[Cuis-dev] ATTENTION. maybe nasty bug in Time management on Summer/Winter time change

[Nicola Mingotti]

Hi Juan,

Thank you for your changes !

I am getting married on day 20 Nov, I guess will not be able to put the 
necessary attention
level to this subject as I should, at least in the short period. Sorry 
about it, I have risen the issue
It should be my duty to follow it closely up to resolution. Also, i 
think it is a very important subject.

In the last days I had some private communications with Bruce and Dave 
(in CC), i report
a very short summary here since it might be useful for further development.

----- executive summary -------

We checked the status of the matter in Squeak, which has progressed in 
this respect in recent times.

1] After and experiment made by Bruce on MST/MDT time change we are 
confident the code
in Squeak is able keep "the date updated" on Daylight time change, 
automatically. GOOD !

2] If one changes the time zone manually, Squeak can't detect it. One 
must call the primitive
`Time primitiveUpdateTimeZone.` . In my opinion this is much less 
important than point [1].

3] Dave knows very well the new Squeak implementation

----------------------------------------

I will try to do some experiments myself as soon as i can !


Bye
Nicola








On 11/9/21 22:19, Juan Vuletich wrote:
> After comments from Gerald (below) and Dave (at the opensmalltalk-vm 
> issue you opened), this is my take.
>
> This touches a rather basic area of the system, so any bug could 
> affect a lot of code. Folks, please, review.
>
> Thanks,
>
> On 11/3/2021 1:08 PM, Nicola Mingotti via Cuis-dev wrote:
>>
>> I put it here:
>> https://github.com/OpenSmalltalk/opensmalltalk-vm/issues/602
>>
>> bye
>> Nicola
>>
>>
>>
>>
>> On 11/3/21 16:51, Nicola Mingotti wrote:
>>>
>>> Hi Gerald !
>>>
>>> thank you for looking into it !
>>>
>>> for me this is still too much above my head, I have
>>> not tweaked the VM up to now, and this seems a central subject
>>> that should be taken care by somebody who understands well
>>> the possible consequences of a change.
>>>
>>> I am going to forward the problem to the vm mailing list.
>>>
>>> bye
>>> Nicola
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>> On 11/3/21 12:05, Gerald Klix wrote:
>>>> Nicola,
>>>>
>>>> If you look at
>>>>
>>>> https://github.com/OpenSmalltalk/opensmalltalk-vm/blob/634e4e3c8556a72d54f43beefc3069c60e594a21/platforms/unix/vm/sqUnixHeartbeat.c#L139 
>>>>
>>>>
>>>> you see that "vmGMTOffset" is added to the new time.
>>>> "vmGMTOffset" is updated here:
>>>>
>>>> https://github.com/OpenSmalltalk/opensmalltalk-vm/blob/634e4e3c8556a72d54f43beefc3069c60e594a21/platforms/unix/vm/sqUnixHeartbeat.c#L150 
>>>>
>>>>
>>>> which is only called during VM initialization:
>>>>
>>>> https://github.com/OpenSmalltalk/opensmalltalk-vm/blob/634e4e3c8556a72d54f43beefc3069c60e594a21/platforms/unix/vm/sqUnixHeartbeat.c#L273 
>>>>
>>>>
>>>>
>>>> All this is only an educated guess.
>>>>
>>>>
>>>> HTH, Gerald
>>>>
>>>>
>>>> PS: This is really nasty, it may also ignore leap seconds:
>>>>
>>>> https://github.com/OpenSmalltalk/opensmalltalk-vm/blob/634e4e3c8556a72d54f43beefc3069c60e594a21/platforms/unix/vm/sqUnixHeartbeat.c#L135 
>>>>
>>>>
>>>>
>>>> On 11/3/21 10:56 AM, Nicola Mingotti via Cuis-dev wrote:
>>>>>
>>>>> Hi guys,
>>>>>
>>>>> I report you what i discovered this morning.
>>>>>
>>>>> . I have 2 services running in Cuis in 2 independent Linux/Debian 
>>>>> servers.
>>>>>
>>>>> . In weekend in Italy we changed time from CEST to CET
>>>>>
>>>>> . The OSes changed time correctly
>>>>>
>>>>> . But Cuis services are 1 hour forward !?!?
>>>>>
>>>>> . If i run a fresh new Cuis now in my laptop (Linux/debian vm), I 
>>>>> see it has the correct time, corresponding to the OS time
>>>>>
>>>>> . I did not change my localTimeZone in Cuis, in any machine. It is 
>>>>> acceptable for me it says UTC
>>>>>    even if it is actually localtime.
>>>>>
>>>>> . Seeing 'DateAndTime now' I discovered that Cuis by default uses 
>>>>> primLocalMicrosecondClock, so it should
>>>>>    always use the OS local clock and think it is in the UTC 
>>>>> timezone. But, it is not doing
>>>>>    so on images that were started some days ago (max 20). It does 
>>>>> so on new run images.
>>>>>
>>>>> I don't know well how to fix this. Maybe some time config is made 
>>>>> when Cuis starts up?
>>>>> It seems it is remembering the time when it was stared.
>>>>>
>>>>>
>>>>> EXTRA. NOT IMPORTANT AS THE PREVIOUS.
>>>>> If there are some changes to make I have a suggestion for 
>>>>> improvement.
>>>>> Could we set localTimeZone to "system", or "local" ? At present we 
>>>>> are reading localTime from the OS
>>>>> and setting to UTC. Which is a bit confusing.
>>>>>
>>>>> bye
>>>>> Nicola
>>>>>
>>>>>
>>>>>
>>>>>
>>>
>>
>
>
> -- 
> Juan Vuletich
> www.cuis-smalltalk.org
> https://github.com/Cuis-Smalltalk/Cuis-Smalltalk-Dev
> https://github.com/jvuletich
> https://www.linkedin.com/in/juan-vuletich-75611b3
> @JuanVuletich
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.cuis.st/mailman/archives/cuis-dev/attachments/20211110/00d6e7a4/attachment.htm>