lkml.org 
[lkml]   [2013]   [May]   [15]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [patch 07/15] clocksource: Provide unbind interface in sysfs
On Mon, 29 Apr 2013, John Stultz wrote:
> On 04/25/2013 01:31 PM, Thomas Gleixner wrote:
> > With the module refcount held for the current clocksource there is no
> > way to unload the module.
> >
> > Provide a sysfs interface which allows to unbind the clocksource. One
> > could argue that the clocksource override could be (ab)used to do so,
> > but the clocksource override cannot be used from the kernel itself,
> > while an unbind function can be used to programmatically check whether
> > a clocksource can be shutdown or not.
> >
> > The unbind functionality uses the new skip current feature of
> > clocksource_select and verifies that a fallback clocksource has been
> > installed. If the clocksource which should be unbound is the current
> > clocksource and no fallback can be found, unbind returns -EBUSY.
> >
> > This does not support the unbinding of a clocksource which is used as
> > the watchdog clocksource. No point in fostering crappy hardware.
>
> So.. if the clocksource you want to unbind is the highest rated continuous
> clocksource that doesn't need a watchdog (basically what's likely to be in-use
> and required to be unbinded), its likely to be selected as the watchdog
> already.
>
> ie: on a system that has only HPET/ACPI_PM, you can't unbind HPET, since its a
> watchdog.

No. The thing is that I only prevent unbinding if it is used as the
watchdog. In the above HPET/PM scenario both are potential watchdogs,
but w/o a user it's valid to unbind one of them.

What I need to prevent is:

TSC is current clocksource and we only have ACPI_PM as watchdog and
its used. So now you try to unbind ACPI_PM then the TSC would be left
w/o a watchdog instance. That's what I'm preventing. Will reword the
changelog accordingly.

Thanks,

tglx


\
 
 \ /
  Last update: 2013-05-15 13:01    [W:0.200 / U:0.916 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site