linux-kernel - Re: checkpatch and kernel/sched.c

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Message-ID: <20071001064448.GA4239@elte.hu>
Date:	Mon, 1 Oct 2007 08:44:48 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Andy Whitcroft <apw@...dowen.org>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org
Subject: Re: checkpatch and kernel/sched.c


(lkml Cc:-ed - this might be of interest to others too)

* Andy Whitcroft <apw@...dowen.org> wrote:

> WARNING: EXPORT_SYMBOL(foo); should immediately follow its function/variable
> #411: FILE: home/apw/git/linux-2.6/kernel/sched.c:408:
> +EXPORT_SYMBOL_GPL(cpu_clock);

yes, this is a legit warning and i fix it every time i see it. (I cannot 
fix this one now because mainline does not have an EXPORT_SYMBOL_GPL for 
cpu_clock(), it's added in -mm? But i cannot find it in mm either. I'll 
fix it once i find the patch :)

> WARNING: printk() should include KERN_ facility level
> #4838: FILE: home/apw/git/linux-2.6/kernel/sched.c:4835:
> +	printk("%-13.13s %c", p->comm,
> 
> WARNING: printk() should include KERN_ facility level
> #5622: FILE: home/apw/git/linux-2.6/kernel/sched.c:5619:
> +				printk("\n");
> 
> WARNING: printk() should include KERN_ facility level
> #5633: FILE: home/apw/git/linux-2.6/kernel/sched.c:5630:
> +				printk("\n");
> 
> WARNING: printk() should include KERN_ facility level
> #5640: FILE: home/apw/git/linux-2.6/kernel/sched.c:5637:
> +			printk(" %s", str);
> 
> These are actually only in debug code and so are unimportant, but 
> technically they are wrong.  This check is a very difficult one in the 
> face of these constructs.  But in this case I think it has got the 
> report right.

this is actually a false positive - as the debug code constructs a 
printk output _without_ \n. So the script should check whether there's 
any \n in the printk string - if there is none, do not emit a warning. 
(if you implement that then i think it can remain a warning and does not 
need to move to CHECK.)

> At this point _if_ we took an error we would not have _DEBUG open and so
> a start would be required, otherwise not.
> 
>                         printk(" %s", str);
> 
> To be 100% correct I assume it would need to have a 
> printk(KERN_DEBUG); after each of the KERN_ERR printk's.

i've fixed this in my tree. But i dont think checkpatch.pl notices this 
level of bug - it just detects the missing KERN_ prefix in printk(), 
right?

> WARNING: braces {} are not necessary for single statement blocks
> #5706: FILE: home/apw/git/linux-2.6/kernel/sched.c:5703:
> +	if (parent->groups == parent->groups->next) {
> +		pflags &= ~(SD_LOAD_BALANCE |
> +				SD_BALANCE_NEWIDLE |
> +				SD_BALANCE_FORK |
> +				SD_BALANCE_EXEC |
> +				SD_SHARE_CPUPOWER |
> +				SD_SHARE_PKG_RESOURCES);
> +	}
> 
> Ok, this one is "correct" at least for the rules as I have them.
> Perhaps the message should not be emitted for very long blocks?

If a statement is not single-line, then braces _are_ fine. Where does 
CodingStyle say that it's not fine?

> WARNING: no space between function name and open parenthesis '('
> #5768: FILE: home/apw/git/linux-2.6/kernel/sched.c:5765:
> +__setup ("isolcpus=", isolated_cpu_setup);
> 
> Almost all other instances of __setup do not have a space, so I assume
> this is a reasonable report.

yes. I have just fixed it in my tree.

> WARNING: externs should be avoided in .c files
> #6545: FILE: home/apw/git/linux-2.6/kernel/sched.c:6542:
> +	extern char __sched_text_start[], __sched_text_end[];
> 
> That one ... dunno.  This check is a difficult one.  Should it be a 
> CHECK?

no, this is a legitimate warning - externs in .c files should move into 
the proper .h file. So i'd suggest to keep this a WARNING.

there are a few other valid warnings that checkpatch.pl emits: such as 
the kfree one - i fixed that too in sched.c.

(Could you send me the v11-to-be version of checkpatch.pl so that i can 
check the remaining issues?)

	Ingo
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