[PATCH rcu 02/12] rcu: Make the TASKS_RCU Kconfig option be selected
From: Paul E. McKenney
Date: Mon Apr 18 2022 - 20:13:07 EST
Currently, any kernel built with CONFIG_PREEMPTION=y also gets
CONFIG_TASKS_RCU=y, which is not helpful to people trying to build
preemptible kernels of minimal size.
Because CONFIG_TASKS_RCU=y is needed only in kernels doing tracing of
one form or another, this commit moves from TASKS_RCU deciding when it
should be enabled to the tracing Kconfig options explicitly selecting it.
This allows building preemptible kernels without TASKS_RCU, if desired.
This commit also updates the SRCU-N and TREE09 rcutorture scenarios
in order to avoid Kconfig errors that would otherwise result from
CONFIG_TASKS_RCU being selected without its CONFIG_RCU_EXPERT dependency
being met.
[ paulmck: Apply BPF_SYSCALL feedback from Andrii Nakryiko. ]
Reported-by: Hyeonggon Yoo <42.hyeyoo@xxxxxxxxx>
Tested-by: Hyeonggon Yoo <42.hyeyoo@xxxxxxxxx>
Tested-by: Zhouyi Zhou <zhouzhouyi@xxxxxxxxx>
Cc: Andrii Nakryiko <andrii@xxxxxxxxxx>
Cc: Alexei Starovoitov <ast@xxxxxxxxxx>
Cc: Steven Rostedt <rostedt@xxxxxxxxxxx>
Cc: Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxxxx>
Cc: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxx>
--- Update SRCU-N and TREE09 to avoid Kconfig errors.
Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxx>
---
arch/Kconfig | 1 +
kernel/bpf/Kconfig | 1 +
kernel/rcu/Kconfig | 3 ++-
kernel/trace/Kconfig | 1 +
tools/testing/selftests/rcutorture/configs/rcu/SRCU-N | 2 ++
tools/testing/selftests/rcutorture/configs/rcu/TREE09 | 2 ++
6 files changed, 9 insertions(+), 1 deletion(-)
diff --git a/arch/Kconfig b/arch/Kconfig
index 29b0167c088b..1bf29ce754af 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -35,6 +35,7 @@ config KPROBES
depends on MODULES
depends on HAVE_KPROBES
select KALLSYMS
+ select TASKS_RCU if PREEMPTION
help
Kprobes allows you to trap at almost any kernel address and
execute a callback function. register_kprobe() establishes
diff --git a/kernel/bpf/Kconfig b/kernel/bpf/Kconfig
index d56ee177d5f8..2dfe1079f772 100644
--- a/kernel/bpf/Kconfig
+++ b/kernel/bpf/Kconfig
@@ -27,6 +27,7 @@ config BPF_SYSCALL
bool "Enable bpf() system call"
select BPF
select IRQ_WORK
+ select TASKS_RCU if PREEMPTION
select TASKS_TRACE_RCU
select BINARY_PRINTF
select NET_SOCK_MSG if NET
diff --git a/kernel/rcu/Kconfig b/kernel/rcu/Kconfig
index f559870fbf8b..4f665ae0cf55 100644
--- a/kernel/rcu/Kconfig
+++ b/kernel/rcu/Kconfig
@@ -78,7 +78,8 @@ config TASKS_RCU_GENERIC
task-based RCU implementations. Not for manual selection.
config TASKS_RCU
- def_bool PREEMPTION
+ def_bool 0
+ select IRQ_WORK
help
This option enables a task-based RCU implementation that uses
only voluntary context switch (not preemption!), idle, and
diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig
index 2c43e327a619..bf5da6c4e999 100644
--- a/kernel/trace/Kconfig
+++ b/kernel/trace/Kconfig
@@ -144,6 +144,7 @@ config TRACING
select BINARY_PRINTF
select EVENT_TRACING
select TRACE_CLOCK
+ select TASKS_RCU if PREEMPTION
config GENERIC_TRACER
bool
diff --git a/tools/testing/selftests/rcutorture/configs/rcu/SRCU-N b/tools/testing/selftests/rcutorture/configs/rcu/SRCU-N
index 2da8b49589a0..07f5e0a70ae7 100644
--- a/tools/testing/selftests/rcutorture/configs/rcu/SRCU-N
+++ b/tools/testing/selftests/rcutorture/configs/rcu/SRCU-N
@@ -6,3 +6,5 @@ CONFIG_PREEMPT_NONE=y
CONFIG_PREEMPT_VOLUNTARY=n
CONFIG_PREEMPT=n
#CHECK#CONFIG_RCU_EXPERT=n
+CONFIG_KPROBES=n
+CONFIG_FTRACE=n
diff --git a/tools/testing/selftests/rcutorture/configs/rcu/TREE09 b/tools/testing/selftests/rcutorture/configs/rcu/TREE09
index 8523a7515cbf..fc45645bb5f4 100644
--- a/tools/testing/selftests/rcutorture/configs/rcu/TREE09
+++ b/tools/testing/selftests/rcutorture/configs/rcu/TREE09
@@ -13,3 +13,5 @@ CONFIG_DEBUG_LOCK_ALLOC=n
CONFIG_RCU_BOOST=n
CONFIG_DEBUG_OBJECTS_RCU_HEAD=n
#CHECK#CONFIG_RCU_EXPERT=n
+CONFIG_KPROBES=n
+CONFIG_FTRACE=n
--
2.31.1.189.g2e36527f23