Re: [PATCH] ubi: check kthread_should_stop() after the setting of task state
From: Richard Weinberger
Date: Fri Aug 07 2020 - 15:30:07 EST
On Fri, Aug 7, 2020 at 4:18 AM Zhihao Cheng <chengzhihao1@xxxxxxxxxx> wrote:
> That's where we hold different views. I have 3 viewpoints（You can point
> out which one you disagree.）:
> 1. If kthread_stop() happens at line 12, ubi thread is *marked* with
> stop flag, it will stop at kthread_should_stop() as long as it can reach
> the next iteration.
> 2. If task A is on runqueue and its state is TASK_RUNNING, task A will
> be scheduled to execute.
> 3. If kthread_stop() happens at line 12, after program counter going to
> line 14, ubi thead is on runqueue and its state is TASK_RUNNING. I have
> explained this in situation 1 in last session.
> I mean ubi thread is on runqueue with TASK_RUNNING state & stop flag
> after the process you described.
> Line 12 kthread_stop()
> set_bit(mark stop flag) && wake_up_process(enqueue &&
> set TASK_RUNNING ) => TASK_RUNNING & stop flag & on runqueue
> Line 13 schedule()
> Do nothing but pick next task to execute
You are perfectly right! I failed to concentrate on the state changes.
Now all makes sense, also your comment before the if statement.
So I don't know how to make this more clear in the code.
Maybe it's just me being dense and in need for a vacation. ;-)