Re: [KJ] [PATCH] include KERN_* constant in printk() calls in

[Matthew Wilcox <matthew@wil.cx>]

On Mon, Apr 09, 2007 at 04:02:09PM -0400, Dave Jones wrote:
>  > --- a/mm/slab.c
>  > +++ b/mm/slab.c
>  > @@ -1732,9 +1732,9 @@ static void dump_line(char *data, int offset, int limit)
>  >  			error = data[offset + i];
>  >  			bad_count++;
>  >  		}
>  > -		printk(" %02x", (unsigned char)data[offset + i]);
>  > +		printk(KERN_ERR " %02x", (unsigned char)data[offset + i]);
>  >  	}
> 
> This one is wrong.  It's printing a bunch of numbers in a loop, so with your change
> it'll print for example...
> 
> KERN_ERR 00 KERN_ERR 01 KERN_ERR 02 KERN_ERR etc etc..
> 
> you only want the KERN_ERR at the beginning of each line.

Another point is that if you have two CPUs calling printk, the output
can get interleaved if you don't print everything in one go.  If you
come across something like this (printing things in a loop), it's a good
idea to take a hard look at it and see if you can see a way to do it
without the loop so you can print everything on one line.

You can see one example of this here:
http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=blobdiff;f=drivers/scsi/scsi_scan.c;h\x180399406510917111b7580dfc8f3a5f1ce7d95d;hp^[d92b9b46d9ccc5209103beb59cfb75ccafdb5d;hbOf36718ede26ee2da73f2dae94d71e2b06845fc;hpb\08cd5bbfb4763322837cd1f7c621f02ebe22fef

I don't see a clean way to fix this one up, to be honest.  I think it
has to be left as a loop.
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