| Message ID | 20190829165025.15750-1-efremov@linux.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v3,01/11] checkpatch: check for nested (un)?likely() calls | expand |
> +# nested likely/unlikely calls > + if ($line =~ /\b(?:(?:un)?likely)\s*\(\s*!?\s*(IS_ERR(?:_OR_NULL|_VALUE)?|WARN)/) { > + WARN("LIKELY_MISUSE", How do you think about to use the specification “(?:IS_ERR(?:_(?:OR_NULL|VALUE))?|WARN)” in this regular expression? Regards, Markus
On 31.08.2019 12:15, Markus Elfring wrote: >> +# nested likely/unlikely calls >> + if ($line =~ /\b(?:(?:un)?likely)\s*\(\s*!?\s*(IS_ERR(?:_OR_NULL|_VALUE)?|WARN)/) { >> + WARN("LIKELY_MISUSE", > > How do you think about to use the specification “(?:IS_ERR(?:_(?:OR_NULL|VALUE))?|WARN)” > in this regular expression? Hmm, (?: <- Catch group is required here, since it is used in diagnostic message, see $1 IS_ERR (?:_ <- Another atomic group just to show that '_' is a common prefix? I'm not sure about this. Usually, Perl interpreter is very good at optimizing such things. You could see this optimization if you run perl with -Mre=debug. (?:OR_NULL|VALUE))?|WARN) Regards, Denis
>>> +# nested likely/unlikely calls >>> + if ($line =~ /\b(?:(?:un)?likely)\s*\(\s*!?\s*(IS_ERR(?:_OR_NULL|_VALUE)?|WARN)/) { >>> + WARN("LIKELY_MISUSE", >> >> How do you think about to use the specification “(?:IS_ERR(?:_(?:OR_NULL|VALUE))?|WARN)” >> in this regular expression? … > IS_ERR > (?:_ <- Another atomic group just to show that '_' is a common prefix? Yes. - I hope that this specification detail can help a bit. > Usually, Perl interpreter is very good at optimizing such things. Would you like to help this software component by omitting a pair of non-capturing parentheses at the beginning? \b(?:un)?likely\s* Regards, Markus
On 31.08.2019 19:45, Markus Elfring wrote: >>>> +# nested likely/unlikely calls >>>> + if ($line =~ /\b(?:(?:un)?likely)\s*\(\s*!?\s*(IS_ERR(?:_OR_NULL|_VALUE)?|WARN)/) { >>>> + WARN("LIKELY_MISUSE", >>> >>> How do you think about to use the specification “(?:IS_ERR(?:_(?:OR_NULL|VALUE))?|WARN)” >>> in this regular expression? > … >> IS_ERR >> (?:_ <- Another atomic group just to show that '_' is a common prefix? > > Yes. - I hope that this specification detail can help a bit. I'm not sure that another pair of brackets for a single char worth it. >> Usually, Perl interpreter is very good at optimizing such things. The interpreter optimizes it internally: echo 'IS_ERR_OR_NULL' | perl -Mre=debug -ne '/IS_ERR(?:_OR_NULL|_VALUE)?/ && print' Compiling REx "IS_ERR(?:_OR_NULL|_VALUE)?" Final program: 1: EXACT <IS_ERR> (4) 4: CURLYX[0]{0,1} (16) 6: EXACT <_> (8) <-- common prefix 8: TRIE-EXACT[OV] (15) <OR_NULL> <VALUE> ... > > Would you like to help this software component by omitting a pair of > non-capturing parentheses at the beginning? > > \b(?:un)?likely\s* This pair of brackets is required to match "unlikely" and it's optional in order to match "likely". Regards, Denis
>>>>> +# nested likely/unlikely calls >>>>> + if ($line =~ /\b(?:(?:un)?likely)\s*\(\s*!?\s*(IS_ERR(?:_OR_NULL|_VALUE)?|WARN)/) { >>>>> + WARN("LIKELY_MISUSE", … >> \b(?:un)?likely\s* > > This pair of brackets is required to match "unlikely" > and it's optional in order to match "likely". I agree also to this view if you refer to the shortened regular expression here. But I got an other development opinion for an extra pair of non-capturing parentheses at the front (from the version which you suggested). Regards, Markus
diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl index 93a7edfe0f05..56969ce06df4 100755 --- a/scripts/checkpatch.pl +++ b/scripts/checkpatch.pl @@ -6480,6 +6480,12 @@ sub process { "Using $1 should generally have parentheses around the comparison\n" . $herecurr); } +# nested likely/unlikely calls + if ($line =~ /\b(?:(?:un)?likely)\s*\(\s*!?\s*(IS_ERR(?:_OR_NULL|_VALUE)?|WARN)/) { + WARN("LIKELY_MISUSE", + "nested (un)?likely() calls, $1 already uses unlikely() internally\n" . $herecurr); + } + # whine mightly about in_atomic if ($line =~ /\bin_atomic\s*\(/) { if ($realfile =~ m@^drivers/@) {
IS_ERR(), IS_ERR_OR_NULL(), IS_ERR_VALUE() and WARN*() already contain unlikely() optimization internally. Thus, there is no point in calling these functions and defines 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/ Signed-off-by: Denis Efremov <efremov@linux.com> Cc: Joe Perches <joe@perches.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Andy Whitcroft <apw@canonical.com> --- scripts/checkpatch.pl | 6 ++++++ 1 file changed, 6 insertions(+)