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-rw-r--r--init/Kconfig46
-rw-r--r--init/main.c2
2 files changed, 16 insertions, 32 deletions
diff --git a/init/Kconfig b/init/Kconfig
index 3f7e60995c80..8e8b76d8a272 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -316,38 +316,28 @@ choice
prompt "RCU Implementation"
default TREE_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.
+ thousands of CPUs. It also scales down nicely to
+ smaller systems.
-config PREEMPT_RCU
- bool "Preemptible RCU"
+config TREE_PREEMPT_RCU
+ bool "Preemptable tree-based hierarchical 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.
+ This option selects the RCU implementation that is
+ designed for very large SMP systems with hundreds or
+ thousands of CPUs, but for which real-time response
+ is also required.
endchoice
config RCU_TRACE
bool "Enable tracing for RCU"
- depends on TREE_RCU || PREEMPT_RCU
+ depends on TREE_RCU || TREE_PREEMPT_RCU
help
This option provides tracing in RCU which presents stats
in debugfs for debugging RCU implementation.
@@ -359,7 +349,7 @@ config RCU_FANOUT
int "Tree-based hierarchical RCU fanout value"
range 2 64 if 64BIT
range 2 32 if !64BIT
- depends on TREE_RCU
+ depends on TREE_RCU || TREE_PREEMPT_RCU
default 64 if 64BIT
default 32 if !64BIT
help
@@ -374,7 +364,7 @@ config RCU_FANOUT
config RCU_FANOUT_EXACT
bool "Disable tree-based hierarchical RCU auto-balancing"
- depends on TREE_RCU
+ depends on TREE_RCU || TREE_PREEMPT_RCU
default n
help
This option forces use of the exact RCU_FANOUT value specified,
@@ -387,18 +377,12 @@ config RCU_FANOUT_EXACT
Say N if unsure.
config TREE_RCU_TRACE
- def_bool RCU_TRACE && TREE_RCU
- select DEBUG_FS
- help
- This option provides tracing for the TREE_RCU implementation,
- permitting Makefile to trivially select kernel/rcutree_trace.c.
-
-config PREEMPT_RCU_TRACE
- def_bool RCU_TRACE && PREEMPT_RCU
+ def_bool RCU_TRACE && ( TREE_RCU || TREE_PREEMPT_RCU )
select DEBUG_FS
help
- This option provides tracing for the PREEMPT_RCU implementation,
- permitting Makefile to trivially select kernel/rcupreempt_trace.c.
+ This option provides tracing for the TREE_RCU and
+ TREE_PREEMPT_RCU implementations, permitting Makefile to
+ trivially select kernel/rcutree_trace.c.
endmenu # "RCU Subsystem"
diff --git a/init/main.c b/init/main.c
index 0ec75ce771ac..b34fd8e5edef 100644
--- a/init/main.c
+++ b/init/main.c
@@ -451,6 +451,7 @@ static noinline void __init_refok rest_init(void)
{
int pid;
+ rcu_scheduler_starting();
kernel_thread(kernel_init, NULL, CLONE_FS | CLONE_SIGHAND);
numa_default_policy();
pid = kernel_thread(kthreadd, NULL, CLONE_FS | CLONE_FILES);
@@ -462,7 +463,6 @@ static noinline void __init_refok rest_init(void)
* at least once to get things moving:
*/
init_idle_bootup_task(current);
- rcu_scheduler_starting();
preempt_enable_no_resched();
schedule();
preempt_disable();