xnu内核中有工作队列功能吗？

Question

I need to use workqueue-like feature on Mac OSX (kernel mode driver) and am looking for a way to add work into a queue to be processed by a kernel thread later. Conceptually this is the same thing as workqueue feature available in Linux kernel. Is there something similar on XNU kernel as well?

Answer 1

I don't think there's a direct equivalent as such, although I admit I'm not intimately familiar with the Linux side, so I'll avoid comparing and just tell you about what's available on macOS/xnu.

I/O Kit IOWorkLoops

If you're building an I/O Kit driver, and especially if you're writing a secondary interrupt handler, you'll be using IOWorkLoops . Interrupts are abstracted by IOEventSource objects, which schedule secondary interrupt handlers to run on the driver's IOWorkLoop .

Each IOWorkLoop wraps one kernel thread and also provides a serialisation/locking mechanism for resources shared with that thread. All jobs submitted to a workloop either explicitly through an IOCommandGate or the workloop object directly, or as a result of an IOEventSource event will be serialised. Note that IOCommandGate jobs will run synchronously on the calling thread, not the workloop thread.

As always with macOS/OSX internals, you will want to look at the header file comments and possibly the implementation in the xnu source for details. I personally find IOWorkLoop sa bit clumsy for some tasks, but if you're dealing with PCI devices, etc. you don't really have a choice.

thread_call

A more lightweight background work mechanism is the thread_call API . It's defined in <kern/thread_call.h> and supports running functions on an OS-managed background thread, optionally after a delay or with a specific priority. This is probably closer to what you know from Linux, has a fairly straightforward API, but is not suitable for secondary interrupt handlers.