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    SubjectRe: use of PREEMPT_ACTIVE ?
    On Thu, 2004-03-18 at 14:51, 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

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