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QNX Operating System/Discussion/OSTech/System freezes for 48 ms. Trace Event Log shows no events./List of Posts
Forum Topic - System freezes for 48 ms. Trace Event Log shows no events.: (5 Items)
   
Update
Jan Körner
04/24/2019 7:25 AM
post119672
System freezes for 48 ms. Trace Event Log shows no events.   
Hello,

I observed a strange system behavior. The system is a quad core QNX 6.6 system. Main load is on CPU 1 and 2. During 
automatic testing, it sporadically appears that the whole system freezes for about 48 ms. I could catch that time slot 
with tracelogger. It shows that the complete system status is hold for 48 ms. No events are logged, no interrupts are 
coming.
The QNX system time read out via SYSPAGE_ENTRY(qtime) does not run further during that time, but the CPU cycles increase
. Thus I got a difference between QNX system time and CPU cycles (calculated into time).

I attached three pictures of the Trace Event Log:
CpuActivity.png shows that CPU 1 and 2 are at 100% while CPU 3 and 4 are at 0 % during the whole time slot.
TimelineOverview.png shows an overview of all running processes. There are no entries during the 48 ms time slot.
TimelineDetail.png shows the CPU 1 to 4 idle threads and two user threads which are running on CPU 1 and 2. Again there 
are no events in that time. The two user threads run on relatively low priority (30 and 6). Blocking by priority cannot 
be the root cause of the freeze.

Do you have an idea, what may lead to this behavior?

Thanks and regards,
Jan
Attachment: Image CpuActivity.png 100.5 KB Image TimelineDetail.png 22.26 KB Image TimelineOverview.png 55.2 KB
Dennis Kellly
04/24/2019 7:48 AM
post119673
Re: System freezes for 48 ms. Trace Event Log shows no events.   
Assuming this is Intel?

1. Could be SMI stealing time from the o/s: https://en.wikipedia.org/wiki/System_Management_Mode
2. Could be (more likely) bios menu sets some sort of USB "compatibility" mode which periodically polls.

Note two cores don't run during that time (likely one).  The timeline shows two because two cores were running before 
and after control was taken away from the o/s.
Jan Körner
04/24/2019 8:18 AM
post119674
Re: System freezes for 48 ms. Trace Event Log shows no events.   
Yes it is Intel.

It does not look like it is periodic unless the period is very long (couple of seconds or longer).
I am also wondering why this freeze takes so long. My system has to react on high frequency events within ~10 ms.

Your last sentence is right. The system stays where it was before and runs again afterwards. I also had occurrences when
 only CPU 1 had 100 % and all others 0 % because the according idle threads were running before.
Dennis Kellly
04/24/2019 8:22 AM
post119675
Re: System freezes for 48 ms. Trace Event Log shows no events.   
Whatever is happening is outside the control of QNX.  Possibly the system is being put back to "16-bir\t real-mode" 
during which a protected mode o/s cannot receive any interrupts.
Albrecht Uhlmann
04/24/2019 8:25 AM
post119676
Re: System freezes for 48 ms. Trace Event Log shows no events.   
Maybe faulty hardware, OS is caught in a very tight interrupt loop which prevents the timer interrupt and the scheduler 
from running.

-Al

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