Messages in this thread | | | Date | Wed, 15 May 2013 11:47:42 +0200 (CEST) | From | Thomas Gleixner <> | Subject | Re: [patch 07/15] clocksource: Provide unbind interface in sysfs |
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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
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