linux-kernel - [PATCH] irqchip: mips-gic: Use for_each_set

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Date:   Fri, 19 Aug 2016 18:11:19 +0100
From:   Paul Burton <paul.burton@...tec.com>
To:     Thomas Gleixner <tglx@...utronix.de>,
        Jason Cooper <jason@...edaemon.net>,
        Marc Zyngier <marc.zyngier@....com>,
        <linux-kernel@...r.kernel.org>
CC:     <linux-mips@...ux-mips.org>, Paul Burton <paul.burton@...tec.com>
Subject: [PATCH] irqchip: mips-gic: Use for_each_set_bit to iterate over IRQs

The MIPS GIC driver has previously iterated over bits set in a bitmap
representing pending IRQs by calling find_first_bit, clearing that bit
then calling find_first_bit again until all bits are clear. If multiple
interrupts are pending then this is wasteful, as find_first_bit will
have to loop over the whole bitmap from the start. Use the
for_each_set_bit macro which performs exactly what we need here instead.
It will use find_next_bit and thus only scan over the relevant part of
the bitmap, and it makes the intent of the code clearer.

Signed-off-by: Paul Burton <paul.burton@...tec.com>
---
 drivers/irqchip/irq-mips-gic.c | 7 +------
 1 file changed, 1 insertion(+), 6 deletions(-)

diff --git a/drivers/irqchip/irq-mips-gic.c b/drivers/irqchip/irq-mips-gic.c
index d3ef0fc..e9e5022 100644
--- a/drivers/irqchip/irq-mips-gic.c
+++ b/drivers/irqchip/irq-mips-gic.c
@@ -371,18 +371,13 @@ static void gic_handle_shared_int(bool chained)
 	bitmap_and(pending, pending, intrmask, gic_shared_intrs);
 	bitmap_and(pending, pending, pcpu_mask, gic_shared_intrs);
 
-	intr = find_first_bit(pending, gic_shared_intrs);
-	while (intr != gic_shared_intrs) {
+	for_each_set_bit(intr, pending, gic_shared_intrs) {
 		virq = irq_linear_revmap(gic_irq_domain,
 					 GIC_SHARED_TO_HWIRQ(intr));
 		if (chained)
 			generic_handle_irq(virq);
 		else
 			do_IRQ(virq);
-
-		/* go to next pending bit */
-		bitmap_clear(pending, intr, 1);
-		intr = find_first_bit(pending, gic_shared_intrs);
 	}
 }
 
-- 
2.9.3