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diff --git a/tools/testing/selftests/rcutorture/doc/TREE_RCU-kconfig.txt b/tools/testing/selftests/rcutorture/doc/TREE_RCU-kconfig.txt
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+++ b/tools/testing/selftests/rcutorture/doc/TREE_RCU-kconfig.txt
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+This document gives a brief rationale for the TREE_RCU-related test
+cases, a group that includes TREE_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 all but two, covering CONFIG_PROVE_RCU and not.
+CONFIG_PROVE_RCU -- Do all but one under CONFIG_PROVE_LOCKING.
+CONFIG_PROVE_RCU_DELAY -- Do one.
+CONFIG_RCU_BOOST -- one of TREE_PREEMPT_RCU.
+CONFIG_RCU_BOOST_PRIO -- set to 2 for _BOOST testing.
+CONFIG_RCU_CPU_STALL_INFO -- do one with and without _VERBOSE.
+CONFIG_RCU_CPU_STALL_VERBOSE -- do one with and without _INFO.
+CONFIG_RCU_FANOUT -- Cover hierarchy as currently, but overlap with others.
+CONFIG_RCU_FANOUT_EXACT -- Do one.
+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 TREE_PREEMPT_RCU.
+RCU-bh: Do one with PREEMPT and one with !PREEMPT.
+RCU-sched: Do one with PREEMPT but not BOOST.
+
+
+Hierarchy:
+
+TREE01. CONFIG_NR_CPUS=8, CONFIG_RCU_FANOUT=8, CONFIG_RCU_FANOUT_EXACT=n.
+TREE02. CONFIG_NR_CPUS=8, CONFIG_RCU_FANOUT=3, CONFIG_RCU_FANOUT_EXACT=n,
+        CONFIG_RCU_FANOUT_LEAF=3.
+TREE03. CONFIG_NR_CPUS=8, CONFIG_RCU_FANOUT=4, CONFIG_RCU_FANOUT_EXACT=n,
+        CONFIG_RCU_FANOUT_LEAF=4.
+TREE04. CONFIG_NR_CPUS=8, CONFIG_RCU_FANOUT=2, CONFIG_RCU_FANOUT_EXACT=n,
+        CONFIG_RCU_FANOUT_LEAF=2.
+TREE05. CONFIG_NR_CPUS=8, CONFIG_RCU_FANOUT=6, CONFIG_RCU_FANOUT_EXACT=n
+        CONFIG_RCU_FANOUT_LEAF=6.
+TREE06. CONFIG_NR_CPUS=8, CONFIG_RCU_FANOUT=6, CONFIG_RCU_FANOUT_EXACT=y
+        CONFIG_RCU_FANOUT_LEAF=6.
+TREE07. CONFIG_NR_CPUS=16, CONFIG_RCU_FANOUT=2, CONFIG_RCU_FANOUT_EXACT=n,
+        CONFIG_RCU_FANOUT_LEAF=2.
+TREE08. CONFIG_NR_CPUS=16, CONFIG_RCU_FANOUT=3, CONFIG_RCU_FANOUT_EXACT=y,
+        CONFIG_RCU_FANOUT_LEAF=2.
+TREE09. CONFIG_NR_CPUS=1.
+
+
+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 TREE_PREEMPT_RCU.
+
+CONFIG_RCU_TORTURE_TEST
+CONFIG_RCU_TORTURE_TEST_RUNNABLE
+
+        Always used in KVM testing.
+
+CONFIG_RCU_USER_QS
+
+        Redundant with CONFIG_NO_HZ_FULL.
+
+CONFIG_TREE_PREEMPT_RCU
+CONFIG_TREE_RCU
+
+        These are controlled by CONFIG_PREEMPT.