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From 4d1c22ea8c409fbf6c0c8c4116ccb566ca66b770 Mon Sep 17 00:00:00 2001
From: Thomas Gleixner <tglx@linutronix.de>
Date: Fri, 24 Sep 2021 18:12:45 +0200
Subject: [PATCH 031/158] x86/softirq: Disable softirq stacks on PREEMPT_RT
Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/5.15/older/patches-5.15.10-rt24.tar.xz
PREEMPT_RT preempts softirqs and the current implementation avoids
do_softirq_own_stack() and only uses __do_softirq().
Disable the unused softirqs stacks on PREEMPT_RT to safe some memory and
ensure that do_softirq_own_stack() is not used which is not expected.
[bigeasy: commit description.]
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Link: https://lore.kernel.org/r/20210924161245.2357247-1-bigeasy@linutronix.de
---
arch/x86/include/asm/irq_stack.h | 3 +++
arch/x86/kernel/irq_32.c | 2 ++
2 files changed, 5 insertions(+)
diff --git a/arch/x86/include/asm/irq_stack.h b/arch/x86/include/asm/irq_stack.h
index 8d55bd11848c..f755c217f67b 100644
--- a/arch/x86/include/asm/irq_stack.h
+++ b/arch/x86/include/asm/irq_stack.h
@@ -201,6 +201,7 @@
IRQ_CONSTRAINTS, regs, vector); \
}
+#ifndef CONFIG_PREEMPT_RT
/*
* Macro to invoke __do_softirq on the irq stack. This is only called from
* task context when bottom halves are about to be reenabled and soft
@@ -214,6 +215,8 @@
__this_cpu_write(hardirq_stack_inuse, false); \
}
+#endif
+
#else /* CONFIG_X86_64 */
/* System vector handlers always run on the stack they interrupted. */
#define run_sysvec_on_irqstack_cond(func, regs) \
diff --git a/arch/x86/kernel/irq_32.c b/arch/x86/kernel/irq_32.c
index 044902d5a3c4..e5dd6da78713 100644
--- a/arch/x86/kernel/irq_32.c
+++ b/arch/x86/kernel/irq_32.c
@@ -132,6 +132,7 @@ int irq_init_percpu_irqstack(unsigned int cpu)
return 0;
}
+#ifndef CONFIG_PREEMPT_RT
void do_softirq_own_stack(void)
{
struct irq_stack *irqstk;
@@ -148,6 +149,7 @@ void do_softirq_own_stack(void)
call_on_stack(__do_softirq, isp);
}
+#endif
void __handle_irq(struct irq_desc *desc, struct pt_regs *regs)
{
--
2.33.1
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