Messages in this thread | | | Subject | Re: [PATCH] checkpatch: check for nested (un)?likely calls | From | Joe Perches <> | Date | Tue, 27 Aug 2019 10:21:01 -0700 |
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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/1559767582-11081-1-git-send-email-info@metux.net/ [] > 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)) {
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