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Forum Topic - Shutdown Message isn't printed in console on QNX 7.0: (10 Items)

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Marcos Pedrazzini

08/06/2024 8:23 AM

post122577

Shutdown Message isn't printed in console on QNX 7.0

we try with the following configuration and wdt disable and there wasn´t any dump or trace on serial console

[image=0x10800000] 
[virtual=armle-v7,raw +compress] .bootstrap = {
	startup-imx6x-apalis -m -vvvvv  
	[+keeplinked]
	kdumper
    PATH=/proc/boot:/bin:/usr/bin:/opt/bin/sbin:/usr/sbin LD_LIBRARY_PATH=/proc/boot:/lib:/usr/lib:/lib/dll:/lib/dll/pci

:/opt/lib procnto-smp-instr -v
}

thanks.

Elad Lahav

08/06/2024 8:25 AM

post122578

Re: Shutdown Message isn't printed in console on QNX 7.0

There wouldn't be any message if it's a watchdog reset. The hardware resets the processor without involving the OS at 
all.
If the board supports it you can install a watchdog interrupt handler, though that still won't (by itself) cause a 
shutdown message.

--Elad

Marcos Pedrazzini

08/06/2024 10:37 AM

post122580

Re: Shutdown Message isn't printed in console on QNX 7.0

> There wouldn't be any message if it's a watchdog reset. The hardware resets 
> the processor without involving the OS at all.
> If the board supports it you can install a watchdog interrupt handler, though 
> that still won't (by itself) cause a shutdown message.
> 
> --Elad

Hi Elad,
The watchdog is disabled, we crash the system forcing a segmentation fault (writing invalid address throw mmap function)
, the qnx kernell stop scheduling but no shutdown message is printed.

Elad Lahav

08/06/2024 10:42 AM

post122581

Re: Shutdown Message isn't printed in console on QNX 7.0

Sorry, I misunderstood. Thought you said it was a watchdog reset.
What do you mean by writing an invalid address through mmap()? I assume you were mapping some physical memory and trying
 to crash the system that way, but it really depends on what address was used. For example, writing to a bank that's not
 powered will often result in a bus lockup.

--Elad

Marcos Pedrazzini

08/06/2024 1:17 PM

post122582

Re: Shutdown Message isn't printed in console on QNX 7.0

> Sorry, I misunderstood. Thought you said it was a watchdog reset.
> What do you mean by writing an invalid address through mmap()? I assume you 
> were mapping some physical memory and trying to crash the system that way, but
>  it really depends on what address was used. For example, writing to a bank 
> that's not powered will often result in a bus lockup.
> 
> --Elad

Exactly , we write invalid address (trying to force a bus lockup, segmentation fault, etc) until QNX scheduler stop 
working (system freeze, no software or hardware reset) , base on  https://www.qnx.com/developers/docs/7.1/#com.qnx.doc.
neutrino.technotes/topic/proc_dump.html , a shutdown message should be printed on serial console, but in this case qnx 
freeze without any message or information.

Elad Lahav

08/06/2024 1:25 PM

post122583

Re: Shutdown Message isn't printed in console on QNX 7.0

You only get a shutdown message if the processor raises an exception while the kernel is executing. If you just get the 
hardware into a bad state there is no guarantee that such an exception will occur. That's what watchdogs are for.

--Elad

Marcos Pedrazzini

08/06/2024 1:41 PM

post122584

Re: Shutdown Message isn't printed in console on QNX 7.0

> You only get a shutdown message if the processor raises an exception while the
>  kernel is executing. If you just get the hardware into a bad state there is 
> no guarantee that such an exception will occur. That's what watchdogs are for.
> 
> 
> --Elad
but, for example if you rise a "data abort exception" in a process (user space), the process is kill and the core dump 
file is generated but the QNX scheduler keeps working, now we found in our system a condition unknow for us at the 
moment where QNX stop scheduling and the system freeze, how can we related this condition to an microcontroller 
exception (like bus lockup, or segmentation fault)?
what about exceptions on kernell space? 
how can we debug this condition?

thanks

Elad Lahav

08/06/2024 1:52 PM

post122585

Re: Shutdown Message isn't printed in console on QNX 7.0

If the hardware stops functioning (such as in the case of a bus lockup) then there is nothing the kernel can do to 
detect this problem, let alone to rectify it. The kernel needs the hardware in order to execute - it's not special in 
this sense. Cases like these require specialized debug facilities such as JTAG and/or an embedded trace buffer (ETB).

--Elad

Marcos Pedrazzini

08/06/2024 2:01 PM

post122586

Re: Shutdown Message isn't printed in console on QNX 7.0

> If the hardware stops functioning (such as in the case of a bus lockup) then 
> there is nothing the kernel can do to detect this problem, let alone to 
> rectify it. The kernel needs the hardware in order to execute - it's not 
> special in this sense. Cases like these require specialized debug facilities 
> such as JTAG and/or an embedded trace buffer (ETB).
> 
> --Elad

thanks Elad, 

In the case of  segmentation fault on an interruption, what´s the kernell behavior?

Elad Lahav

08/06/2024 2:13 PM

post122587

Re: Shutdown Message isn't printed in console on QNX 7.0

If you have an ISR, and it faults, then the fault will be caught, the kernel will display the shutdown message and 
invoke the reboot callout.
One more reason not to use ISRs...

--Elad

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