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2015-10-07Merge branches 'doc.2015.10.06a', 'percpu-rwsem.2015.10.06a' and 'torture.2015.10.06a' into HEADPaul E. McKenney6-4/+20
doc.2015.10.06a: Documentation updates. percpu-rwsem.2015.10.06a: Optimization of per-CPU reader-writer semaphores. torture.2015.10.06a: Torture-test updates.
2015-10-06torture: Forgive non-plural argumentsPaul E. McKenney1-3/+3
This commit allows --bootarg instead of --bootargs, --config instead of --configs, and --qemu-arg instead of --qemu-args. For those cases where a native English speaker might auto-correct the argument to be incorrect. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Reviewed-by: Josh Triplett <josh@joshtriplett.org>
2015-10-06locktorture: Add torture tests for percpu_rwsemPaul E. McKenney3-0/+8
This commit adds percpu_rwsem tests based on the earlier rwsem tests. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Davidlohr Bueso <dave@stgolabs.net> Reviewed-by: Josh Triplett <josh@joshtriplett.org>
2015-10-06locktorture: Support rtmutex torturingDavidlohr Bueso3-1/+9
Real time mutexes is one of the few general primitives that we do not have in locktorture. Address this -- a few considerations: o To spice things up, enable competing thread(s) to become rt, such that we can stress different prio boosting paths in the rtmutex code. Introduce a ->task_boost callback, only used by rtmutex-torturer. Tasks will boost/deboost around every 50k (arbitrarily) lock/unlock operations. o Hold times are similar to what we have for other locks: only occasionally having longer hold times (per ~200k ops). So we roughly do two full rt boost+deboosting ops with short hold times. Signed-off-by: Davidlohr Bueso <dbueso@suse.de> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Reviewed-by: Josh Triplett <josh@joshtriplett.org>
2015-08-04Merge branches 'doc.2015.07.15a' and 'torture.2015.07.15a' into HEADPaul E. McKenney1-2/+2
doc.2015.07.15a: Documentation updates. torture.2015.07.15a: Torture-test updates.
2015-07-17rcu: Remove CONFIG_RCU_CPU_STALL_INFOPaul E. McKenney12-12/+0
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>
2015-07-15rcutorture: Enable lockdep-RCU on TASKS01Paul E. McKenney1-2/+2
Currently none of the RCU-tasks scenarios enables lockdep-RCU, which causes bugs to be missed. This commit therefore enables lockdep-RCU on TASKS01. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2015-05-27Merge branches 'array.2015.05.27a', 'doc.2015.05.27a', 'fixes.2015.05.27a', 'hotplug.2015.05.27a', 'init.2015.05.27a', 'tiny.2015.05.27a' and 'torture.2015.05.27a' into HEADPaul E. McKenney28-56/+72
array.2015.05.27a: Remove all uses of RCU-protected array indexes. doc.2015.05.27a: Docuemntation updates. fixes.2015.05.27a: Miscellaneous fixes. hotplug.2015.05.27a: CPU-hotplug updates. init.2015.05.27a: Initialization/Kconfig updates. tiny.2015.05.27a: Updates to Tiny RCU. torture.2015.05.27a: Torture-testing updates.
2015-05-27rcutorture: Allow repetition factors in Kconfig-fragment listsPaul E. McKenney1-6/+19
Although it is currently possible to run the same test in parallel, '--config "TINY01 TINY01 TINY01"' can get a bit verbose, especially if you want to run 48 instances of TINY01 in parallel. This commit therefore allows prefixing the Kconfig fragment with a repeat count, for example, '--config "48*TINY01"' to run 48 instances in parallel. At least assuming that you have 48 CPUs and also gave '--cpus 48'. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Reviewed-by: Josh Triplett <josh@joshtriplett.org>
2015-05-27rcutorture: Display "make oldconfig" errorsPaul E. McKenney2-1/+5
The current rcutorture scripting fails to dump out errors from "make oldconfig", so this commit addresses this issue. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Reviewed-by: Josh Triplett <josh@joshtriplett.org>
2015-05-27rcutorture: Update TREE_RCU-kconfig.txtPaul E. McKenney8-30/+21
This commit updates TREE_RCU-kconfig.txt to reflect changes in RCU's Kconfig setup. This commit also updates rcutorture's Kconfig fragments to account for Kconfig parameters that are now driven directly off of other Kconfig parameters. The #CHECK# prefix tells the rcutorture scripts to take no action to try to set the Kconfig parameter, but to check that it does in fact get set. This is useful for verifying that Kconfig parameters that are supposed to be automatically set do in fact get set to the required values. Reported-by: Pranith Kumar <bobby.prani@gmail.com> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Reviewed-by: Josh Triplett <josh@joshtriplett.org>
2015-05-27rcutorture: Make rcutorture scripts force RCU_EXPERTPaul E. McKenney13-0/+13
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>
2015-05-27rcutorture: Update configuration fragments for rcutree.rcu_fanout_exactPaul E. McKenney12-9/+3
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>
2015-05-27rcutorture: TASKS_RCU set directly, so don't explicitly set itPaul E. McKenney3-3/+0
The TASKS01, TASKS02, and TASKS03 rcutorture config fragments currently set CONFIG_TASKS_RCU. However, now that the value of this Kconfig parameter is set via "select" statements, it is no longer necessary to set it explicitly. This commit therefore removes it from the Kconfig fragments. 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>
