rcutorture: Adjust scenarios' Kconfig options for CONFIG_PREEMPT_DYNAMIC

Now that CONFIG_PREEMPT_DYNAMIC=y is the default, kernels that are
ostensibly built with CONFIG_PREEMPT_NONE=y or CONFIG_PREEMPT_VOLUNTARY=y
are now actually built with CONFIG_PREEMPT=y, but are by default booted
so as to disable preemption. Although this allows much more flexibility
from a single kernel binary, it means that the current rcutorture
scenarios won't find build errors that happen only when preemption is
fully disabled at build time.

This commit therefore adds CONFIG_PREEMPT_DYNAMIC=n to several scenarios,
and while in the area switches one from CONFIG_PREEMPT_NONE=y to
CONFIG_PREEMPT_VOLUNTARY=y to add coverage of this Kconfig option.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

rcutorture: Allow rcutorture without RCU Tasks Trace

Unless a kernel builds rcutorture, whether built-in or as a module, that
kernel is also built with CONFIG_TASKS_TRACE_RCU, whether anything else
needs Tasks Trace RCU or not. This unnecessarily increases kernel size.
This commit therefore decouples the presence of rcutorture from the
presence of RCU Tasks Trace.

However, there is a need to select CONFIG_TASKS_TRACE_RCU for
testing purposes. Except that casual users must not be bothered with
questions -- for them, this needs to be fully automated. There is thus
a CONFIG_FORCE_TASKS_TRACE_RCU that selects CONFIG_TASKS_TRACE_RCU,
is user-selectable, but which depends on CONFIG_RCU_EXPERT.

[ paulmck: Apply kernel test robot feedback. ]

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

rcutorture: Provide non-power-of-two Tasks RCU scenarios

This commit adjusts RUDE01 to 3 CPUs and TRACE01 to 5 CPUs in order to
test Tasks RCU's ability to handle non-power-of-two numbers of CPUs.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

rcutorture: Make preemptible TRACE02 enable lockdep

Currently, the CONFIG_PREEMPT_NONE=y rcutorture TRACE01 rcutorture
scenario enables lockdep. This limits its ability to find bugs due to
non-preemptible sections of code being RCU readers, and pretty much all
code thus appearing to lockdep to be an RCU reader. This commit therefore
moves lockdep testing to the CONFIG_PREEMPT=y rcutorture TRACE02 scenario.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

rcutorture: Add TRACE02 scenario enabling RCU Tasks Trace IPIs

This commit adds a TRACE02 scenario which enables preemption and RCU
Tasks Trace IPIs, more specifically, disabling heavyweight readers.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

rcutorture: Add torture tests for RCU Tasks Trace

This commit adds the definitions required to torture the tracing flavor
of RCU tasks.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>