SOCD report detected: (AP watchdog expired)

I was having this issue every couple of days at the end of Feb with my new Mac Mini M1 (1TB, 16GB) with a Time Machine 4GB Seagate HDD (external power) plugged directly into one USB and the other USB going to a powered USB 3.0 Hub.

After reading about this issue on several sites, some suggested that it might be the USB HDD that was the problem. I moved the USB HDD to the powered USB hub instead (left the 2nd USB on the Mini blank). It has been a month using the computer 12+ hours a day and powered on 24/7. The error had not happened since.

this is a logic board issue. watchdog is a component in the processor which resets after a period of time. Usually processor takes care of that. However when the system/processor fails to reset the watchdog, the timer expires and the system reboots which resets the timer. This can happen at anytime. No connection to what you might be doing. I suggest take video when this happens & submit this video at apple store/service centre. They will replace logic board like they did for me. Hope this helps the affected users!!

I have an M1 Mac Mini with two 12TB WD Elements external hard drives attached (via USB-C to USB-A adapters).

The two drives are configured in a RAID 0 array (I care more about throughput and size than reliability).

I have the RAID split up into two APFS volumes, one used by Time Machine and the other for scratch data - both encrypted with FileVault.

I've been suffering random but frequent reboots of the machine while in use or sitting idle. When the machine boots back up it tells me the kernel panicked, sometimes with the AP watchdog expired message that the original poster mentioned.

This persisted from macOS 11.4.x through 11.5.1 which I'm running now.

After many rounds of deleting and recreating the RAID and APFS volumes, the issue kept occurring.

I finally went through this process once more but left encryption disabled, and the problem hasn't happened since!

Do others who are experiencing this have encryption enabled for the filesystems on external drives? I wonder if the bug is specific to M1 Macs with (some specific models of?) USB external drives when FileVault is enabled?

I'm glad my machine isn't randomly rebooting now, but wish I could enable encryption.

Guys, you need to contact Apple and have your computer exchanged. This is not normal. It only happened once to me in 6 months, with lots of peripherals attached and FileVault enabled. Millions of M1 users don't have this problem, so this must be hardware. No need to try tinkering with anything, just have it fixed before the warranty expires

I don't have an external hard drive, but I have an external monitor. When disconnected, the problema goes away.

I think it has to do with external devices being connected when it goes to sleep, or standby.

Possible Solution:

If you have a device that was connected to a USB-Port (also in a Hub). Even if you remove it the AP watchdog still checks that port.

For me the solution was plugging something else into that port and it made the problem vanish.

So if you have 3 USB Ports (1,2,3) in a Thunderbolt Dock and an external HDD was connected to Port 3, after you remove it, the System still checks that port until there is another device connected to that port.

The same might occur for Display-to-USB-C connection or other USB connection so also here if you had USB-C Ports 1,2,3 and connected the cable to port 2, after you change the cable to port 1 the system still checks port 2 and then expires.

Possibly with USB-C Monitors this extends to USB-Ports on the monitor itself and the problem might reoccur if you plug a thumbdrive to any of the USB Ports.

FOLLOW UP - Sent my '21 M1 Pro 14 in. Shipping the box to me took less than 24 hours, and returning it to me also took less than 24 hours.

According to the receipt, they replaced the trackpad completely, and one other component which their description made sound like video RAM (but do not quote me on that).

Since receiving it back, it has been the laptop I always dreamed it would be.

Moral: if possible, send it in for hardware diagnostic, this was not a software issue in my case.

Hello Team,

thanks for the useful discussions and description of the problem symptoms.

Since March I have a MacMini, M1, 16GB, 256GB.

As the internal disk is pretty small I have all my data on an external Cruzial MX500 2TB SSD. The disc is housed in an ICY-BOX USB-C 3.1 enclosure.

Initially everything was running super smooth.....

Then I hit the USB cable probably a bit rough. Since then I have all the problems described in the thread.