2015-05-27rcutorture: Test SRCU cleanup code pathPaul E. McKenney1-1/+1
The current rcutorture testing does not do any cleanup operations. This works because the srcu_struct is statically allocated, but it does represent a memory leak of the associated dynamically allocated ->per_cpu_ref per-CPU variables. However, rcutorture currently uses a statically allocated srcu_struct, which cannot legally be passed to cleanup_srcu_struct(). Therefore, this commit adds a second form of srcu (called srcud) that dynamically allocates and frees the associated per-CPU variables. This commit also adds a ->cleanup() member to rcu_torture_ops that is invoked at the end of the test, after ->cb_barriers(). This ->cleanup() pointer is NULL for all existing tests, and thus only used for scrud. Finally, the SRCU-P torture-test configuration selects scrud instead of srcu, with SRCU-N continuing to use srcu, thereby testing both static and dynamic srcu_struct structures. Reported-by: "Ahmed, Iftekhar" <ahmedi@onid.oregonstate.edu> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Reviewed-by: Josh Triplett <josh@joshtriplett.org>
2015-05-27rcutorture: Exchange TREE03 and TREE08 NR_CPUS, speed up CPU hotplugPaul E. McKenney3-2/+3
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>
2015-05-27rcutorture: Exchange TREE03 and TREE04 geometriesPaul E. McKenney2-4/+4
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>
2015-05-27rcutorture: Test both RCU-sched and RCU-bh for Tiny RCUPaul E. McKenney1-0/+1
Tiny RCU supports both RCU-sched and RCU-bh, but only RCU-sched is currently tested by the rcutorture scripts. This commit therefore changes the TINY02 configuration to test RCU-bh, with TINY01 continuing to test RCU-sched. This shortcoming of the current rcutorture tests was located by mutation testing by Iftekhar. The idea behind mutation testing is to automatically mutate the code under test. If a given mutant is not caught by testing, this is a hint that the testing might need to be improved, as was the case here. Note that this is only a hint because it is possible to mutate the code into something else that still works. For example, a mutation that removes (say) a WARN_ON() will not normally result in a test failure. This change resulted in the test failure caused by list mishandling, which is fixed by the next commit. Reported-by: "Ahmed, Iftekhar" <ahmedi@onid.oregonstate.edu> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Reviewed-by: Josh Triplett <josh@joshtriplett.org>
2015-05-27rcu: Provide diagnostic option to slow down grace-period scansPaul E. McKenney1-0/+2
Grace-period scans of the rcu_node combining tree normally proceed quite quickly, so that it is very difficult to reproduce races against them. This commit therefore allows grace-period pre-initialization and cleanup to be artificially slowed down, increasing race-reproduction probability. A pair of pairs of new Kconfig parameters are provided, RCU_TORTURE_TEST_SLOW_PREINIT to enable the slowing down of propagating CPU-hotplug changes up the combining tree along with RCU_TORTURE_TEST_SLOW_PREINIT_DELAY to specify the delay in jiffies, and RCU_TORTURE_TEST_SLOW_CLEANUP to enable the slowing down of the end-of-grace-period cleanup scan along with RCU_TORTURE_TEST_SLOW_CLEANUP_DELAY to specify the delay in jiffies. Boot-time parameters named rcutree.gp_preinit_delay and rcutree.gp_cleanup_delay allow these delays to be specified at boot time. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2015-03-20Merge branches 'doc.2015.02.26a', 'earlycb.2015.03.03a', 'fixes.2015.03.03a', 'gpexp.2015.02.26a', 'hotplug.2015.03.20a', 'sysidle.2015.02.26b' and 'tiny.2015.02.26a' into HEADPaul E. McKenney2-1/+2
doc.2015.02.26a: Documentation changes earlycb.2015.03.03a: Permit early-boot RCU callbacks fixes.2015.03.03a: Miscellaneous fixes gpexp.2015.02.26a: In-kernel expediting of normal grace periods hotplug.2015.03.20a: CPU hotplug fixes sysidle.2015.02.26b: NO_HZ_FULL_SYSIDLE fixes tiny.2015.02.26a: TINY_RCU fixes
2015-03-11rcutorture: Enable slow grace-period initializationsPaul E. McKenney1-0/+1
This commit sets CONFIG_RCU_TORTURE_TEST_SLOW_INIT=y, but leaves the default time zero. This can be overridden by passing the "--bootargs rcutree.gp_init_delay=1" argument to kvm.sh. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2015-03-03torture: Avoid script syntax error when insufficient CPUsPaul E. McKenney1-1/+1
Parentheses are special to bash, so use an overflow flag that doesn't use them. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2015-01-15Merge branches 'doc.2015.01.07a', 'fixes.2015.01.15a', 'preempt.2015.01.06a', 'srcu.2015.01.06a', 'stall.2015.01.16a' and 'torture.2015.01.11a' into HEADPaul E. McKenney5-13/+38
doc.2015.01.07a: Documentation updates. fixes.2015.01.15a: Miscellaneous fixes. preempt.2015.01.06a: Changes to handling of lists of preempted tasks. srcu.2015.01.06a: SRCU updates. stall.2015.01.16a: RCU CPU stall-warning updates and fixes. torture.2015.01.11a: RCU torture-test updates and fixes.
