This document gives a brief rationale for the TREE_RCU-related test
cases, a group that includes PREEMPT_RCU.


Kconfig Parameters:

CONFIG_DEBUG_LOCK_ALLOC -- Do three, covering CONFIG_PROVE_LOCKING & not.
CONFIG_DEBUG_OBJECTS_RCU_HEAD -- Do one.
CONFIG_HOTPLUG_CPU -- Do half.  (Every second.)
CONFIG_HZ_PERIODIC -- Do one.
CONFIG_NO_HZ_IDLE -- Do those not otherwise specified. (Groups of two.)
CONFIG_NO_HZ_FULL -- Do two, one with CONFIG_NO_HZ_FULL_SYSIDLE.
CONFIG_NO_HZ_FULL_SYSIDLE -- Do one.
CONFIG_PREEMPT -- Do half.  (First three and #8.)
CONFIG_PROVE_LOCKING -- Do several, covering CONFIG_DEBUG_LOCK_ALLOC=y and not.
CONFIG_PROVE_RCU -- Hardwired to CONFIG_PROVE_LOCKING.
CONFIG_PROVE_RCU_REPEATEDLY -- Do one.
CONFIG_RCU_BOOST -- one of PREEMPT_RCU.
CONFIG_RCU_KTHREAD_PRIO -- set to 2 for _BOOST testing.
CONFIG_RCU_FANOUT -- Cover hierarchy, but overlap with others.
CONFIG_RCU_FANOUT_LEAF -- Do one non-default.
CONFIG_RCU_FAST_NO_HZ -- Do one, but not with CONFIG_RCU_NOCB_CPU_ALL.
CONFIG_RCU_NOCB_CPU -- Do three, see below.
CONFIG_RCU_NOCB_CPU_ALL -- Do one.
CONFIG_RCU_NOCB_CPU_NONE -- Do one.
CONFIG_RCU_NOCB_CPU_ZERO -- Do one.
CONFIG_RCU_TRACE -- Do half.
CONFIG_SMP -- Need one !SMP for PREEMPT_RCU.
CONFIG_RCU_EXPERT=n -- Do a few, but these have to be vanilla configurations.
CONFIG_RCU_EQS_DEBUG -- Do at least one for CONFIG_NO_HZ_FULL and not.
CONFIG_RCU_TORTURE_TEST_SLOW_CLEANUP -- Do for all but a couple TREE scenarios.
CONFIG_RCU_TORTURE_TEST_SLOW_INIT -- Do for all but a couple TREE scenarios.
CONFIG_RCU_TORTURE_TEST_SLOW_PREINIT -- Do for all but a couple TREE scenarios.

RCU-bh: Do one with PREEMPT and one with !PREEMPT.
RCU-sched: Do one with PREEMPT but not BOOST.


Boot parameters:

nohz_full - do at least one.
maxcpu -- do at least one.
rcupdate.rcu_self_test_bh -- Do at least one each, offloaded and not.
rcupdate.rcu_self_test_sched -- Do at least one each, offloaded and not.
rcupdate.rcu_self_test -- Do at least one each, offloaded and not.
rcutree.rcu_fanout_exact -- Do at least one.


Kconfig Parameters Ignored:

CONFIG_64BIT

	Used only to check CONFIG_RCU_FANOUT value, inspection suffices.

CONFIG_NO_HZ_FULL_SYSIDLE_SMALL

	Defer until Frederic uses this.

CONFIG_PREEMPT_COUNT
CONFIG_PREEMPT_RCU

	Redundant with CONFIG_PREEMPT, ignore.

CONFIG_RCU_BOOST_DELAY

	Inspection suffices, ignore.

CONFIG_RCU_CPU_STALL_TIMEOUT

	Inspection suffices, ignore.

CONFIG_RCU_STALL_COMMON

	Implied by TREE_RCU and PREEMPT_RCU.

CONFIG_RCU_TORTURE_TEST
CONFIG_RCU_TORTURE_TEST_RUNNABLE

	Always used in KVM testing.

CONFIG_RCU_TORTURE_TEST_SLOW_PREINIT_DELAY
CONFIG_RCU_TORTURE_TEST_SLOW_INIT_DELAY
CONFIG_RCU_TORTURE_TEST_SLOW_CLEANUP_DELAY

	Inspection suffices, ignore.

CONFIG_PREEMPT_RCU
CONFIG_TREE_RCU
CONFIG_TINY_RCU

	These are controlled by CONFIG_PREEMPT and/or CONFIG_SMP.

CONFIG_SPARSE_RCU_POINTER

	Makes sense only for sparse runs, not for kernel builds.

CONFIG_SRCU
CONFIG_TASKS_RCU

	Selected by CONFIG_RCU_TORTURE_TEST, so cannot disable.

CONFIG_RCU_TRACE

	Implied by CONFIG_RCU_TRACE for Tree RCU.


boot parameters ignored: TBD