linux-kernel - Re: [PATCH] WARN(): add a \n to the message printk

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Message-ID: <20090615185326.GA6057@nowhere>
Date:	Mon, 15 Jun 2009 20:53:28 +0200
From:	Frederic Weisbecker <fweisbec@...il.com>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Arjan van de Ven <arjan@...radead.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Alan Cox <alan@...rguk.ukuu.org.uk>
Subject: Re: [PATCH] WARN(): add a \n to the message printk

On Mon, Jun 15, 2009 at 10:57:15AM -0700, Linus Torvalds wrote:
> 
> 
> On Mon, 15 Jun 2009, Linus Torvalds wrote:
> > 
> > NOTE! This is, of course, totally untested. And we're bound to have 
> > continuation printk's that don't have the KERN_CONT at front, and need 
> > them added, but I think this is generally a saner model than what we have 
> > now, or your suggested explicit addition of '\n'.
> 
> Ok, it's tested now.
> 
> It works, and yes, it does show cases of insanity: both missing KERN_CONT 
> (common), and _extra_ KERN_CONT (odd).
> 
> For example, the ACPI printk's seem to have pointless KERN_CONT's in them, 
> an I get printouts like:
> 
> 	[    0.000000] <c>ACPI: RSDP 00000000000fe020 00024 (v02 INTEL )
> 	[    0.000000] <c>ACPI: XSDT 00000000bf7fe120 0006C (v01 INTEL  DX58SO   0000084F      01000013)
> 	[    0.000000] <c>ACPI: FACP 00000000bf7fd000 000F4 (v03 INTEL  DX58SO   0000084F MSFT 0100000D)
> 	...
> 
> where that "<c>" is just because ACPI does something odd and pointless.
> 
> The lack of KERN_CONT shows up in printouts like
> 
> 	[   26.626492] CPU: L1 I cache: 32K
> 	[   26.626492] , L1 D cache: 32K
> 	...
> 	[   26.826201] ACPI: (supports S0
> 	[   26.826243]  S5
> 	[   26.826326] )
> 	...
> 	[   26.839617] ACPI: PCI Interrupt Link [LNKA] (IRQs
> 	[   26.839660]  3
> 	[   26.839741]  4
> 	[   26.839823]  5
> 	[   26.839904]  6
> 	[   26.839985]  7
> 	[   26.840067]  9
> 	[   26.840148]  10
> 	[   26.840230]  *11
> 	[   26.840313]  12
> 	[   26.840395]  14
> 	[   26.840476]  15
> 	[   26.840558] )
> 	...
> 	[   26.964999] ACPI: CPU0 (power states:
> 	[   26.965040]  C1[C1]
> 	[   26.965123]  C2[C3]
> 	[   26.965205] )
> 	...
> 	[   27.231268] ata_piix 0000:00:1f.5: MAP [
> 	[   27.231309]  P0
> 	[   27.231390]  --
> 	[   27.231472]  P1
> 	[   27.231553]  --
> 	[   27.231635]  ]
> 	...
> 	[   28.092534]  sda:
> 	[   28.092820]  sda1
> 	[   28.092910]  sda2
> 	...
> 
> where the kernel now added a newline because they were separate printk's 
> and didn't have KERN_CONT on the continuation.
> 
> But despite seeing these kinds of things, I do think the patch is the 
> right thing to do. It just shows that since KERN_CONT didn't use to _do_ 
> anything, people obviously mis-used it. It's the old "if it wasn't tested, 
> it's buggy" thing, but none of these look in the least like serious 
> problems to the approach.
> 
> Comments? We could make it remove the unnecessary '<c>' things (so that 
> you can always add KERN_CONT if you _want_ to), but the patch as-is will 
> show them because I think it's useful to see them. 
> 
> 			Linus

Nice, eventually KERN_CONT have now a real sense.
IMHO it's good to keep <c> in the beginning of the line for misuses like
ACPI does. It provides easy and quick checks to find them.

Frederic.

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