2015-01-10torture: Flag console.log file to prevent holdovers from earlier runsPaul E. McKenney1-0/+1
A system misconfiguration that prevents qemu from running at all (for example, a missing dynamically linked library) will keep the console.log file from the previous run. This can fool the developer into thinking that this failed run actually completed correctly. This commit therefore overwrites the console.log file just before launching qemu. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2015-01-10torture: Add "-enable-kvm -soundhw pcspk" to qemu command linePaul E. McKenney1-4/+4
More recent qemu implementations really want "-enable-kvm", and the "-soundhw pcspk" makes the script a bit less dependent on odd audio libraries being installed. This commit therefore adds both to the default qemu command line. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2015-01-10rcutorture: Handle different mpstat versionsPaul E. McKenney1-1/+1
The mpstat command recently added the %gnice column, which messes up the cpu2use.sh script's idle-CPU calculations. This commit therefore uses $NF instead of $12 to select the last (%idle) column. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2015-01-10rcutorture: Make build-output parsing correctly flag RCU's warningsPaul E. McKenney1-7/+13
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2015-01-10rcutorture: Issue warnings on close calls due to Reader Batch blowsPaul E. McKenney1-0/+18
Normal rcutorture checking overestimates grace periods somewhat due to the fact that there is a delay from a grace-period request until the start of the corresponding grace period and another delay from the end of that grace period to notification of the requestor. This means that rcutorture's detection of RCU bugs is less sensitive than it might be. It turns out that rcutorture also checks the underlying grace-period "completed" counter (displayed in Reader Batch output), which in theory allows rcutorture to do exact checks. In practice, memory misordering (by both compiler and CPU) can result in false positives. However, experience on x86 shows that these false positives are quite rare, occurring less than one time per 1,000 hours of testing. This commit therefore does the exact checking, giving a warning if any Reader Batch blows happen, and flagging an error if they happen more often than once every three hours in long tests. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2015-01-06rcutorture: Add checks for stall ending before dump startPaul E. McKenney1-1/+1
The current rcutorture scripting checks for actual stalls (via the "Call Trace:" check), but fails to spot the case where a stall ends just as it is being detected. This commit therefore adds a check for this case. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2014-11-13Merge branches 'torture.2014.11.03a', 'cpu.2014.11.03a', 'doc.2014.11.13a', 'fixes.2014.11.13a', 'signal.2014.10.29a' and 'rt.2014.10.29a' into HEADPaul E. McKenney13-28/+16
cpu.2014.11.03a: Changes for per-CPU variables. doc.2014.11.13a: Documentation updates. fixes.2014.11.13a: Miscellaneous fixes. signal.2014.10.29a: Signal changes. rt.2014.10.29a: Real-time changes. torture.2014.11.03a: torture-test changes.
