Messages in this thread | | | Date | Tue, 14 Sep 2021 18:05:12 +0200 | From | Niklas Söderlund <> | Subject | False positive for 'Possible unnecessary KERN_ERR' warning in checkpatch |
| |
Hi Joe,
Maybe you are already aware of this, but in case you are not.
The issue is the checkpatch check for unnecessary KERN_<LEVEL> for log functions. If a single line contains a statement that match a log function name from $logFunctions, such as foo_err() and the same line contains a KERN_<LEVEL> statement the 'WARNING: Possible unnecessary KERN_ERR' is triggered. This is true even if the KERN_<LEVEL> statement is not part of the arguments to the foo_err() definition that triggers the first part of the check.
This can be demonstrated by,
./scripts/checkpatch.pl --mailback --git c821e617896e99b8
Where we get (among others) the warning,
WARNING: Possible unnecessary KERN_ERR #38: FILE: drivers/net/ethernet/netronome/nfp/nfp_net.h:63: +#define nn_err(nn, fmt, args...) nn_pr(nn, KERN_ERR, fmt, ## args)
Looking at the code in checkpatch.pl we have,
our $logFunctions = qr{(?x: printk(?:_ratelimited|_once|_deferred_once|_deferred|)| (?:[a-z0-9]+_){1,2}(?:printk|emerg|alert|crit|err|warning|warn|notice|info|debug|dbg|vdbg|devel|cont|WARN)(?:_ratelimited|_once|)| TP_printk| WARN(?:_RATELIMIT|_ONCE|)| panic| MODULE_[A-Z_]+| seq_vprintf|seq_printf|seq_puts )};
...
# check for logging functions with KERN_<LEVEL> if ($line !~ /printk(?:_ratelimited|_once)?\s*\(/ && $line =~ /\b$logFunctions\s*\(.*\b(KERN_[A-Z]+)\b/) { my $level = $1; if (WARN("UNNECESSARY_KERN_LEVEL", "Possible unnecessary $level\n" . $herecurr) && $fix) { $fixed[$fixlinenr] =~ s/\s*$level\s*//; } }
Looking at the line from above that triggers the warning,
#define nn_err(nn, fmt, args...) nn_pr(nn, KERN_ERR, fmt, ## args)
We see that the warning is triggers by the regexp but that it matches the first part on nn_err( and then the second part of on the second argument to nn_pr, KERN_ERR. I believe this to be a false positive.
Unfortunately my Perl skills are not good enough to fix the check to only look for KERN_[A-Z]+ inside the argument list to the log function name that matches the first part of the regexp.
-- Regards, Niklas Söderlund
| |