From: Julia Lawall <Julia.Lawall@inria.fr>
To: Mauro Carvalho Chehab <mchehab@kernel.org>
Cc: kernel-janitors@vger.kernel.org, linux-media@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: [PATCH 3/7] [media] cx231xx: drop unnecessary list_empty
Date: Sun, 26 Jul 2020 12:58:28 +0200 [thread overview]
Message-ID: <1595761112-11003-4-git-send-email-Julia.Lawall@inria.fr> (raw)
In-Reply-To: <1595761112-11003-1-git-send-email-Julia.Lawall@inria.fr>
list_for_each_entry 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 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, 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 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
</smpl>
Signed-off-by: Julia Lawall <Julia.Lawall@inria.fr>
---
drivers/media/usb/cx231xx/cx231xx-core.c | 16 ++++++----------
1 file changed, 6 insertions(+), 10 deletions(-)
diff --git a/drivers/media/usb/cx231xx/cx231xx-core.c b/drivers/media/usb/cx231xx/cx231xx-core.c
index 982cb56e..05d91ca 100644
--- a/drivers/media/usb/cx231xx/cx231xx-core.c
+++ b/drivers/media/usb/cx231xx/cx231xx-core.c
@@ -115,11 +115,9 @@ void cx231xx_init_extension(struct cx231xx *dev)
struct cx231xx_ops *ops = NULL;
mutex_lock(&cx231xx_devlist_mutex);
- if (!list_empty(&cx231xx_extension_devlist)) {
- list_for_each_entry(ops, &cx231xx_extension_devlist, next) {
- if (ops->init)
- ops->init(dev);
- }
+ list_for_each_entry(ops, &cx231xx_extension_devlist, next) {
+ if (ops->init)
+ ops->init(dev);
}
mutex_unlock(&cx231xx_devlist_mutex);
}
@@ -129,11 +127,9 @@ void cx231xx_close_extension(struct cx231xx *dev)
struct cx231xx_ops *ops = NULL;
mutex_lock(&cx231xx_devlist_mutex);
- if (!list_empty(&cx231xx_extension_devlist)) {
- list_for_each_entry(ops, &cx231xx_extension_devlist, next) {
- if (ops->fini)
- ops->fini(dev);
- }
+ list_for_each_entry(ops, &cx231xx_extension_devlist, next) {
+ if (ops->fini)
+ ops->fini(dev);
}
mutex_unlock(&cx231xx_devlist_mutex);
}
next prev parent reply other threads:[~2020-07-26 11:40 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-26 10:58 [PATCH 0/7] drop unnecessary list_empty Julia Lawall
2020-07-26 10:58 ` Julia Lawall [this message]
2020-07-26 10:58 ` [PATCH 5/7] [media] saa7134: " Julia Lawall
2020-07-26 10:58 ` [PATCH 6/7] [media] tm6000: " Julia Lawall
2020-07-30 22:28 ` [PATCH 0/7] " Mark Brown
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