2014-11-03rcutorture: Remove obsolete kversion param in kvm.shPranith Kumar2-15/+6
Now that we have removed configs based on kernel version, we can also remove the kversion parameter in kvm.sh. Signed-off-by: Pranith Kumar <bobby.prani@gmail.com> Reviewed-by: Josh Triplett <josh@joshtriplett.org> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2014-11-03rcutorture: Remove stale test configurationsPranith Kumar71-1588/+0
Remove rcutorture configuration files which are no longer necessary. Signed-off-by: Pranith Kumar <bobby.prani@gmail.com> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2014-11-03rcutorture: Enable RCU self test in configsPranith Kumar6-0/+12
Add config and boot parameters to enable the self tests in rcutorture testing. Signed-off-by: Pranith Kumar <bobby.prani@gmail.com> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2014-11-03torture: Run Linux-kernel binary out of results directoryPaul E. McKenney1-2/+2
The rcutorture scripts create a qemu-cmd script containing the actual qemu command. However, this command references the build directory, which will be overwritten by later builds. This commit therefore runs the kernel out of the results directory so that less hand-editing is required to re-run a previous test. 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>
2014-10-29rcu: Remove redundant TREE_PREEMPT_RCU config optionPranith Kumar34-38/+38
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>
2014-10-29rcu: Unify boost and kthread prioritiesClark Williams2-3/+3
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>
2014-10-28rcu: Remove CONFIG_RCU_CPU_STALL_VERBOSEPaul E. McKenney12-13/+1
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>
2014-09-30locktorture: Support rwlocksDavidlohr Bueso3-0/+8
Add a "rw_lock" torture test to stress kernel rwlocks and their irq variant. Reader critical regions are 5x longer than writers. As such a similar ratio of lock acquisitions is seen in the statistics. In the case of massive contention, both hold the lock for 1/10 of a second. Signed-off-by: Davidlohr Bueso <dbueso@suse.de> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2014-09-16rcutorture: Rename rcutorture_runnable parameterPaul E. McKenney1-1/+1
This commit changes rcutorture_runnable to torture_runnable, which is consistent with the names of the other parameters and is a bit shorter as well. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2014-09-16locktorture: Add test scenario for rwsem_lockPaul E. McKenney3-0/+8
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2014-09-16locktorture: Add test scenario for mutex_lockPaul E. McKenney3-0/+8
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2014-09-16locktorture: Make torture scripting account for new _runnable namePaul E. McKenney1-1/+1
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2014-09-16Merge branch 'rcu-tasks.2014.09.10a' into HEADPaul E. McKenney7-0/+33
rcu-tasks.2014.09.10a: Add RCU-tasks flavor of RCU.
2014-09-10rcutorture: Add RCU-tasks tests to default rcutorture listPaul E. McKenney1-0/+3
Although the test cases have been added, they must be specified explicitly via the kvm.sh --configs argument in order to run them. This commit therefore adds the RCU-tasks tests to the CFLIST so that they will be run automatically by default. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2014-09-07rcutorture: Add RCU-tasks test casesPaul E. McKenney6-0/+30
This commit adds the TASKS01 and TASKS02 Kconfig fragments, along with the corresponding TASKS01.boot and TASKS02.boot boot-parameter files specifying that rcutorture test RCU-tasks instead of the default flavor. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2014-09-07torture: Check for nul bytes in console outputPaul E. McKenney1-0/+4
When starting a new torture run while an old one is still running, both qemu processes can be outputting to the same console.out file. This can cause quite a bit of confusion, so this commit checks for this situation, which is normally indicated by nul bytes in the console output. Yes, if your new run uses up an exact number of blocks of the file, this check will be ineffective, but the odds are not bad. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Reviewed-by: Pranith Kumar <bobby.prani@gmail.com>
2014-09-07torture: Print PID in hung-kernel diagnostic messagePaul E. McKenney1-1/+1
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Reviewed-by: Pranith Kumar <bobby.prani@gmail.com>
2014-09-07rcutorture: Specify CONFIG_CPUMASK_OFFSTACK=y for TREE07Paul E. McKenney1-0/+1
This commit specifies offstack cpumasks in TREE07 in order to catch references to unallocated cpumask_var_t variables. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Reviewed-by: Pranith Kumar <bobby.prani@gmail.com>
2014-09-07rcutorture: Specify MAXSMP=y for TREE01Paul E. McKenney5-5/+26
Setting CONFIG_MAXSMP=y causes cpumasks to be moved offstack, which introduces the possibility of NULL cpumask_var_t pointers. This commit therefore enables CONFIG_MAXSMP=y in TREE01 to increase test coverage. However, because CONFIG_MAXSMP=y implies 8192 CPUs, we need to use the maxcpus= boot parameter to limit the number of CPUs to something reasonable, which in turn requires updating the scripts to handle this. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Reviewed-by: Pranith Kumar <bobby.prani@gmail.com>
2014-09-07rcutorture: Test partial nohz_full= configurationPaul E. McKenney2-1/+2
The current set of tests covers only cases where either all possible CPUs are nohz_full= CPUs or none of them are. Because there have been some recent bug escapes in cases where only some of the CPUs are nohz_full= CPUs, this commit add a configuration where only half of the CPUs are nohz_full= CPUs. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Reviewed-by: Pranith Kumar <bobby.prani@gmail.com>