Re: [PATCH 2/9] ext4: Use pr_fmt and pr_<level>
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On Tue, 20 Mar 2012 03:10:01 EDT, David Miller said: > From: Valdis.Kletnieks@xxxxxx > Date: Tue, 20 Mar 2012 01:46:06 -0400 > > > OK. Say I'm a scraper. How do I distinguish between: > > > > pr_info("foo"); > > printk(KERN_INFO "foo"); > > > > Oh my. seems that both result in exactly the same thing ending up in the > > dmesg buffer > > No it doesn't result in the same output, read the definitions again. > > pr_info can be influenced by pr_fmt, plain printk cannot So if nobody screws around with a #define pr_fmt, you can't tell the difference, and if somebody *does* screw around wiht a #define pr_fmt, you have no good way to know what *this* build of the kernel produces as output without tracking down the actual define in use. Consider Joe Perche's example "you can do things like" - you don't have a good programmatic way to tell what that pr_info() actually outputs, so an actual human is going to have to review that and figure out what needs to be pattern-matched. Not a situation you want to be in if you're a scraper. At least the perf subsystem is nice enough to *tell* you "I've added an extra field you may not know about" and provides a mechanism to skip over it. And I can see why Ted doesn't want to have code churn to do a half-assed conversion, when there will just be *more* churn if and when we ever get off our collective butts and deploy a structured solution.
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