Kernel panic loop at startup won’t let Mac boot up

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Kernel panic loop at startup won’t let Mac boot up

Hi guys!

I have an issue with my Mac.

Everything was working well, no apparent sign of malfunction, when I performed the regular reboot of my machine.

But this time, the Mac never rebooted, and it has been two days now that every boot up attempt has failed, over and over.

Because I can’t login, or even boot up in Safe Mode (the kernel panic occurs before the loading screen), I can’t post a log file, though I’ve been able to film it using Verbose Mode.

The boot up process goes at regular speeds before stopping at the line

control ID: 0, coreAudioChannel ID: 0, MASTER oldValue 0x60, newValue 0x60

Then nothing happens for a while, and the next interesting line is

panic(cpu2caller 0xffffffBG1b9fea25): userspace watchdog timeout: no successful checkins from com.apple.logd in 120 seconds

service returned not alive with context: unresponsive dispatch queue(s): com.apple.firehose.lo-vl

(Disclaimer: these are lines transcripts from a video, there might be typos)

I don’t know if these lines are enough to begin to understand what’s going on, tell me if you need the full video or some other extracts of the boot up transcript (or if there is a way for me to send it to you without having access to macOS)

I’ve already tried to boot up Target Mode (success), Safe Mode (failed), NVRAM and PRAM reset (success), Apple Hardware Test (success, no issues), Disk Aid’s SOS (success, drive is OK), macOS reinstall (success), but I can’t get access to my session at all, and Safe Mode is no use, making troubleshooting and bug fixing a bit difficult.

Does anyone have any leads to get this Mac back up and running, at least in order to identify what’s wrong and take action about it?

Thanks so much in advance!

Charles

Posted on Sep 4, 2022 2:54 PM

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Answer 1

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HWTech

Level 9

68,648 points

Sep 7, 2022 4:50 PM in response to N3M1C0

Since you don't have access to another Mac, the best troubleshooting step would be to install macOS to an external USB3 SSD, but if you had a spare USB hard drive it will work as well although performance will be slower. This does two things at once. It tells you whether you can boot macOS from an external drive which if successful tells you the issue is most likely with the internal SSD with a bad SSD, or a software, or file system issue on the internal drive. If successful, it also allows you easier access to recover the data from the internal drive. Plus it would be possible to check the health of the internal SSD with DriveDx and posting the complete text report here using the "Additional Text" icon which looks like a piece of paper.

If you are indeed initiating Safe Mode correctly, then software issues are not likely since Safe Mode should prevent third party software from launching automatically. These leaves a file system issue or some hardware issue.

When running Disk Utility First Aid, make sure to run it on the hidden Container. Within Disk Utility you may need to click "View" and select "Show All Devices" so that the hidden Container appears on the left pane of Disk Utility. Even if First Aid says everything is "Ok", click "Show Details" and scroll back through the report to see if any unfixed errors are detected. If any unfixed errors are detected, then the whole physical SSD will need to be erased before installing macOS and restoring from a backup.

As for hardware issues, make sure to disconnect all unnecessary external devices in case one of them is causing a problem. I suggest connecting the display to another port. The only other way to confirm is by performing a clean install of macOS to either the internal or external drive making sure to test the clean install before installing any third party software and before migrating/restoring from a backup.

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Answer 2

HWTech

Level 9

68,648 points

Sep 4, 2022 5:04 PM in response to N3M1C0

What is the exact model of your Mac which is very important information.

When you reinstalled macOS did you reinstall macOS over top of itself or a clean install? If a clean install, was it to the same internal drive or to an external drive?

If you were able to get into Target Disk Mode, then backup your data if necessary. Then perform a clean install of macOS by first erasing the whole physical drive (Intel Mac only) or the hidden Container (M1/M2 or Intel Mac).

You should always have frequent and regular backups of your computer and all external media (including the cloud) which includes important & unique data.

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Answer 3

N3M1C0 Author

Level 1

31 points

Sep 21, 2022 7:59 AM in response to HWTech

Hi again, HWTech,

So I finally have been able to get a second Mac from work and managed to reportedly recover all data.

Internal SSD has been formatted, macOS has been freshly reinstalled and it has been working like a charm since this morning, I'm just sad not to have been able to figure out exactly what was doing all these problems.

The system seems way more responsive and less cluttered after the clean reinstall (Mac system was 9 years old before this clean reinstall), so I'll see how it goes during the next few days :)

I'll also try to run DriveDX but both Disk Aid and Apple Hardware Diagnostics have returned with no errors, so software must have been the issue all along.

Thanks again!

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Answer 4

N3M1C0 Author

Level 1

31 points

Sep 4, 2022 9:44 PM in response to HWTech

Hi HWTech, thank you so much for answering :)

The Mac is a Mac Pro (late 2013).

The reinstall was on top of itself, and accessing Target Mode has just been « seeing the Thunderbolt icon », I don’t currently have the means (a big enough drive or another Mac) to backup then erase, for now I’m looking for a solution that can avoid completely erasing the internal drive, but if it appears there are no other solutions, I will try and get what’s needed.

I used to have a regular Time Machine backup on my Time Capsule, but I think the TC drive started to fail recently, as no backups have been able to complete successfully for a few months, so I don’t think I can rely on this one as it might be too old.

Charles

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Kernel panic loop at startup won’t let Mac boot up

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