rcu: provide RCU options on non-preempt architectures too
Impact: build fix
Some old architectures still do not use kernel/Kconfig.preempt, so the
moving of the RCU options there broke their build:
In file included from /home/mingo/tip/include/linux/sem.h:81,
from /home/mingo/tip/include/linux/sched.h:69,
from /home/mingo/tip/arch/alpha/kernel/asm-offsets.c:9:
/home/mingo/tip/include/linux/rcupdate.h:62:2: error: #error "Unknown RCU implementation specified to kernel configuration"
Move these options back to init/Kconfig, which every architecture
includes.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/init/Kconfig b/init/Kconfig
index 9dd7958..6b0fded 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -928,6 +928,80 @@
config PREEMPT_NOTIFIERS
bool
+choice
+ prompt "RCU Implementation"
+ default CLASSIC_RCU
+
+config CLASSIC_RCU
+ bool "Classic RCU"
+ help
+ This option selects the classic RCU implementation that is
+ designed for best read-side performance on non-realtime
+ systems.
+
+ Select this option if you are unsure.
+
+config TREE_RCU
+ bool "Tree-based hierarchical RCU"
+ help
+ This option selects the RCU implementation that is
+ designed for very large SMP system with hundreds or
+ thousands of CPUs.
+
+config PREEMPT_RCU
+ bool "Preemptible RCU"
+ depends on PREEMPT
+ help
+ This option reduces the latency of the kernel by making certain
+ RCU sections preemptible. Normally RCU code is non-preemptible, if
+ this option is selected then read-only RCU sections become
+ preemptible. This helps latency, but may expose bugs due to
+ now-naive assumptions about each RCU read-side critical section
+ remaining on a given CPU through its execution.
+
+endchoice
+
+config RCU_TRACE
+ bool "Enable tracing for RCU"
+ depends on TREE_RCU || PREEMPT_RCU
+ help
+ This option provides tracing in RCU which presents stats
+ in debugfs for debugging RCU implementation.
+
+ Say Y here if you want to enable RCU tracing
+ Say N if you are unsure.
+
+config RCU_FANOUT
+ int "Tree-based hierarchical RCU fanout value"
+ range 2 64 if 64BIT
+ range 2 32 if !64BIT
+ depends on TREE_RCU
+ default 64 if 64BIT
+ default 32 if !64BIT
+ help
+ This option controls the fanout of hierarchical implementations
+ of RCU, allowing RCU to work efficiently on machines with
+ large numbers of CPUs. This value must be at least the cube
+ root of NR_CPUS, which allows NR_CPUS up to 32,768 for 32-bit
+ systems and up to 262,144 for 64-bit systems.
+
+ Select a specific number if testing RCU itself.
+ Take the default if unsure.
+
+config RCU_FANOUT_EXACT
+ bool "Disable tree-based hierarchical RCU auto-balancing"
+ depends on TREE_RCU
+ default n
+ help
+ This option forces use of the exact RCU_FANOUT value specified,
+ regardless of imbalances in the hierarchy. This is useful for
+ testing RCU itself, and might one day be useful on systems with
+ strong NUMA behavior.
+
+ Without RCU_FANOUT_EXACT, the code will balance the hierarchy.
+
+ Say N if unsure.
+
config TREE_RCU_TRACE
def_bool RCU_TRACE && TREE_RCU
select DEBUG_FS