Switching cable didn't solve the problem.

Then I suspect that it could have caused some damage in the USB connector at the ICY BOX housing.

Finaly I mounted the Cruzial SSD in another housing connecting via USB 3.0 to the USB-A connector in the MacMINI.

Problems where gone immediately since then.

I haven't been able to verify if using another USB-C 3.1 housing / cable would have solved the problem es well.

Anyhow, for me it works again with new housing and USB-A connection.

So my conclusion is that the connection MacMINI --- USB Cable --- SSD housing is sensitive to any disturbances due to production tolerances and (small) damages.

Those friends suffering with WD drives might want to try to swap the SSD housing if that's an option.

BTW, who in **** has promoted to use this tiny USB-C for connecting serious equipment to serious computers? USB-A is mechanically much more robust.

Just FYI for anyone still following, the AP or Application Processor, is the main CPU of the SoC. The watchdog timer is a very simple component, it just fires an interrupt when the timer goes off, unless the main CPU is alive to keep pinging it regularly.

So basically, the main CPU is locking up completely in these cases, and the timer is noticing this and waking it up long enough to pull a post-mortem kernel panic log and reboot.

Again, I haven't had this problem yet again since I re-imaged my machine completely over DFU with 11.5.1, then subsequently upgraded to 11.5.2 when that came out. The DFU did take way longer than a "supply your own .ipsw previously downloaded from Apple" restore should have, unless it's normally that slow when restoring from a C to A 3.1 gen 2 cable to a 2014 MBP. I can't recommend this method to just anyone, unless they happen to own at least one other Mac they can trust to remain alive for the entire process. If the process is interrupted, it has to be started over again. Thankfully, the DFU part of the firmware is baked into the SoC permanently, so it can't be ruined by a botched restore process.

You'll know if you botched a restore anyway, as the machine will only boot into a "firmware recovery" alert mode. It plays the usual boot chime, but will only sit there blinking its power light in a morse code S-O-S pattern. (3 quick, 3 slow, 3 quick, pause, repeat) The only thing you can do in this mode is power the machine off and initiate DFU mode per the instructions on Apple's documentation, which depends on whether it's a laptop or one of the desktop models.

It may be possible that this is the fix, and that Apple can fix it for customers at their shops, too. Of course, you'll be there for a Long While if it takes the full two hours like it did for me. Maybe it's faster with C to C cables to newer host Macs that have C ports.

A little update on my side.

Since I stopped plugging my 8TB Seagate Usb3 drive and using only a WD SSD UsbC on my M1 Mac mini, I haven’t had any trouble anymore. I am temped to plug it again to see if it’s the reason.

Yes, I've actually resolved the issue on my machine!

I first tried the advice of @d3cbgf a bit back in this thread:

csrutil disable
bputil -nkcas

after which I didn't see the crash for a few days (It's quite likely that this fixed the problem).

However, since I don't want to run my system without this protection (NOT recommended!), I decided to reinstall OS X (On a second volume). Importantly, I didn't enable FileVault on the new volume, and I think this is the "fix" / workaround.

I then tediously reinstalled my applications one by one, to see if any of them caused the crash to start appearing. I'm now running almost everything I did before the reinstall, and I haven't had any system crash for 2 months.

I think the solution was one of the following:

1. Not enabling FileVault on the volume (At this point, I don't want to try enabling it)
2. Not installing any kernel extensions (I had OS X Fuse and perhaps one more kext)

Good luck!

BTW, Please let me know your findings, maybe I can start using FileVault again if that isn't the problem...

There are some things that make this more likely to happen:

• Unpowered USB A hubs
• Plugging USB 3 drives into the USB C port through an adapter
• WD external drives

For example, I don't get this with my Seagate, but I do with my WD drive.

I wonder if monitors affect this? Some have unpowered hubs, which may do this. But what about the ones without hubs?

It seems that some people still get this without any of the above factors.