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Message-ID: <YUhbBqTGHX5+y5D5@bismarck.dyn.berto.se>
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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