Re: [RFC PATCH 09/18] kthread: Make it easier to correctly sleep in iterant kthreads

[Jiri Kosina]

On Wed, 10 Jun 2015, Steven Rostedt wrote:

> > Right, and I had not considered that, but it turns out the hung_task
> > detector checks p->state == TASK_UNINTERRUPTIBLE, so TASK_IDLE is indeed
> > safe from that.
> 
> Also, I would assume that TASK_IDLE only makes sense for kernel
> threads, I wonder if we should add an assertion in schedule that
> triggers if a task is scheduling with TASK_IDLE and is not a kernel
> thread (has its own mm?)

For the sake of completnes -- testing for !task_struct->mm is not a 
correct test to find out whether given entity is a kernel thread; kernel 
threads are free to temporarily adopt user struct mm via use_mm() (usually 
for handling AIO on behalf of a particular struct mm).

The correct check is to look at PF_KTHREAD flag in task_struct->flags.

-- 
Jiri Kosina
SUSE Labs
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