rcu: Remove the RCU_KTHREAD_PRIO Kconfig option

Anything that can be done with the RCU_KTHREAD_PRIO Kconfig option can
also be done with the rcutree.kthread_prio kernel boot parameter.
This commit therefore removes this Kconfig option.

Reported-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Rik van Riel <riel@redhat.com>

rcu: Remove *_SLOW_* Kconfig options

The RCU_TORTURE_TEST_SLOW_PREINIT, RCU_TORTURE_TEST_SLOW_PREINIT_DELAY,
RCU_TORTURE_TEST_SLOW_PREINIT_DELAY, RCU_TORTURE_TEST_SLOW_INIT,
RCU_TORTURE_TEST_SLOW_INIT_DELAY, RCU_TORTURE_TEST_SLOW_CLEANUP,
and RCU_TORTURE_TEST_SLOW_CLEANUP_DELAY Kconfig options are only
useful for torture testing, and there are the rcutree.gp_cleanup_delay,
rcutree.gp_init_delay, and rcutree.gp_preinit_delay kernel boot parameters
that rcutorture can use instead. The effect of these parameters is to
artificially slow down grace period initialization and cleanup in order
to make some types of race conditions happen more often.

This commit therefore simplifies Tree RCU a bit by removing the Kconfig
options and adding the corresponding kernel parameters to rcutorture's
.boot files instead. However, this commit also leaves out the kernel
parameters for TREE02, TREE04, and TREE07 in order to have about the
same number of tests slowed as not slowed. TREE01, TREE03, TREE05,
and TREE06 are slowed, and the rest are not slowed.

Reported-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

torture: Add tests without slow grace period setup/cleanup

This commit moves CONFIG_RCU_TORTURE_TEST_SLOW_CLEANUP,
CONFIG_RCU_TORTURE_TEST_SLOW_INIT, and CONFIG_RCU_TORTURE_TEST_SLOW_PREINIT
from CFcommon to all of the TREE scenarios other than TREE08 and TREE09
in order to do at least some testing without these Kconfig options set.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>

rcu: Remove CONFIG_RCU_CPU_STALL_INFO

The CONFIG_RCU_CPU_STALL_INFO has been default-y for a couple of
releases with no complaints, so it is time to eliminate this Kconfig
option entirely, so that the long-form RCU CPU stall warnings cannot
be disabled. This commit does just that.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

rcutorture: Make rcutorture scripts force RCU_EXPERT

This commit causes the rcutorture scripts to force RCU_EXPERT so that
these scripts can cause rcutorture to torture RCU in the various required
configurations. However, SRCU-P, TASKS03, and TREE09 retain !RCU_EXPERT
in order to ensure testing of the vanilla configuration.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Pranith Kumar <bobby.prani@gmail.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>

rcutorture: Update configuration fragments for rcutree.rcu_fanout_exact

This commit updates rcutortures configuration-fragment files to account
for the move from the CONFIG_RCU_FANOUT_EXACT Kconfig parameter to the
new rcutree.rcu_fanout_exact= boot parameter.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Pranith Kumar <bobby.prani@gmail.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>

rcutorture: Exchange TREE03 and TREE08 NR_CPUS, speed up CPU hotplug

TREE03 has been especially effective at finding bugs lately. This commit
makes it even more effective by speeding up its CPU hotplug testing and
increasing its NR_CPUs from 8 to 16. TREE08's NR_CPUS is decreased from
16 to 8 in order to maintain the same test duration.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>

rcutorture: Exchange TREE03 and TREE04 geometries

Given that the combination of PREEMPT_RCU and HOTPLUG_CPU is producing the
most bugs lately, this commit swaps the TREE03 and TREE04 rcu_node-tree
geometries so that the test exercising PREEMPT_RCU and HOTPLUG_CPU has
three-level rather than two-level rcu_node trees.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>

rcu: Remove redundant TREE_PREEMPT_RCU config option

PREEMPT_RCU and TREE_PREEMPT_RCU serve the same function after
TINY_PREEMPT_RCU has been removed. This patch removes TREE_PREEMPT_RCU
and uses PREEMPT_RCU config option in its place.

Signed-off-by: Pranith Kumar <bobby.prani@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

rcu: Unify boost and kthread priorities

Rename CONFIG_RCU_BOOST_PRIO to CONFIG_RCU_KTHREAD_PRIO and use this
value for both the per-CPU kthreads (rcuc/N) and the rcu boosting
threads (rcub/n).

Also, create the module_parameter rcutree.kthread_prio to be used on
the kernel command line at boot to set a new value (rcutree.kthread_prio=N).

Signed-off-by: Clark Williams <clark.williams@gmail.com>
[ paulmck: Ported to rcu/dev, applied Paul Bolle and Peter Zijlstra feedback. ]
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

rcu: Remove CONFIG_RCU_CPU_STALL_VERBOSE

The CONFIG_RCU_CPU_STALL_VERBOSE Kconfig parameter causes preemptible
RCU's CPU stall warnings to dump out any preempted tasks that are blocking
the current RCU grace period. This information is useful, and the default
has been CONFIG_RCU_CPU_STALL_VERBOSE=y for some years. It is therefore
time for this commit to remove this Kconfig parameter, so that future
kernel builds will always act as if CONFIG_RCU_CPU_STALL_VERBOSE=y.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

rcu: Remove CONFIG_PROVE_RCU_DELAY

The CONFIG_PROVE_RCU_DELAY Kconfig parameter doesn't appear to be very
effective at finding race conditions, so this commit removes it.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Andi Kleen <ak@linux.intel.com>
[ paulmck: Remove definition and uses as noted by Paul Bolle. ]

rcutorture: Introduce "rcu" directory level underneath configs

This commit uses the standard software ploy of introducing another
level of indirection below the configs directory. This allows each
torture-test suite to have its own set of Kconfig files, boot parameters,
and version-specific scripts. Initially, we have only rcu, but lock
will follow soonish.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>