Question

There are two cases where the scheduler code schedule() is invoked-

1. When a process voluntarily calls schedule()

2. Timer interrupt calls schedule()

In case 2, I think schedule() runs in interrupt context, but what about the first case? Does it run in the context of the process which invoked it?

Also are there any more scenarios which invoke schedule()?

Answer 1

schedule() always runs in process context. In the second case, when it is initiated by a timer interrupt, it is in the return path back from the kernel to the interrupted process where schedule() is called.