Hi!
> > This patch adds coccinelle script for detecting !likely and !unlikely
> > usage. It's better to use unlikely instead of !likely and vice versa.
>
> Please explain _why_ is it better in the changelog.
>
> btw: there are relatively few uses like this in the kernel.
>
> $ git grep -P '!\s*(?:un)?likely\s*\(' | wc -l
> 40
>
> afaict: It may save 2 bytes of x86/64 object code.
>
> For instance:
>
> $ diff -urN kernel/tsacct.lst.old kernel/tsacct.lst.new|less
> --- kernel/tsacct.lst.old 2019-08-25 09:21:39.936570183 -0700
> +++ kernel/tsacct.lst.new 2019-08-25 09:22:20.774324886 -0700
> @@ -24,158 +24,153 @@
> 15: 48 89 fb mov %rdi,%rbx
> u64 time, delta;
>
> - if (!likely(tsk->mm))
> + if (unlikely(tsk->mm))
Are you sure this is equivalent?
Pavel
> 18: 4c 8d ab 28 02 00 00 lea 0x228(%rbx),%r13
> 1f: e8 00 00 00 00 callq 24 <__acct_update_integrals+0x24>
> 20: R_X86_64_PLT32 __sanitizer_cov_trace_pc-0x4
> 24: 4c 89 ef mov %r13,%rdi
> 27: e8 00 00 00 00 callq 2c <__acct_update_integrals+0x2c>
> 28: R_X86_64_PLT32 __asan_load8_noabort-0x4
> - 2c: 4c 8b bb 28 02 00 00 mov 0x228(%rbx),%r15
> - 33: 4d 85 ff test %r15,%r15
> - 36: 74 34 je 6c <__acct_update_integrals+0x6c>
> + 2c: 48 83 bb 28 02 00 00 cmpq $0x0,0x228(%rbx)
> + 33: 00
> + 34: 75 34 jne 6a <__acct_update_integrals+0x6a>
> return;
>
> And here's a possible equivalent checkpatch test.
> ---
> scripts/checkpatch.pl | 18 ++++++++++++++++++
> 1 file changed, 18 insertions(+)
>
> diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
> index 287fe73688f0..364603ad1a47 100755
> --- a/scripts/checkpatch.pl
> +++ b/scripts/checkpatch.pl
> @@ -6529,6 +6529,24 @@ sub process {
> "Using $1 should generally have parentheses around
> the comparison\n" . $herecurr);
> }
>
> +# !(likely|unlikely)(condition) use should be (unlikely|likely)(condition)
> + if ($perl_version_ok &&
> + $line =~ /(\!\s*((?:un)?likely))\s*$balanced_parens/) {
> + my $match = $1;
> + my $type = $2;
> + my $reverse;
> + if ($type eq "likely") {
> + $reverse = "unlikely";
> + } else {
> + $reverse = "likely";
> + }
> + if (WARN("LIKELY_MISUSE",
> + "Prefer $reverse over $match\n" . $herecurr) &&
> + $fix) {
> + $fixed[$fixlinenr] =~
> s/\Q$match\E\s*\(/$reverse(/;
> + }
> + }
> +
> # whine mightly about in_atomic
> if ($line =~ /\bin_atomic\s*\(/) {
> if ($realfile =~ m@^drivers/@) {
>
--
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