Re: set_rtc_time() cleanup / normalization

In message [ref]
Eugene Surovegin wrote:

quoted

The consensus so far seems to be that we shouldn't call set_rtc_time
in the timer interrupt handler.  Is anyone willing to speak up with a
reason why we should keep it?

Because there are systems which rely on this behavior?
For example, all our embedded systems use this feature.

Wolfgang said that "... many embedded systems run in a configuration
where they use a high precision RTC chip...".

All embedded systems I saw used cheap RTC parts with poor accuracy.

I think we mix two different issues here:

1) call set_rtc_time() from timer interrupt every 11 min if clock is
synched (e.g. by NTP)
    I don't see any problems with this.

There are many problems with this approch, for a summary see
http://lists.linuxppc.org/linuxppc-dev/200305/msg00034.html

The main reason to remove it is thatit's broken (i. e. causes  kernel
crashes) on many hardware configurations.

2) set_rtc_time() implementation for concrete RTC device *maybe* slow or
just cannot
    be called from the interrupt context.
    Why just don't fix actual RTC code in each case ?
    It may be useful to provide some *generic* facility for such cases.

Do you have any recommendation HOW to implement such a "fix"?

The argument to put the set_rtc_time() call into the timer  interrupt
was  accuracy;  if  you  have to remove it from interrupt context the
only solution I've seen so far is to pay  for  an  additional  kernel
thread - more overhead, and you just removed the only argument to put
it into the timer interrupt at all.

It just makes no sense to me.

Best regards,

Wolfgang Denk

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