On Tue, 2019-08-27 at 19:55 +0300, Denis Efremov wrote:
> IS_ERR, IS_ERR_OR_NULL, IS_ERR_VALUE already contain unlikely optimization
> internally. Thus, there is no point in calling these functions under
> likely/unlikely.
>
> This check is based on the coccinelle rule developed by Enrico Weigelt
> https://lore.kernel.org/lkml/[email protected]/
[]
> diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
[]
> @@ -6480,6 +6480,13 @@ sub process {
> "Using $1 should generally have parentheses around
> the comparison\n" . $herecurr);
> }
>
> +# nested likely/unlikely calls
> + if ($perl_version_ok &&
> + $line =~
> /\b(?:(?:un)?likely)\s*\(!?\s*(IS_ERR(?:_OR_NULL|_VALUE)?)\s*${balanced_parens}\s*\)/)
> {
> + WARN("LIKELY_MISUSE",
> + "nested (un)?likely calls, unlikely already used
> in $1 internally\n" . $herecurr);
> + }
> +
Couple things:
1:
Are you going to submit patches for the just 10 instances that exist?
$ git grep -P -n
'\b(?:(?:un)?likely)\s*\(!?\s*(IS_ERR(?:_OR_NULL|_VALUE)?)\s*\([^\)]+\)\s*\)'
arch/x86/kernel/irq.c:246: if (likely(!IS_ERR_OR_NULL(desc))) {
drivers/infiniband/hw/hfi1/verbs.c:1044: if
(unlikely(IS_ERR_OR_NULL(pbuf))) {
drivers/input/mouse/alps.c:1479: } else if
(unlikely(IS_ERR_OR_NULL(priv->dev3))) {
fs/ntfs/mft.c:74: if (likely(!IS_ERR(page))) {
fs/ntfs/mft.c:157: if (likely(!IS_ERR(m)))
fs/ntfs/mft.c:274: if (likely(!IS_ERR(m))) {
fs/ntfs/mft.c:1779: if (likely(!IS_ERR(rl2)))
fs/ntfs/namei.c:118: if (likely(!IS_ERR(dent_inode))) {
fs/ntfs/runlist.c:954: if (likely(!IS_ERR(old_rl)))
include/net/udp.h:483: if (unlikely(IS_ERR_OR_NULL(segs))) {
2:
This will not warn about code like:
fs/ntfs/mft.c: if (unlikely(IS_ERR(rl) || !rl->length || rl->lcn < 0)) {
that could probably be better written as:
if (IS_ERR(rl) || unlikely(!rl->length || rl->lcn < 0)) {
