linux-kernel - [PATCHv3 1/3] kernel/irq: make irq_{enter,exit}() in handle_domain

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Date:   Thu, 30 Sep 2021 21:17:06 +0800
From:   Pingfan Liu <kernelfans@...il.com>
To:     linux-arm-kernel@...ts.infradead.org
Cc:     Pingfan Liu <kernelfans@...il.com>,
        Mark Rutland <mark.rutland@....com>,
        "Paul E. McKenney" <paulmck@...nel.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>, Marc Zyngier <maz@...nel.org>,
        Joey Gouly <joey.gouly@....com>,
        Sami Tolvanen <samitolvanen@...gle.com>,
        Julien Thierry <julien.thierry@....com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Yuichi Ito <ito-yuichi@...itsu.com>,
        linux-kernel@...r.kernel.org
Subject: [PATCHv3 1/3] kernel/irq: make irq_{enter,exit}() in handle_domain_irq() arch optional

When an IRQ is taken, some accounting needs to be performed to enter and
exit IRQ context around the IRQ handler. Historically arch code would
leave this to the irqchip or core IRQ code, but these days we want this
to happen in exception entry code, and architectures such as arm64 do
this.

Currently handle_domain_irq() performs this entry/exit accounting, and
if used on an architecture where the entry code also does this, the
entry/exit accounting will be performed twice per IRQ. This is
problematic as core RCU code such as rcu_is_cpu_rrupt_from_idle()
depends on this happening once per IRQ, and will not detect quescent
periods correctly, leading to stall warnings.

As irqchip drivers which use handle_domain_irq() need to work on
architectures with or without their own entry/exit accounting, this
patch makes handle_domain_irq() conditionally perform the entry
accounting depending on a new HAVE_ARCH_IRQENTRY Kconfig symbol that
architectures can select if they perform this entry accounting
themselves.

For architectures which do not select the symbol. there should be no
functional change as a result of this patch.

Signed-off-by: Pingfan Liu <kernelfans@...il.com>
Reviewed-by: Mark Rutland <mark.rutland@....com>
Cc: "Paul E. McKenney" <paulmck@...nel.org>
Cc: Catalin Marinas <catalin.marinas@....com>
Cc: Will Deacon <will@...nel.org>
Cc: Marc Zyngier <maz@...nel.org>
Cc: Joey Gouly <joey.gouly@....com>
Cc: Sami Tolvanen <samitolvanen@...gle.com>
Cc: Julien Thierry <julien.thierry@....com>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Yuichi Ito <ito-yuichi@...itsu.com>
Cc: linux-kernel@...r.kernel.org
To: linux-arm-kernel@...ts.infradead.org
---
 kernel/irq/Kconfig   | 3 +++
 kernel/irq/irqdesc.c | 4 ++++
 2 files changed, 7 insertions(+)

diff --git a/kernel/irq/Kconfig b/kernel/irq/Kconfig
index fbc54c2a7f23..defa1db2d664 100644
--- a/kernel/irq/Kconfig
+++ b/kernel/irq/Kconfig
@@ -100,6 +100,9 @@ config IRQ_MSI_IOMMU
 config HANDLE_DOMAIN_IRQ
 	bool

+config HAVE_ARCH_IRQENTRY
+	bool
+
 config IRQ_TIMINGS
 	bool

diff --git a/kernel/irq/irqdesc.c b/kernel/irq/irqdesc.c
index 4e3c29bb603c..fd5dd9d278b5 100644
--- a/kernel/irq/irqdesc.c
+++ b/kernel/irq/irqdesc.c
@@ -693,7 +693,9 @@ int handle_domain_irq(struct irq_domain *domain,
 	struct irq_desc *desc;
 	int ret = 0;

+#ifndef CONFIG_HAVE_ARCH_IRQENTRY
 	irq_enter();
+#endif

 	/* The irqdomain code provides boundary checks */
 	desc = irq_resolve_mapping(domain, hwirq);
@@ -702,7 +704,9 @@ int handle_domain_irq(struct irq_domain *domain,
 	else
 		ret = -EINVAL;

+#ifndef CONFIG_HAVE_ARCH_IRQENTRY
 	irq_exit();
+#endif
 	set_irq_regs(old_regs);
 	return ret;
 }
-- 
2.31.1