rcu: Eliminate NOCBs CPU-state Kconfig options
The CONFIG_RCU_NOCB_CPU_ALL, CONFIG_RCU_NOCB_CPU_NONE, and
CONFIG_RCU_NOCB_CPU_ZERO Kconfig options are used only in testing and
are redundant with the rcu_nocbs= boot parameter. This commit therefore
removes these three Kconfig options and adjusts the rcutorture scripts
to use the boot parameter instead.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
diff --git a/Documentation/timers/NO_HZ.txt b/Documentation/timers/NO_HZ.txt
index 6eaf576..2dcaf9a 100644
--- a/Documentation/timers/NO_HZ.txt
+++ b/Documentation/timers/NO_HZ.txt
@@ -194,32 +194,9 @@
Another approach is to offload RCU callback processing to "rcuo" kthreads
using the CONFIG_RCU_NOCB_CPU=y Kconfig option. The specific CPUs to
-offload may be selected via several methods:
-
-1. One of three mutually exclusive Kconfig options specify a
- build-time default for the CPUs to offload:
-
- a. The CONFIG_RCU_NOCB_CPU_NONE=y Kconfig option results in
- no CPUs being offloaded.
-
- b. The CONFIG_RCU_NOCB_CPU_ZERO=y Kconfig option causes
- CPU 0 to be offloaded.
-
- c. The CONFIG_RCU_NOCB_CPU_ALL=y Kconfig option causes all
- CPUs to be offloaded. Note that the callbacks will be
- offloaded to "rcuo" kthreads, and that those kthreads
- will in fact run on some CPU. However, this approach
- gives fine-grained control on exactly which CPUs the
- callbacks run on, along with their scheduling priority
- (including the default of SCHED_OTHER), and it further
- allows this control to be varied dynamically at runtime.
-
-2. The "rcu_nocbs=" kernel boot parameter, which takes a comma-separated
- list of CPUs and CPU ranges, for example, "1,3-5" selects CPUs 1,
- 3, 4, and 5. The specified CPUs will be offloaded in addition to
- any CPUs specified as offloaded by CONFIG_RCU_NOCB_CPU_ZERO=y or
- CONFIG_RCU_NOCB_CPU_ALL=y. This means that the "rcu_nocbs=" boot
- parameter has no effect for kernels built with RCU_NOCB_CPU_ALL=y.
+offload may be selected using The "rcu_nocbs=" kernel boot parameter,
+which takes a comma-separated list of CPUs and CPU ranges, for example,
+"1,3-5" selects CPUs 1, 3, 4, and 5.
The offloaded CPUs will never queue RCU callbacks, and therefore RCU
never prevents offloaded CPUs from entering either dyntick-idle mode