Whenever the kernel checks for rt_task() to avoid delaying real-time
tasks, we want it to also not delay LITMUS^RT tasks.  Hence, most
calls to rt_task() should be matched by an equivalent call to
is_realtime(). This patch fixes a few places where this was missing.
Notably, this affects the impolementation of select(), which uses
timer_slack_ns when setting up timers for non-real-time tasks.

As with SCHED_FIFO/SCHED_RR tasks, artificial latency is not
desired...

If a task is released on a CPU that is idle, then it is pointless to
send an IPI to another CPU just to schedule the newly released task.
This patch changes check_for_preemptions() to prefer the local CPU
first if it is idle.

Allocating contiguous buffers with kmalloc() is subject to severe
maximum size limits. For Feather-Trace to work, we don't actually need
*physically* contiguous memory; virtually contiguous memory is
sufficient. By switching to vmalloc(), the code gets simpler and we
can support much larger buffers.

For convenience, this patch also adds a configuration option for
the desired Feather-Trace buffer size and increases the default
size.

The 'time_slice' parameter has not been relevant in a couple of years.
The 'completed' flag was misused in a few places. This clean-up patch
removes these outdated remnants.

The PFAIR would not properly schedule tasks that were admitted while
being suspended. This patch changes the task_new() handler to set the
"needs to be requeued" flag on suspended tasks, which is required to
ensure that they are processed correctly by the wake_up() handler.

This patch fixes admission of suspended tasks under the P-FP plugin
analogously to commit 3088111567f334cccff1123f9bd97f2ba52af944.

In the task_new() handler, don't process a job arrival event if the
task is actually suspended. This fixes the admission of suspended
tasks.

This commit fixes admission of suspended tasks under the P-FP plugin
analogously to commit 78ae3306ff8b63a4592044aa28c2f2cbc1d36b20.