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@kernel.org>
Reviewed-by: Maulik Shah <quic_mkshah@quicinc.com>
Link: https://lore.kernel.org/r/20220224101226.88373-5-maz@kernel.org

diff --git a/drivers/irqchip/qcom-pdc.c b/drivers/irqchip/qcom-pdc.c
index 837ca69..0cd20dd 100644 (file)
--- 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)