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    Subject[patch 2/2] sched: Protect sched_rr_get_param access to task->sched_class
    sched_rr_get_param calls task->sched_class->get_rr_interval(task)
    without protection against a concurrent sched_setscheduler() call
    which modifies task->sched_class.

    Serialize the access with task_rq_lock(task);

    Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
    ---
    kernel/sched.c | 4 ++++
    1 file changed, 4 insertions(+)

    Index: linux-2.6-tip/kernel/sched.c
    ===================================================================
    --- linux-2.6-tip.orig/kernel/sched.c
    +++ linux-2.6-tip/kernel/sched.c
    @@ -6887,6 +6887,8 @@ SYSCALL_DEFINE2(sched_rr_get_interval, p
    {
    struct task_struct *p;
    unsigned int time_slice;
    + unsigned long flags;
    + struct rq *rq;
    int retval;
    struct timespec t;

    @@ -6903,7 +6905,9 @@ SYSCALL_DEFINE2(sched_rr_get_interval, p
    if (retval)
    goto out_unlock;

    + rq = task_rq_lock(p, &flags);
    time_slice = p->sched_class->get_rr_interval(p);
    + task_rq_unlock(rq, &flags);

    read_unlock(&tasklist_lock);
    jiffies_to_timespec(time_slice, &t);



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