Messages in this thread | | | Date | Tue, 23 Nov 2010 22:33:44 +0000 | From | Russell King - ARM Linux <> | Subject | Re: About multi-line printk and the need (not) to repeat loglevel markers [Was: Re: [PATCH] ARM: mx3/pcm037: properly allocate memory for mx3-camera] |
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On Wed, Nov 24, 2010 at 07:16:06AM +0900, Linus Torvalds wrote: > No. The KERN_WARNING in the middle of a string is always totally > bogus. There is no "should be". It's just wrong. > > The "\n" is added automatically iff there is a log-level marker at the > beginning of the string (with LOG_CONT being the exception). So > > printk("foo bar baz "); > printk(KERN_WARNING "fiz\n"); > > should output two lines ("foo bar baz" with the default loglevel, and > "fiz" with KERN_WARNING). Even though there is no explicit "\n" there > for the first one. > > But KERN_XYZ anywhere but in the beginning of the string do not > matter. Adding newlines changes none of that. It doesn't make the > marker beginning of the string, it just makes it beginning of the > line.
Oh dear.
Note that KERN_foo in the middle of strings, even after a newline are preserved in the output. So:
printk(KERN_WARNING "BUG: Your driver calls ioremap() on system memory. This leads\n" KERN_WARNING "to architecturally unpredictable behaviour on ARMv6+, and ioremap()\n" KERN_WARNING "will fail in the next kernel release. Please fix your driver.\n");
results in <4>'s appearing on the console. I've always written code over the last 15 years assuming that after any newline in printk output, the log level gets reset and so needs a new log level specifier.
Sounds like this is something which needs auditing as a result of your change, and sounds like its something that kernelnewbies people could do. My own greps haven't revealed any cases though.
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