linux-kernel - [RFC PATCH 50/86] rcu: TASKS_RCU does not need to depend on PREEMPTION

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Message-Id: <20231107215742.363031-51-ankur.a.arora@oracle.com>
Date:   Tue,  7 Nov 2023 13:57:36 -0800
From:   Ankur Arora <ankur.a.arora@...cle.com>
To:     linux-kernel@...r.kernel.org
Cc:     tglx@...utronix.de, peterz@...radead.org,
        torvalds@...ux-foundation.org, paulmck@...nel.org,
        linux-mm@...ck.org, x86@...nel.org, akpm@...ux-foundation.org,
        luto@...nel.org, bp@...en8.de, dave.hansen@...ux.intel.com,
        hpa@...or.com, mingo@...hat.com, juri.lelli@...hat.com,
        vincent.guittot@...aro.org, willy@...radead.org, mgorman@...e.de,
        jon.grimm@....com, bharata@....com, raghavendra.kt@....com,
        boris.ostrovsky@...cle.com, konrad.wilk@...cle.com,
        jgross@...e.com, andrew.cooper3@...rix.com, mingo@...nel.org,
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        David.Laight@...LAB.COM, richard@....at, mjguzik@...il.com,
        Ankur Arora <ankur.a.arora@...cle.com>
Subject: [RFC PATCH 50/86] rcu: TASKS_RCU does not need to depend on PREEMPTION

With PREEMPTION being always enabled, we don't need TASKS_RCU
to be explicitly conditioned on it.

Suggested-by: Paul E. McKenney <paulmck@...nel.org>
Signed-off-by: Ankur Arora <ankur.a.arora@...cle.com>
---
 arch/Kconfig             | 4 ++--
 include/linux/rcupdate.h | 4 ----
 kernel/bpf/Kconfig       | 2 +-
 kernel/trace/Kconfig     | 4 ++--
 4 files changed, 5 insertions(+), 9 deletions(-)

diff --git a/arch/Kconfig b/arch/Kconfig
index 05ce60036ecc..f5179b24072c 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -55,7 +55,7 @@ config KPROBES
 	depends on MODULES
 	depends on HAVE_KPROBES
 	select KALLSYMS
-	select TASKS_RCU if PREEMPTION
+	select TASKS_RCU
 	help
 	  Kprobes allows you to trap at almost any kernel address and
 	  execute a callback function.  register_kprobe() establishes
@@ -104,7 +104,7 @@ config STATIC_CALL_SELFTEST
 config OPTPROBES
 	def_bool y
 	depends on KPROBES && HAVE_OPTPROBES
-	select TASKS_RCU if PREEMPTION
+	select TASKS_RCU
 
 config KPROBES_ON_FTRACE
 	def_bool y
diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
index 5e5f920ade90..7246ee602b0b 100644
--- a/include/linux/rcupdate.h
+++ b/include/linux/rcupdate.h
@@ -171,10 +171,6 @@ static inline void rcu_nocb_flush_deferred_wakeup(void) { }
 	} while (0)
 void call_rcu_tasks(struct rcu_head *head, rcu_callback_t func);
 void synchronize_rcu_tasks(void);
-# else
-# define rcu_tasks_classic_qs(t, preempt) do { } while (0)
-# define call_rcu_tasks call_rcu
-# define synchronize_rcu_tasks synchronize_rcu
 # endif
 
 # ifdef CONFIG_TASKS_TRACE_RCU
diff --git a/kernel/bpf/Kconfig b/kernel/bpf/Kconfig
index 6a906ff93006..e3231b28e2a0 100644
--- a/kernel/bpf/Kconfig
+++ b/kernel/bpf/Kconfig
@@ -27,7 +27,7 @@ config BPF_SYSCALL
 	bool "Enable bpf() system call"
 	select BPF
 	select IRQ_WORK
-	select TASKS_RCU if PREEMPTION
+	select TASKS_RCU
 	select TASKS_TRACE_RCU
 	select BINARY_PRINTF
 	select NET_SOCK_MSG if NET
diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig
index 61c541c36596..e090387b1c2d 100644
--- a/kernel/trace/Kconfig
+++ b/kernel/trace/Kconfig
@@ -163,7 +163,7 @@ config TRACING
 	select BINARY_PRINTF
 	select EVENT_TRACING
 	select TRACE_CLOCK
-	select TASKS_RCU if PREEMPTION
+	select TASKS_RCU
 
 config GENERIC_TRACER
 	bool
@@ -204,7 +204,7 @@ config FUNCTION_TRACER
 	select GENERIC_TRACER
 	select CONTEXT_SWITCH_TRACER
 	select GLOB
-	select TASKS_RCU if PREEMPTION
+	select TASKS_RCU
 	select TASKS_RUDE_RCU
 	help
 	  Enable the kernel to trace every kernel function. This is done
-- 
2.31.1