Messages in this thread | | | Date | Thu, 4 Jul 2013 12:27:28 +0200 (CEST) | From | Thomas Gleixner <> | Subject | Re: [PATCH 1/3] clocksource: clean up clocksource_select |
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On Thu, 4 Jul 2013, Alex Shi wrote: > > We need this check and it is completely unrelated to the problem > > you're trying to solve. > > > > Assume the following: > > > > System boots with clocksource A and switches into highres mode. > > Now clocksource B gets registered and B is not highres capable. > > > > clocksource_find_best() selects again A, but we have > > clocksource=B on the kernel command line to override the kernel > > decision. > > > > By removing the check, you install he non highres capable clocksource > > B and kill the machine. > > > > You'r right. my bad, Sorry! > > BTW, why we allow user override a second best clocksource? I mean user > can override the tsc with hpet. because undetected unstable tsc?
The user can decide to override with clocksource=jiffies if he wants for testing purposes. That wont switch into highres ever if done from the kernel command line. Now we have a sysfs interface, so we need to sanity check the user override against highres.
The override is quite useful to test hpet, pmtimer on a machine which would always select TSC.
Thanks,
tglx
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