linux-kernel - [PATCH v13 02/13] irqchip/sifive-plic: Improve locking safety by using irqsave/irqrestore

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Message-Id: <20240220060718.823229-3-apatel@ventanamicro.com>
Date: Tue, 20 Feb 2024 11:37:07 +0530
From: Anup Patel <apatel@...tanamicro.com>
To: Palmer Dabbelt <palmer@...belt.com>,
	Paul Walmsley <paul.walmsley@...ive.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Rob Herring <robh+dt@...nel.org>,
	Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
	Frank Rowand <frowand.list@...il.com>,
	Conor Dooley <conor+dt@...nel.org>
Cc: Marc Zyngier <maz@...nel.org>,
	Björn Töpel <bjorn@...nel.org>,
	Atish Patra <atishp@...shpatra.org>,
	Andrew Jones <ajones@...tanamicro.com>,
	Sunil V L <sunilvl@...tanamicro.com>,
	Saravana Kannan <saravanak@...gle.com>,
	Anup Patel <anup@...infault.org>,
	linux-riscv@...ts.infradead.org,
	linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org,
	devicetree@...r.kernel.org,
	Anup Patel <apatel@...tanamicro.com>
Subject: [PATCH v13 02/13] irqchip/sifive-plic: Improve locking safety by using irqsave/irqrestore

Now that PLIC driver is probed as a regular platform driver, the lock
dependency validator complains about the safety of handler->enable_lock
usage:

[    0.956775]  Possible interrupt unsafe locking scenario:

[    0.956998]        CPU0                    CPU1
[    0.957247]        ----                    ----
[    0.957439]   lock(&handler->enable_lock);
[    0.957607]                                local_irq_disable();
[    0.957793]                                lock(&irq_desc_lock_class);
[    0.958021]                                lock(&handler->enable_lock);
[    0.958246]   <Interrupt>
[    0.958342]     lock(&irq_desc_lock_class);
[    0.958501]
                *** DEADLOCK ***

To address above, let's use raw_spin_lock_irqsave/unlock_irqrestore()
instead of raw_spin_lock/unlock().

Signed-off-by: Anup Patel <apatel@...tanamicro.com>
---
 drivers/irqchip/irq-sifive-plic.c | 16 ++++++++++------
 1 file changed, 10 insertions(+), 6 deletions(-)

diff --git a/drivers/irqchip/irq-sifive-plic.c b/drivers/irqchip/irq-sifive-plic.c
index 48483a1a41dd..e91077ff171f 100644
--- a/drivers/irqchip/irq-sifive-plic.c
+++ b/drivers/irqchip/irq-sifive-plic.c
@@ -103,9 +103,11 @@ static void __plic_toggle(void __iomem *enable_base, int hwirq, int enable)
 
 static void plic_toggle(struct plic_handler *handler, int hwirq, int enable)
 {
-	raw_spin_lock(&handler->enable_lock);
+	unsigned long flags;
+
+	raw_spin_lock_irqsave(&handler->enable_lock, flags);
 	__plic_toggle(handler->enable_base, hwirq, enable);
-	raw_spin_unlock(&handler->enable_lock);
+	raw_spin_unlock_irqrestore(&handler->enable_lock, flags);
 }
 
 static inline void plic_irq_toggle(const struct cpumask *mask,
@@ -236,6 +238,7 @@ static int plic_irq_set_type(struct irq_data *d, unsigned int type)
 static int plic_irq_suspend(void)
 {
 	unsigned int i, cpu;
+	unsigned long flags;
 	u32 __iomem *reg;
 	struct plic_priv *priv;
 
@@ -253,12 +256,12 @@ static int plic_irq_suspend(void)
 		if (!handler->present)
 			continue;
 
-		raw_spin_lock(&handler->enable_lock);
+		raw_spin_lock_irqsave(&handler->enable_lock, flags);
 		for (i = 0; i < DIV_ROUND_UP(priv->nr_irqs, 32); i++) {
 			reg = handler->enable_base + i * sizeof(u32);
 			handler->enable_save[i] = readl(reg);
 		}
-		raw_spin_unlock(&handler->enable_lock);
+		raw_spin_unlock_irqrestore(&handler->enable_lock, flags);
 	}
 
 	return 0;
@@ -267,6 +270,7 @@ static int plic_irq_suspend(void)
 static void plic_irq_resume(void)
 {
 	unsigned int i, index, cpu;
+	unsigned long flags;
 	u32 __iomem *reg;
 	struct plic_priv *priv;
 
@@ -284,12 +288,12 @@ static void plic_irq_resume(void)
 		if (!handler->present)
 			continue;
 
-		raw_spin_lock(&handler->enable_lock);
+		raw_spin_lock_irqsave(&handler->enable_lock, flags);
 		for (i = 0; i < DIV_ROUND_UP(priv->nr_irqs, 32); i++) {
 			reg = handler->enable_base + i * sizeof(u32);
 			writel(handler->enable_save[i], reg);
 		}
-		raw_spin_unlock(&handler->enable_lock);
+		raw_spin_unlock_irqrestore(&handler->enable_lock, flags);
 	}
 }
 
-- 
2.34.1