linux-kernel - [PATCH 1/3] genirq: Simplify cond_unmask_eoi

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Date:   Sat, 26 Nov 2022 17:41:32 -0600
From:   Samuel Holland <samuel@...lland.org>
To:     Marc Zyngier <maz@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Palmer Dabbelt <palmer@...belt.com>
Cc:     linux-riscv@...ts.infradead.org,
        Samuel Holland <samuel@...lland.org>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        linux-kernel@...r.kernel.org
Subject: [PATCH 1/3] genirq: Simplify cond_unmask_eoi_irq()

This function calls .irq_eoi in three places, making the logic hard to
follow. Rearrange the function so that .irq_eoi is called only once.

The only time .irq_eoi is not called is when all three if checks fail,
so return early in that case. threads_oneshot can only be nonzero if
IRQS_ONESHOT is set, so the IRQS_ONESHOT check can be omitted there.

The IRQS_ONESHOT condition from the first if statement must then be
copied to the unmask_irq() condition.

Furthermore, if IRQS_ONESHOT is set, mask_irq() must have been called
in the parent function, so the irqd_irq_masked() check is redundant.

Signed-off-by: Samuel Holland <samuel@...lland.org>
---

 kernel/irq/chip.c | 17 +++++++++--------
 1 file changed, 9 insertions(+), 8 deletions(-)

diff --git a/kernel/irq/chip.c b/kernel/irq/chip.c
index 8ac37e8e738a..672bad021a1f 100644
--- a/kernel/irq/chip.c
+++ b/kernel/irq/chip.c
@@ -658,10 +658,15 @@ EXPORT_SYMBOL_GPL(handle_level_irq);
 
 static void cond_unmask_eoi_irq(struct irq_desc *desc, struct irq_chip *chip)
 {
-	if (!(desc->istate & IRQS_ONESHOT)) {
-		chip->irq_eoi(&desc->irq_data);
+	/*
+	 * Do not send an EOI if the thread will do it later in
+	 * unmask_threaded_irq().
+	 */
+	if ((chip->flags & IRQCHIP_EOI_THREADED) && desc->threads_oneshot)
 		return;
-	}
+
+	chip->irq_eoi(&desc->irq_data);
+
 	/*
 	 * We need to unmask in the following cases:
 	 * - Oneshot irq which did not wake the thread (caused by a
@@ -669,12 +674,8 @@ static void cond_unmask_eoi_irq(struct irq_desc *desc, struct irq_chip *chip)
 	 *   completely).
 	 */
 	if (!irqd_irq_disabled(&desc->irq_data) &&
-	    irqd_irq_masked(&desc->irq_data) && !desc->threads_oneshot) {
-		chip->irq_eoi(&desc->irq_data);
+	    (desc->istate & IRQS_ONESHOT) && !desc->threads_oneshot)
 		unmask_irq(desc);
-	} else if (!(chip->flags & IRQCHIP_EOI_THREADED)) {
-		chip->irq_eoi(&desc->irq_data);
-	}
 }
 
 /**
-- 
2.37.4