[PATCH 0/7] drop unnecessary list_empty

[PATCH 0/7] drop unnecessary list_empty

[Julia Lawall]

The various list iterators are able to handle an empty list.
The only effect of avoiding the loop is not initializing some
index variables.
Drop list_empty tests in cases where these variables are not
used.

The semantic patch that makes these changes is as follows:
(http://coccinelle.lip6.fr/)

<smpl>
@@
expression x,e;
iterator name list_for_each_entry;
statement S;
identifier i;
@@

-if (!(list_empty(x))) {
   list_for_each_entry(i,x,...) S
- }
 ... when != i
? i = e

@@
expression x,e;
iterator name list_for_each_entry_safe;
statement S;
identifier i,j;
@@

-if (!(list_empty(x))) {
   list_for_each_entry_safe(i,j,x,...) S
- }
 ... when != i
     when != j
(
  i = e;
|
? j = e;
)

@@
expression x,e;
iterator name list_for_each;
statement S;
identifier i;
@@

-if (!(list_empty(x))) {
   list_for_each(i,x) S
- }
 ... when != i
? i = e

@@
expression x,e;
iterator name list_for_each_safe;
statement S;
identifier i,j;
@@

-if (!(list_empty(x))) {
   list_for_each_safe(i,j,x) S
- }
 ... when != i
     when != j
(
  i = e;
|
? j = e;
)

// -------------------

@@
expression x,e;
statement S;
identifier i;
@@

-if (!(list_empty(x)))
   list_for_each_entry(i,x,...) S
 ... when != i
? i = e

@@
expression x,e;
statement S;
identifier i,j;
@@

-if (!(list_empty(x)))
   list_for_each_entry_safe(i,j,x,...) S
 ... when != i
     when != j
(
  i = e;
|
? j = e;
)

@@
expression x,e;
statement S;
identifier i;
@@

-if (!(list_empty(x)))
   list_for_each(i,x) S
 ... when != i
? i = e

@@
expression x,e;
statement S;
identifier i,j;
@@

-if (!(list_empty(x)))
   list_for_each_safe(i,j,x) S
 ... when != i
     when != j
(
  i = e;
|
? j = e;
)
</smpl>

---

 drivers/media/pci/saa7134/saa7134-core.c                      |   14 ++---
 drivers/media/usb/cx231xx/cx231xx-core.c                      |   16 ++----
 drivers/media/usb/tm6000/tm6000-core.c                        |   24 +++-------
 drivers/net/ethernet/mellanox/mlx5/core/steering/dr_matcher.c |   13 ++---
 drivers/net/ethernet/mellanox/mlx5/core/steering/dr_rule.c    |    5 --
 drivers/net/ethernet/sfc/ptp.c                                |   20 +++-----
 drivers/net/wireless/ath/dfs_pattern_detector.c               |   15 ++----
 sound/soc/intel/atom/sst/sst_loader.c                         |   10 +---
 sound/soc/intel/skylake/skl-pcm.c                             |    8 +--
 sound/soc/intel/skylake/skl-topology.c                        |    5 --
 10 files changed, 53 insertions(+), 77 deletions(-)

[PATCH 7/7] ath: drop unnecessary list_empty

[Julia Lawall]

list_for_each_entry{_safe} is able to handle an empty list.
The only effect of avoiding the loop is not initializing the
index variable.
Drop list_empty tests in cases where these variables are not
used.

Note that list_for_each_entry{_safe} is defined in terms of
list_first_entry, which indicates that it should not be used on an
empty list.  But in list_for_each_entry{_safe}, the element obtained
by list_first_entry is not really accessed, only the address of its
list_head field is compared to the address of the list head, so the
list_first_entry is safe.

The semantic patch that makes this change for the list_for_each_entry
case is as follows: (http://coccinelle.lip6.fr/)

<smpl>
@@
expression x,e;
statement S;
identifier i;
@@

-if (!(list_empty(x)))
   list_for_each_entry(i,x,...) S
 ... when != i
? i = e
</smpl>

