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Date: Mon, 20 Sep 2021 11:57:26 +0200 From: Niklas Söderlund <niklas.soderlund@...igine.com> To: Joe Perches <joe@...ches.com> Cc: Andy Whitcroft <apw@...onical.com>, linux-kernel@...r.kernel.org Subject: Re: False positive for 'Possible unnecessary KERN_ERR' warning in checkpatch Hi Joe, Thanks for your help. I like your solution. Would you like to send a patch for this or would you like me to do that with you in a Suggested-by ? On 2021-09-15 20:46:22 -0700, Joe Perches wrote: > On Tue, 2021-09-14 at 18:05 +0200, Niklas Söderlund wrote: > > 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. > > > > I would have avoided it and gotten dynamic debug support at the > same time with: > --- > drivers/net/ethernet/netronome/nfp/nfp_net.h | 48 ++++++++++++++-------------- > 1 file changed, 24 insertions(+), 24 deletions(-) > > diff --git a/drivers/net/ethernet/netronome/nfp/nfp_net.h b/drivers/net/ethernet/netronome/nfp/nfp_net.h > index df203738511bf..46178a7244ad8 100644 > --- a/drivers/net/ethernet/netronome/nfp/nfp_net.h > +++ b/drivers/net/ethernet/netronome/nfp/nfp_net.h > @@ -25,32 +25,32 @@ > > #include "nfp_net_ctrl.h" > > -#define nn_pr(nn, lvl, fmt, args...) \ > - ({ \ > - struct nfp_net *__nn = (nn); \ > +#define nn_pr(nn, lvl, fmt, ...) \ > +({ \ > + struct nfp_net *__nn = (nn); \ > \ > - if (__nn->dp.netdev) \ > - netdev_printk(lvl, __nn->dp.netdev, fmt, ## args); \ > - else \ > - dev_printk(lvl, __nn->dp.dev, "ctrl: " fmt, ## args); \ > - }) > - > -#define nn_err(nn, fmt, args...) nn_pr(nn, KERN_ERR, fmt, ## args) > -#define nn_warn(nn, fmt, args...) nn_pr(nn, KERN_WARNING, fmt, ## args) > -#define nn_info(nn, fmt, args...) nn_pr(nn, KERN_INFO, fmt, ## args) > -#define nn_dbg(nn, fmt, args...) nn_pr(nn, KERN_DEBUG, fmt, ## args) > - > -#define nn_dp_warn(dp, fmt, args...) \ > - ({ \ > - struct nfp_net_dp *__dp = (dp); \ > + if (__nn->dp.netdev) \ > + netdev_##lvl(__nn->dp.netdev, fmt, ##__VA_ARGS__); \ > + else \ > + dev_##lvl(__nn->dp.dev, "ctrl: " fmt, ##__VA_ARGS__); \ > +}) > + > +#define nn_err(nn, fmt, ...) nn_pr(nn, err, fmt, ##__VA_ARGS__) > +#define nn_warn(nn, fmt, ...) nn_pr(nn, warn, fmt, ##__VA_ARGS__) > +#define nn_info(nn, fmt, ...) nn_pr(nn, info, fmt, ##__VA_ARGS__) > +#define nn_dbg(nn, fmt, ...) nn_pr(nn, dbg, fmt, ##__VA_ARGS__) > + > +#define nn_dp_warn(dp, fmt, ...) \ > +({ \ > + struct nfp_net_dp *__dp = (dp); \ > \ > - if (unlikely(net_ratelimit())) { \ > - if (__dp->netdev) \ > - netdev_warn(__dp->netdev, fmt, ## args); \ > - else \ > - dev_warn(__dp->dev, fmt, ## args); \ > - } \ > - }) > + if (unlikely(net_ratelimit())) { \ > + if (__dp->netdev) \ > + netdev_warn(__dp->netdev, fmt, ##__VA_ARGS__); \ > + else \ > + dev_warn(__dp->dev, fmt, ##__VA_ARGS__); \ > + } \ > +}) > > /* Max time to wait for NFP to respond on updates (in seconds) */ > #define NFP_NET_POLL_TIMEOUT 5 > > -- Regards, Niklas Söderlund
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