linux-kernel - [RFC PATCH 2/6] softirq: Make softirq handling entry/exit generally available

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Message-Id: <20230801132441.559222-3-frederic@kernel.org>
Date:   Tue,  1 Aug 2023 15:24:37 +0200
From:   Frederic Weisbecker <frederic@...nel.org>
To:     LKML <linux-kernel@...r.kernel.org>
Cc:     Frederic Weisbecker <frederic@...nel.org>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        "Paul E . McKenney" <paulmck@...nel.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Anna-Maria Behnsen <anna-maria@...utronix.de>,
        Eric Dumazet <edumazet@...gle.com>
Subject: [RFC PATCH 2/6] softirq: Make softirq handling entry/exit generally available

In order to prepare for re-enabling softirqs from vector callbacks that
are known safe, make the code incrementing the preempt count while
servicing softirqs more generally available.

No intended behaviour change.

Signed-off-by: Frederic Weisbecker <frederic@...nel.org>
---
 include/linux/bottom_half.h |  7 +++++++
 kernel/softirq.c            | 22 ++++++++++++++++------
 2 files changed, 23 insertions(+), 6 deletions(-)

diff --git a/include/linux/bottom_half.h b/include/linux/bottom_half.h
index fc53e0ad56d9..2243c7de4917 100644
--- a/include/linux/bottom_half.h
+++ b/include/linux/bottom_half.h
@@ -33,6 +33,13 @@ static inline void local_bh_enable(void)
 	__local_bh_enable_ip(_THIS_IP_, SOFTIRQ_DISABLE_OFFSET);
 }
 
+static inline void local_bh_enter(void)
+{
+	__local_bh_disable_ip(_RET_IP_, SOFTIRQ_OFFSET);
+}
+
+extern void local_bh_exit(void);
+
 #ifdef CONFIG_PREEMPT_RT
 extern bool local_bh_blocked(void);
 #else
diff --git a/kernel/softirq.c b/kernel/softirq.c
index 1a3c3fe341ea..ba998d572ef4 100644
--- a/kernel/softirq.c
+++ b/kernel/softirq.c
@@ -247,21 +247,26 @@ void __local_bh_enable_ip(unsigned long ip, unsigned int cnt)
 }
 EXPORT_SYMBOL(__local_bh_enable_ip);
 
+inline void local_bh_exit(void)
+{
+	__local_bh_enable(SOFTIRQ_OFFSET, true);
+	WARN_ON_ONCE(in_interrupt());
+}
+
 /*
  * Invoked from ksoftirqd_run() outside of the interrupt disabled section
  * to acquire the per CPU local lock for reentrancy protection.
  */
 static inline void ksoftirqd_run_begin(void)
 {
-	__local_bh_disable_ip(_RET_IP_, SOFTIRQ_OFFSET);
+	local_bh_enter();
 	local_irq_disable();
 }
 
 /* Counterpart to ksoftirqd_run_begin() */
 static inline void ksoftirqd_run_end(void)
 {
-	__local_bh_enable(SOFTIRQ_OFFSET, true);
-	WARN_ON_ONCE(in_interrupt());
+	local_bh_exit();
 	local_irq_enable();
 }
 
@@ -389,15 +394,20 @@ void __local_bh_enable_ip(unsigned long ip, unsigned int cnt)
 }
 EXPORT_SYMBOL(__local_bh_enable_ip);
 
+inline void local_bh_exit(void)
+{
+	__local_bh_enable(SOFTIRQ_OFFSET);
+	WARN_ON_ONCE(in_interrupt());
+}
+
 static inline void softirq_handle_begin(void)
 {
-	__local_bh_disable_ip(_RET_IP_, SOFTIRQ_OFFSET);
+	local_bh_enter();
 }
 
 static inline void softirq_handle_end(void)
 {
-	__local_bh_enable(SOFTIRQ_OFFSET);
-	WARN_ON_ONCE(in_interrupt());
+	local_bh_exit();
 }
 
 static inline void ksoftirqd_run_begin(void)
-- 
2.34.1