Need help: kernel seems to be hanging, but no way to tell

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Need help: kernel seems to be hanging, but no way to tell

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dluberger
Contributor V

I'm stuck at the kernel message "Key type dns_resolver registered".  My SD card appears to be fine, bootloader is fine, I have an image on my LCD, there are no obvious error messages in my boot log (see attached).  I've used multiple file systems -- a minimal build with busybox, a version from buildroot, my own rootfs built with linaro, the demo version that comes with the eval board -- none of that helps. I've done everything I can think of in the the u-boot build and the kernel/device tree to make this all match my custom board; but the kernel always stops at this same point. I actually can't tell if it's hung or if it's actually doing something, but certainly there are no more messages coming out of the console. I've let it run for a few hours and nothing happens.

Can someone give me pointers on how to troubleshoot the kernel? Is there a way to verify whether the kernel has hung or is waiting on something or otherwise actively doing something? I don't know how to find where in the source code the kernel is no longer sending out info to the console, but some kind of progress indicator or note that says what it's waiting on would help.

Also, I've tried disabling most things in the device tree, and I've tried enabling most things. I'm at a complete loss as to what's going on.

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igorpadykov
NXP Employee
NXP Employee

Hi David

from log board uses 512MB abd cma=320MB, one can decrease it to reasonable value

for example add "cma=96M" in uboot cmdline.


Best regards
igor
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igorpadykov
NXP Employee
NXP Employee

Hi David

from log board uses 512MB abd cma=320MB, one can decrease it to reasonable value

for example add "cma=96M" in uboot cmdline.


Best regards
igor
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Note: If this post answers your question, please click the Correct Answer button. Thank you!
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dluberger
Contributor V

I marked this as correct, but adding the cma=96M to the boot command didn't work as the kernel seemed to ignore it (it still displayed "Reserved memory: created CMA memory pool at 0x8c000000, size 320 MiB". So I found in the device tree where this is set and changed it to be 96MiB there, and that seemed to work.  now I'm having new problems related to the SD card and rootfs, but this is definitely progress.

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dluberger
Contributor V

Technically I have a 4GB DDR3L IC for RAM per the reference design, but yes I guess it maxes out at 512MB. I'm not sure I understand what you're suggesting I do though.  I left u-boot almost entirely as it was downloaded from the freescale git. I only changed memory calibration and display settings.  what does the change you suggest do, and how might the current settings be affecting things?

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igorpadykov
NXP Employee
NXP Employee

A deep dive into CMA [LWN.net] 

add "cma=96M" as in attached Release Notes sect.4 Kernel Boot Parameters

Best regards
igor

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dluberger
Contributor V

I'll add that to the parameters, but i don't see anything about CMA In the release notes you attached.  And should i be using kernel version 4.1.15? i see there's a version 4.9 on freescale git.

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igorpadykov
NXP Employee
NXP Employee

you can try any: 4.1.15 or version 4.9, cma kernel boot parameter is described in common

linux documentation

Linux Kernel Parameters 

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