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SubjectRe: [PATCH 0/6] loglevel=pci:8,acpi:8,apic=8 support v5

* Alexey Dobriyan <> wrote:

> On Wed, Sep 17, 2008 at 12:10:09AM -0700, Yinghai Lu wrote:
> > v4: fix some checkpatch error and warning
> > v5: add default with DEFINE_LOGLEVE_SETUP_DEF
> >
> > usage:
> > in .h to have
> > #define KERN_PCI "<pci>"
> > in .c to have
> > then could use
> > printk(KERN_DEBUG KERN_PCI fmt, ...);
> > and command line
> > loglevel=3,pci:8
> >
> > you can add different printk to different files of one subsys if you like
> > not just one susbsys one tag, and don't need to update kernel.h to add more tags
> I think all of this is overdesigned and stupid.
> People expecting that loglevels are exactly right so they can calm
> messages are like security-savvy people who expect all security
> relevant bugfixes carry CVE tag.
> grep says there are 50757 printk calls, only 32129 of them carry KERN_
> tag.
> Oh, and new and improved logs:
> [ 0.340326] pci 0000:00:01.0: PME# supported from D0 D3hot D3cold
> [ 0.340326] pci 0000:00:01.0: PME# disabled
> [ 0.340326] <pci>PCI: 0000:00:1a.0 reg 20 io port: [dc00, dc1f]
> [ 0.340413] <pci>PCI: 0000:00:1a.1 reg 20 io port: [e000, e01f]
> [ 0.340549] <pci>PCI: 0000:00:1a.7 reg 10 32bit mmio: [febffc00, febfffff]
> ^^^^^^^^^
> How this can be an improvement for those who boot with ignore_loglevel,
> I don't know.

the subsystem tags should be cut out by dmesg by default, just like the
normal <1> tags are cut out.

about your general point: it's valid observations. The idea would be to
end this never ending unstable conflict of people adding printks for
debug reasons versus people removing printks who'd like to have a nice
looking bootup log.

Both point of views are correct in different usecases - and IMO the best
solution is the consolidation hpa suggested and what Yinghai is working
towards: to replace all the current ad-hoc debug printouts (with
different switchlets strewn all across the kernel) with an ASCII based
generic printk facility and a generic boot line option.

people adding printks without any KERN_ tag is fine - this facility is
only interesting to subsystems who'd like to make use of it. (core code,
ec. - the items that have a disproportionate weight in terms of system
stability, and which thus have a disproportionate need to stay
debuggable and regression-free)

[ and we also need a dynamic facility to change the filters via debugfs
btw - it should be possible to modify these printk filters after
bootup, runtime. Many subsystems have debug printks that make sense to
enable/disable after the system has booted up. ]

and it's bad and a showstopper if the default output of 'dmesg'
degrades, like your noticed - those are bugs in the concept and need to
be fixed.


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