lkml.org 
[lkml]   [2004]   [Mar]   [18]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: use of PREEMPT_ACTIVE ?
From
Date
On Thu, 2004-03-18 at 14:51, Julien.Soula@lifl.fr wrote:

> the PREEMPT_ACTIVE flag set by preempt_schedule() or during return of
> interrupt / exception / syscall. And it's tested in schedule() to
> avoid some operations like deactivate_task().
>
> Our purpose is to force deactivation of the task. So we planned to set
> task state to TASK_INTERRUPTIBLE value and then to call
> schedule(). However the PREEMPT_ACTIVE flag can prevent it.
>
> So what is the significance of the PREEMPT_ACTIVE flag and the test in
> schedule() ?

It lets a task be preempted when state != TASK_RUNNING. By preventing
the task from being deactivated, it can be rescheduled correctly.
Otherwise, a task that was, say, TASK_INTERRUPTIBLE could be preempted
before it put itself on a wait queue.

Marking the task that is preempted is a simple solution to the race.

If you want to force the deactivation of the task, there is really no
difference. Set it to TASK_INTERRUPTIBLE, do whatever you need to do,
and call schedule().

PREEMPT_ACTIVE is unrelated to what you want to do.

Robert Love


-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2005-03-22 14:01    [W:0.037 / U:0.516 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site