c - tasklet 和 workqueue 有什么区别

Question

我是一个 Linux 设备驱动新手，想知道 tasklet 和 workqueue 之间的确切区别。我有以下疑问:

1. Which kernel stack do interrupts, tasklet and workqueue use when running in interrupt/process context?
2. At what priority would tasklet and workqueue run and can we modify it's priority?
3. If I implement my own work queue list, can I schedule/prioritize it independently?

Answer 1

小任务:

• 年龄大(我相信大约 2.3)
• 有一个直接、简单的 API
• 专为低延迟而设计
• 无法 sleep (在软 IRQ 上下文中以原子方式运行，并且保证永远不会在给定处理器的多个 CPU 上运行，对于给定的 tasklet)

工作队列:

• 较新(在 2.5 中引入)
• 拥有灵活的 API(支持更多选项/标志)
• 专为更高的延迟而设计
• 可以 sleep

底线是:将 tasklet 用于高优先级、低延迟的原子任务，这些任务仍必须在硬 IRQ 上下文之外执行。

您可以使用 tasklet_hi_enable/tasklet_hi_schedule(而不是它们各自的 no-_hi 版本)控制 tasklet 的某种优先级。来自 this IBM page :

The normal-priority schedule is performed through the TASKLET_SOFTIRQ-level softirq, where high priority is through the HI_SOFTIRQ-level softirq.

...

Tasklets from the high-priority vector are serviced first, followed by those on the normal vector. Note that each CPU maintains its own normal and high-priority softirq vectors.

对于工作队列，在创建工作队列时，您将使用alloc_workqueue(create_workqueue 已弃用)和can pass a flag要求更高的优先级:

WQ_HIGHPRI:

Work items of a highpri wq are queued to the highpri thread-pool of the target gcwq. Highpri thread-pools are served by worker threads with elevated nice level.

Note that normal and highpri thread-pools don't interact with each other. Each maintain its separate pool of workers and implements concurrency management among its workers.

我无法回答您所有的问题，但无论如何我希望这对您有所帮助。