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.law...@inria.fr> --- drivers/media/usb/tm6000/tm6000-core.c | 24 +++++++++--------------- 1 file changed, 9 insertions(+), 15 deletions(-) diff --git a/drivers/media/usb/tm6000/tm6000-core.c b/drivers/media/usb/tm6000/tm6000-core.c index 2c72370..5c8cbc5 100644 --- a/drivers/media/usb/tm6000/tm6000-core.c +++ b/drivers/media/usb/tm6000/tm6000-core.c @@ -853,11 +853,9 @@ int tm6000_call_fillbuf(struct tm6000_core *dev, enum tm6000_ops_type type, /* FIXME: tm6000_extension_devlist_lock should be a spinlock */ - if (!list_empty(&tm6000_extension_devlist)) { - list_for_each_entry(ops, &tm6000_extension_devlist, next) { - if (ops->fillbuf && ops->type == type) - ops->fillbuf(dev, buf, size); - } + list_for_each_entry(ops, &tm6000_extension_devlist, next) { + if (ops->fillbuf && ops->type == type) + ops->fillbuf(dev, buf, size); } return 0; @@ -898,11 +896,9 @@ void tm6000_init_extension(struct tm6000_core *dev) struct tm6000_ops *ops = NULL; mutex_lock(&tm6000_devlist_mutex); - if (!list_empty(&tm6000_extension_devlist)) { - list_for_each_entry(ops, &tm6000_extension_devlist, next) { - if (ops->init) - ops->init(dev); - } + list_for_each_entry(ops, &tm6000_extension_devlist, next) { + if (ops->init) + ops->init(dev); } mutex_unlock(&tm6000_devlist_mutex); } @@ -912,11 +908,9 @@ void tm6000_close_extension(struct tm6000_core *dev) struct tm6000_ops *ops = NULL; mutex_lock(&tm6000_devlist_mutex); - if (!list_empty(&tm6000_extension_devlist)) { - list_for_each_entry(ops, &tm6000_extension_devlist, next) { - if (ops->fini) - ops->fini(dev); - } + list_for_each_entry(ops, &tm6000_extension_devlist, next) { + if (ops->fini) + ops->fini(dev); } mutex_unlock(&tm6000_devlist_mutex); }
