()
macro in the future it should be avoided to use the list iterator
variable after the loop body.

To *never* use the list iterator variable after the loop it was
concluded to use a separate dedicated pointer variable [1].

In this case, use a new variable 'iter' as the list iterator, while
use the old variable 'new_dev' as a dedicated pointer to point to the
found entry. And BUG_ON(!new_dev);.

[1]: https://lore.kernel.org/all/CAHk-=wgRr_D8CB-D9Kg-c=EHreAsk5SqXPwr9Y7k9sA6cWXJ6w@mail.gmail.com/

Signed-off-by: Xiaomeng Tong <[email protected]>
---

changes since v1:
- use BUG_ON(!new_dev); instead of return; (Viresh Kumar)

v1: https://lore.kernel.org/lkml/[email protected]/

---
drivers/opp/debugfs.c | 10 +++++++---
1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/drivers/opp/debugfs.c b/drivers/opp/debugfs.c
index 596c185b5dda..81b2bc4b5f43 100644
--- a/drivers/opp/debugfs.c
+++ b/drivers/opp/debugfs.c
@@ -187,14 +187,18 @@ void opp_debug_register(struct opp_device *opp_dev, struct opp_table *opp_table)
static void opp_migrate_dentry(struct opp_device *opp_dev,
struct opp_table *opp_table)
{
- struct opp_device *new_dev;
+ struct opp_device *new_dev = NULL, *iter;
const struct device *dev;
struct dentry *dentry;

/* Look for next opp-dev */
- list_for_each_entry(new_dev, &opp_table->dev_list, node)
- if (new_dev != opp_dev)
+ list_for_each_entry(iter, &opp_table->dev_list, node)
+ if (iter != opp_dev) {
+ new_dev = iter;
break;
+ }
+
+ BUG_ON(!new_dev);

/* new_dev is guaranteed to be valid here */
dev = new_dev->dev;
--
2.17.1

2022-04-12 04:30:05

by Viresh Kumar

Subject: Re: [PATCH v2] opp: use list iterator only inside the loop

On 31-03-22, 16:30, Xiaomeng Tong wrote:
> To move the list iterator variable into the list_for_each_entry_*()
> macro in the future it should be avoided to use the list iterator
> variable after the loop body.
>
> To *never* use the list iterator variable after the loop it was
> concluded to use a separate dedicated pointer variable [1].
>
> In this case, use a new variable 'iter' as the list iterator, while
> use the old variable 'new_dev' as a dedicated pointer to point to the
> found entry. And BUG_ON(!new_dev);.
>
> [1]: https://lore.kernel.org/all/CAHk-=wgRr_D8CB-D9Kg-c=EHreAsk5SqXPwr9Y7k9sA6cWXJ6w@mail.gmail.com/
>
> Signed-off-by: Xiaomeng Tong <[email protected]>
> ---

Applied. Thanks.

--
viresh