linux-kernel - [irqchip: irq/irqchip-next] irqchip/qcom-pdc: Fix broken locking

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Message-ID: <164607003952.16921.11921713857633233436.tip-bot2@tip-bot2>
Date:   Mon, 28 Feb 2022 17:40:39 -0000
From:   "irqchip-bot for Marc Zyngier" <tip-bot2@...utronix.de>
To:     linux-kernel@...r.kernel.org
Cc:     Marc Zyngier <maz@...nel.org>, tglx@...utronix.de
Subject: [irqchip: irq/irqchip-next] irqchip/qcom-pdc: Fix broken locking

The following commit has been merged into the irq/irqchip-next branch of irqchip:

Commit-ID:     bd9fce2e5ea12ee82821dbc725fa4f97f9094ba1
Gitweb:        https://git.kernel.org/pub/scm/linux/kernel/git/maz/arm-platforms/bd9fce2e5ea12ee82821dbc725fa4f97f9094ba1
Author:        Marc Zyngier <maz@...nel.org>
AuthorDate:    Thu, 24 Feb 2022 10:12:25 
Committer:     Marc Zyngier <maz@...nel.org>
CommitterDate: Mon, 28 Feb 2022 17:32:26 

irqchip/qcom-pdc: Fix broken locking

pdc_enable_intr() serves as a primitive to qcom_pdc_gic_{en,dis}able,
and has a raw spinlock for mutual exclusion, which is uses with
interruptible primitives.

This means that this critical section can itself be interrupted.
Should the interrupt also be a PDC interrupt, and the endpoint driver
perform an irq_disable() on that interrupt, we end-up in a deadlock.

Fix this by using the irqsave/irqrestore variants of the locking
primitives.

Signed-off-by: Marc Zyngier <maz@...nel.org>
Link: https://lore.kernel.org/r/20220224101226.88373-5-maz@kernel.org
---
 drivers/irqchip/qcom-pdc.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/irqchip/qcom-pdc.c b/drivers/irqchip/qcom-pdc.c
index 837ca69..0cd20dd 100644
--- a/drivers/irqchip/qcom-pdc.c
+++ b/drivers/irqchip/qcom-pdc.c
@@ -55,17 +55,18 @@ static u32 pdc_reg_read(int reg, u32 i)
 static void pdc_enable_intr(struct irq_data *d, bool on)
 {
 	int pin_out = d->hwirq;
+	unsigned long flags;
 	u32 index, mask;
 	u32 enable;
 
 	index = pin_out / 32;
 	mask = pin_out % 32;
 
-	raw_spin_lock(&pdc_lock);
+	raw_spin_lock_irqsave(&pdc_lock, flags);
 	enable = pdc_reg_read(IRQ_ENABLE_BANK, index);
 	enable = on ? ENABLE_INTR(enable, mask) : CLEAR_INTR(enable, mask);
 	pdc_reg_write(IRQ_ENABLE_BANK, index, enable);
-	raw_spin_unlock(&pdc_lock);
+	raw_spin_unlock_irqrestore(&pdc_lock, flags);
 }
 
 static void qcom_pdc_gic_disable(struct irq_data *d)