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From 446e65ed8fcd174687364fa85491144ad58da584 Mon Sep 17 00:00:00 2001
From: Thomas Gleixner <tglx@linutronix.de>
Date: Tue, 9 Mar 2021 09:55:53 +0100
Subject: [PATCH 149/296] softirq: Add RT specific softirq accounting
Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/5.10/older/patches-5.10.35-rt39.tar.xz
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 6e324d455a0c..1a146988088d 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1039,6 +1039,9 @@ 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
--
2.30.2
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