Signed-off-by: Julia Lawall <Julia.Lawall@inria.fr>

---
 drivers/net/wireless/ath/dfs_pattern_detector.c |   15 ++++++---------
 1 file changed, 6 insertions(+), 9 deletions(-)

diff --git a/drivers/net/wireless/ath/dfs_pattern_detector.c b/drivers/net/wireless/ath/dfs_pattern_detector.c
index a274eb0..0813473 100644
--- a/drivers/net/wireless/ath/dfs_pattern_detector.c
+++ b/drivers/net/wireless/ath/dfs_pattern_detector.c
@@ -253,17 +253,15 @@ static void channel_detector_exit(struct dfs_pattern_detector *dpd,
 static void dpd_reset(struct dfs_pattern_detector *dpd)
 {
 	struct channel_detector *cd;
-	if (!list_empty(&dpd->channel_detectors))
-		list_for_each_entry(cd, &dpd->channel_detectors, head)
-			channel_detector_reset(dpd, cd);
+	list_for_each_entry(cd, &dpd->channel_detectors, head)
+		channel_detector_reset(dpd, cd);
 
 }
 static void dpd_exit(struct dfs_pattern_detector *dpd)
 {
 	struct channel_detector *cd, *cd0;
-	if (!list_empty(&dpd->channel_detectors))
-		list_for_each_entry_safe(cd, cd0, &dpd->channel_detectors, head)
-			channel_detector_exit(dpd, cd);
+	list_for_each_entry_safe(cd, cd0, &dpd->channel_detectors, head)
+		channel_detector_exit(dpd, cd);
 	kfree(dpd);
 }
 
@@ -331,9 +329,8 @@ static bool dpd_set_domain(struct dfs_pattern_detector *dpd,
 		return false;
 
 	/* delete all channel detectors for previous DFS domain */
-	if (!list_empty(&dpd->channel_detectors))
-		list_for_each_entry_safe(cd, cd0, &dpd->channel_detectors, head)
-			channel_detector_exit(dpd, cd);
+	list_for_each_entry_safe(cd, cd0, &dpd->channel_detectors, head)
+		channel_detector_exit(dpd, cd);
 	dpd->radar_spec = rt->radar_types;
 	dpd->num_radar_types = rt->num_radar_types;
 

Re: [PATCH 0/7] drop unnecessary list_empty

[Mark Brown]

On Sun, 26 Jul 2020 12:58:25 +0200, Julia Lawall wrote:
> The various list iterators are able to handle an empty list.
> The only effect of avoiding the loop is not initializing some
> index variables.
> Drop list_empty tests in cases where these variables are not
> used.
> 
> The semantic patch that makes these changes is as follows:
> (http://coccinelle.lip6.fr/)
> 
> [...]

Applied to

   https://git.kernel.org/pub/scm/linux/kernel/git/broonie/sound.git for-next

Thanks!

[1/1] ASoC: Intel: drop unnecessary list_empty
      commit: a383308e50244a28fe927b9c1acbe0a963bf186b

All being well this means that it will be integrated into the linux-next
tree (usually sometime in the next 24 hours) and sent to Linus during
the next merge window (or sooner if it is a bug fix), however if
problems are discovered then the patch may be dropped or reverted.

You may get further e-mails resulting from automated or manual testing
and review of the tree, please engage with people reporting problems and
send followup patches addressing any issues that are reported if needed.

If any updates are required or you are submitting further changes they
should be sent as incremental updates against current git, existing
patches will not be replaced.

Please add any relevant lists and maintainers to the CCs when replying
to this mail.

Thanks,
Mark

Re: [PATCH 7/7] ath: drop unnecessary list_empty

[Kalle Valo]

Julia Lawall <Julia.Lawall@inria.fr> wrote:

> list_for_each_entry{_safe} is able to handle an empty list.
> The only effect of avoiding the loop is not initializing the
> index variable.
> Drop list_empty tests in cases where these variables are not
> used.
> 
> Note that list_for_each_entry{_safe} is defined in terms of
> list_first_entry, which indicates that it should not be used on an
> empty list.  But in list_for_each_entry{_safe}, the element obtained
> by list_first_entry is not really accessed, only the address of its
> list_head field is compared to the address of the list head, so the
> list_first_entry is safe.
> 
> The semantic patch that makes this change for the list_for_each_entry
> case is as follows: (http://coccinelle.lip6.fr/)
> 
> <smpl>
> @@
> expression x,e;
> statement S;
> identifier i;
> @@
> 
> -if (!(list_empty(x)))
>    list_for_each_entry(i,x,...) S
>  ... when != i
> ? i = e
> </smpl>
> 
> Signed-off-by: Julia Lawall <Julia.Lawall@inria.fr>
> Signed-off-by: Kalle Valo <kvalo@codeaurora.org>

Patch applied to ath-next branch of ath.git, thanks.

18c25b4019ca ath: drop unnecessary list_empty

-- 
https://patchwork.kernel.org/patch/11685677/

https://wireless.wiki.kernel.org/en/developers/documentation/submittingpatches