Re: [PATCH 1/4] new timeofday core subsystem (v. B1)

[john stultz <johnstul@us.ibm.com>]

On Fri, 2005-06-03 at 01:29 -0600, Frank Sorenson wrote:
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> john stultz wrote:
> > Andrew, All,
> > 	I'm just re-spinning this to resolve a conflict w/ the CPUFREQ changes
> > Linus accepted last night.
> <snip>
> 
> John,
> 
> I have found an issue with these TOD subsystem patches, and I
> think it's only an issue on systems that use CPUFREQ.  Whenever
> the frequency changes, at least some portions of the kernel
> get confused about their notion of time.  Here are some
> example entries from my syslog:
> 
> Jun  3 00:33:40 moebius kernel: [  145.023201] cpufreq-core: target for CPU 0: 800000 kHz, relation 0
> Jun  3 00:33:47 moebius kernel: [  114.838909] cpufreq-core: target for CPU 0: 1000000 kHz, relation 0
> Jun  3 00:33:47 moebius kernel: [  114.838977] freq-table: request for target 1000000 kHz (relation: 0) for cpu 0
> Jun  3 00:33:47 moebius kernel: [   92.161872] codec_semaphore: semaphore is not ready [0x1][0x700300]
> Jun  3 00:33:52 moebius kernel: [   97.433279] cpufreq-core: target for CPU 0: 1200000 kHz, relation 0
> Jun  3 00:33:58 moebius kernel: [   66.352233] cpufreq-core: target for CPU 0: 1400000 kHz, relation 0
> Jun  3 00:34:08 moebius kernel: [   85.547260] cpufreq-core: target for CPU 0: 1200000 kHz, relation 0
> Jun  3 00:34:16 moebius kernel: [  211.791738] cpufreq-core: target for CPU 0: 800000 kHz, relation 0
> Jun  3 00:34:27 moebius kernel: [  112.941898] cpufreq-core: target for CPU 0: 1000000 kHz, relation 0
> Jun  3 00:34:31 moebius kernel: [  231.793121] cpufreq-core: target for CPU 0: 800000 kHz, relation 0
> Jun  3 00:34:41 moebius kernel: [  147.122593] cpufreq-core: target for CPU 0: 1200000 kHz, relation 0
> Jun  3 00:34:42 moebius kernel: [  123.906802] cpufreq-core: target for CPU 0: 1000000 kHz, relation 0
> Jun  3 00:34:46 moebius kernel: [  251.342116] cpufreq-core: target for CPU 0: 800000 kHz, relation 0
> Jun  3 00:34:51 moebius kernel: [  192.985214] cpufreq-core: target for CPU 0: 1000000 kHz, relation 0
> 
> The printk times are taken from sched_clock(), which now
> varies depending on the cpu frequency.  Without these patches,
> the printk times appear to consistently increase at the right rate.
> I'm not sure what other portions of the kernel are affected by
> this (watchdogs firing, or other issues?).

Yep, looks like something isn't right between sched_clock and the
cpufreq changes. I'll let you know when I've sorted it out.

Thanks for the great testing!
-john

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