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SubjectRe: [PATCH] arm64: Neaten show_regs, remove KERN_CONT
On Mon, Oct 24, 2016 at 09:27:57AM -0700, Joe Perches wrote:
> On Mon, 2016-10-24 at 12:31 +0100, Mark Rutland wrote:
> > On Sun, Oct 23, 2016 at 01:40:49PM -0700, Joe Perches wrote:
> > > commit db4b0710fae9 ("arm64: fix show_regs fallout from KERN_CONT changes")
> > > corrected the KERN_CONT fallout from commit 4bcc595ccd80
> > > ("printk: reinstate KERN_CONT for printing continuation lines"), but
> > > the code still has unnecessary KERN_CONT uses. Remove them.
> >
> > Why are these unnecessary KERN_CONTs a larger problem than duplicating
> > the format string for a third time? Having to duplicate it at all was
> > annoying enough.
>
> Not printing partial lines is the best solution to avoiding
> message output interleaving.

Would you mind mentioning that explicitly in the commit message? That
makes it obvious what the benefit of avoiding KERN_CONT is.

> > Overall, to avoid messing with the KERN_CONT mess it'd be nicer to
> > format this all into a buffer (with the format string only existing the
> > once) and subsequently print it with one printk call
>
> A single printk call would get one timestamp which would
> make for ragged/staggered reading.

That does not appear to be the case; as fr as I can tell the core prints a
timestamp per line as required. If I run:

printk("TEST\nLINE1\nLINE2\nLINE3\nLINE4\n");

... with "printk.time=1", over the UART:

[ 41.201864] TEST
[ 41.201864] LINE1
[ 41.201864] LINE2
[ 41.201864] LINE3
[ 41.201864] LINE4

... with "printk.time=1", via the $(dmesg):

[ 41.201864] TEST
[ 41.201864] LINE1
[ 41.201864] LINE2
[ 41.201864] LINE3
[ 41.201864] LINE4

... with "printk.time=0", over the UART:

TEST
LINE1
LINE2
LINE3
LINE4

... with "printk.time=0", via the $(dmesg):

TEST
LINE1
LINE2
LINE3
LINE4

... with "printk.time=0", via $(dmesg -T):

[Mon Oct 24 17:38:37 2016] TEST
[Mon Oct 24 17:38:37 2016] LINE1
[Mon Oct 24 17:38:37 2016] LINE2
[Mon Oct 24 17:38:37 2016] LINE3
[Mon Oct 24 17:38:37 2016] LINE4

Thanks,
Mark.

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