Re: [PATCH 1/3] sched: add sched_task_call()

[Jiri Kosina]

On Thu, 19 Feb 2015, Josh Poimboeuf wrote:

> How about with a TIF_IN_USERSPACE thread flag?  It could be cleared/set
> right at the border.  Then for running tasks it's as simple as:
> 
> if (test_tsk_thread_flag(task, TIF_IN_USERSPACE))
> 	klp_switch_task_universe(task);

That's in principle what CONTEXT_TRACKING is doing, i.e. the condition 
we'd be interested in would be

	__this_cpu_read(context_tracking.state) == IN_USER

But it has overhead.

-- 
Jiri Kosina
SUSE Labs
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