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

[Frank Sorenson <frank@tuxrocks.com>]

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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?).

Thanks,

Frank
- -- 
Frank Sorenson - KD7TZK
Systems Manager, Computer Science Department
Brigham Young University
frank@tuxrocks.com
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