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    SubjectRe: [PATCH] sched_rt: the task in irq context can be migrated during context switching
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    On Thu, 2012-01-05 at 18:55 +0100, Peter Zijlstra wrote:

    > So the problem is quite real, as already said we don't need to worry
    > about the future, but we might want to fix this in previous kernels.
    > What I'm not entirely sure of is the proposed solution, Steven don't we
    > get in trouble by simply bailing out on the push?

    It shouldn't break anything. We shouldn't be pushing tasks that are
    running on a rq anyway. I don't see any harm here. As this scenario can
    only happen if we get an interrupt after letting go of the rq lock and
    before doing the switch_to(). The schedule_tail() calls
    post_schedule_rt() which does the push again, and will push task A at
    that time.

    That said, I'm not sure this patch is enough. I'm worried about a pull
    happening. As task A is running, we could possible possibly pick it on
    another CPU to do a pull.

    Hmm, looking at the code, the pull already does a task_running() test,
    so I guess we should be fine.

    Acked-by: Steven Rostedt <rostedt@goodmis.org>

    -- Steve




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