![]() ![]() Or maybe not.A Detailed Guide on How to Change Screen Timeout on Mac Beyond that, a detailed read of the logs might help identify the source of the problem, leading to a possible solution. The articles already shared here are a good starting point. Depending on what has failed, there may be no possible recovery other than to restart the OS itself, hence the system crash you are observing.Īs for what might be causing these crashes and what you can do to prevent them, I’m going to have to leave that discussion to others. In your case, if the OS is restarting itself in response to a watchdog, this strongly implies that some part of the kernel (maybe a device driver or extension) is supposed to be periodically updating a global watchdog variable or timer and it is failing to do so. If a separate monitoring process sees that their checkpoints don’t update, it assumes that the corresponding processes have failed. Many processes update checkpoint files as they run.If any one doesn’t get updated, then that thread is assumed to have failed. Many threads update their own resepective global variables, which are monitored by a maximum-priority thread.If the variable doesn’t get updated, then some other thread (or group of threads) has been consuming 100% of the CPU and is probably hung in an infinite loop (or some other kind of CPU-hogging failure mode). A minimum-priority thread periodically updating a global variable, which is monitored by a maximum-priority thread.There are many other similar mechanisms that may be used to perform this kind of monitoring. The idea is that if the software fails to reset the timer on schedule, it is assumed that the monitored software has failed and therefore needs to be restarted. If the software does not reset the timer, then when the interrupt occurs, the interrupt handler will trigger an action (alert the user, kill the process, restart the device, etc.).The software that is being monitored will periodically reset the timer’s count back to zero.The system starts a hardware timer scheduled to generate an interrupt at some low frequency (maybe every 10 seconds, or every minute or five minutes).A basic one (often used in embedded systems and OS kernels) is based on a hardware timer: There are many different mechanisms for implementing this. Either because of a deadlock or an infinite loop or some other critical problem. I can’t help with your specific situation, but I can provide a bit of background information, in case it helps.Ī “watchdog timer” is a mechanism used to detect when a process or thread has hanged. However, it doesn’t seem that there is any definitive cure known, so I may just have to live with the issue until I can afford an M1 Mac - but even these may suffer from the same fault if Apple themselves can’t get to the bottom or it. I brought it up here because I see that there are some very knowledgeable contributors to Tidbits Talk and I hoped that there might be one who could say what actually happens inside the OS when the problem occurs - as an ex software developer, I’m always looking for someone who sees things like this as a debugging challenge.Īnyway, since reading yet more stuff, I am interested in the more recent suggestions that the Apple Photos app may be part of the problem, as I use Photos extensively myself. I’ve tried most things, including zapping the PRAM, running Apple diagnostics, using the machine without the additional monitor etc. I do understand that the problem has a long history and that Apple has failed to satisfy those who’ve experienced it, which seems very strange. ![]()
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