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@xxxxxxxx> --- 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); }
