From 41c27bd3ab76fe73487b5cf57483b527671b790d Mon Sep 17 00:00:00 2001
From: Thomas Gleixner <tglx@linutronix.de>
Date: Tue, 9 Mar 2021 09:55:53 +0100
Subject: [PATCH 146/327] softirq: Add RT specific softirq accounting

RT requires the softirq processing and local bottomhalf disabled regions to
be preemptible. Using the normal preempt count based serialization is
therefore not possible because this implicitely disables preemption.

RT kernels use a per CPU local lock to serialize bottomhalfs. As
local_bh_disable() can nest the lock can only be acquired on the outermost
invocation of local_bh_disable() and released when the nest count becomes
zero. Tasks which hold the local lock can be preempted so its required to
keep track of the nest count per task.

Add a RT only counter to task struct and adjust the relevant macros in
preempt.h.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
 include/linux/hardirq.h | 1 +
 include/linux/preempt.h | 6 +++++-
 include/linux/sched.h   | 3 +++
 3 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/include/linux/hardirq.h b/include/linux/hardirq.h
index 0926e9ca4d85..76878b357ffa 100644
--- a/include/linux/hardirq.h
+++ b/include/linux/hardirq.h
@@ -6,6 +6,7 @@
 #include <linux/preempt.h>
 #include <linux/lockdep.h>
 #include <linux/ftrace_irq.h>
+#include <linux/sched.h>
 #include <linux/vtime.h>
 #include <asm/hardirq.h>
 
diff --git a/include/linux/preempt.h b/include/linux/preempt.h
index 69cc8b64aa3a..9881eac0698f 100644
--- a/include/linux/preempt.h
+++ b/include/linux/preempt.h
@@ -79,7 +79,11 @@
 
 #define nmi_count()	(preempt_count() & NMI_MASK)
 #define hardirq_count()	(preempt_count() & HARDIRQ_MASK)
-#define softirq_count()	(preempt_count() & SOFTIRQ_MASK)
+#ifdef CONFIG_PREEMPT_RT
+# define softirq_count()	(current->softirq_disable_cnt & SOFTIRQ_MASK)
+#else
+# define softirq_count()	(preempt_count() & SOFTIRQ_MASK)
+#endif
 #define irq_count()	(nmi_count() | hardirq_count() | softirq_count())
 
 /*
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 44d8214e5c19..b827f5345db2 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1045,6 +1045,9 @@ struct task_struct {
 	int				softirq_context;
 	int				irq_config;
 #endif
+#ifdef CONFIG_PREEMPT_RT
+	int				softirq_disable_cnt;
+#endif
 
 #ifdef CONFIG_LOCKDEP
 # define MAX_LOCK_DEPTH			48UL
-- 
2.49.0

