Last Week on My Mac: A tendency to panic

As we eagerly await the next Apple Event, and a new round of Apple Silicon Macs, I’ve been mulling over what I like and dislike most about the M1 models. Although my list of dislikes is surprisingly short, there’s one item which I had rather hoped wouldn’t be there: the tendency for their kernel to panic. When Apple designs the chips, integrates them into its own logic boards, owns the firmware, writes the kernel and over 550 kernel extensions, you might have thought that panics would be a thing of the past. But they just keep coming.

Some are completely reproducible, but don’t appear to be going anywhere. Perhaps the simplest to reproduce is that of the missing external boot disk: boot your M1 Mac from an external disk, then shut it down and disconnect that disk before trying to start it up. Not only does the absence of the expected external disk cause a panic, but because this occurs during startup, it just loops back until you force the Mac to shut down.

Others may require a bit more external help. Try connecting a dock to your M1 Mac while it’s asleep, then waking it up. Although you might be lucky and get away with this, it seems that a panic is a common result, as if the Mac woke up next to someone who they didn’t expect to be sharing their bed.

One significant improvement that has come in recent years is that panics no longer spell doom for the file system. HFS+ regularly suffered collateral damage, even after journalling was added. APFS with its copy-on-write does at least make it far less likely that a panic will result in other problems.

When I’ve drawn attention to these problems with M1 Macs in the past, some have chided me for expecting anything better when the hardware is still so relatively novel. Eight months ago, that may have been a reasonable excuse. But here we are with Big Sur 11.4 and these panics are still occurring. Being panics, there’s no room for Apple to claim ignorance of them either: when a Mac restarts after a panic, users are invited to send the panic log to Apple for analysis. Unlike any other problem with macOS, pretty well every kernel panic should be reported in detail.

I don’t know what Apple does with all the panic logs it receives, and suspect that they’re automatically analysed and figures are passed to the engineers concerned. Like other parts of Apple’s Feedback system, communications tend to be exclusively one way, and users never get any response from Apple in return for their report.

Neither does Apple Support seem to know much about kernel panics occurring on M1 Macs. No one has reported to me that Apple Support was able to suggest a successful solution to their kernel panic which occurred on an M1 model. Apple’s staff have, as ever, been very polite and supportive, but seem even more taken aback than I am that any M1 Mac should suffer a panic.

I’m far from convinced that Apple still takes kernel panics as seriously as it did but a year ago. When Catalina 10.15.6 had a serious memory leak in a kernel zone, Apple pushed out a Supplemental Update within a month, even though relatively few users seem to have suffered panics. At one time, Mac OS X made panics more obtrusive to the user, displaying a distinctive multilingual message.

A kernel panic. It is an interesting exercise to get your own screen shot of one.

Now they simply restart, and the panic log suppresses the severity of the event. Other than in that transient window, the user isn’t told that what just happened was a major software failure which penetrated right through to the kernel, and crippled the Mac so badly that restarting was the only option. For any operating system, that’s a very serious fault, something that neither the user nor Apple should tolerate.

The sheer volume of panic logs may be part of the problem and not its solution. If the average Mac panics just once a year, and there are 100 million Macs in regular use, Apple must receive over a quarter of a million panic logs every day, thousands of which will probably be from M1 Macs. Even with sophisticated automated analysis, discovering crucial details in all those can’t be easy.

The shortlist of new features we’d like to see in the next round of Apple Silicon Macs grows longer every day, but close to the top for many users must be that kernel panics become a thing of the past. If Apple can’t achieve that when it controls every last part of the computer, will it ever?