[PATCH] irq: simplify irq_im_handle_irq()

[Yury Norov]

From: Yury Norov (NVIDIA) <yury.norov@xxxxxxxxx>

Hi Thomas,

The function calls bitmap_empty() for potentially every bit in
work_ctx->pending, which makes a simple bitmap traverse O(N^2).
Fix it by switching to the dedicated for_each_set_bit().

While there, fix using atomic clear_bit() in a context where atomicity
cannot be guaranteed.

Signed-off-by: Yury Norov (NVIDIA) <yury.norov@xxxxxxxxx>
---
 kernel/irq/irq_sim.c | 8 +++-----
 1 file changed, 3 insertions(+), 5 deletions(-)

diff --git a/kernel/irq/irq_sim.c b/kernel/irq/irq_sim.c
index ae4c9cbd1b4b..e05904da7e3d 100644
--- a/kernel/irq/irq_sim.c
+++ b/kernel/irq/irq_sim.c
@@ -128,15 +128,13 @@ static struct irq_chip irq_sim_irqchip = {
 static void irq_sim_handle_irq(struct irq_work *work)
 {
 	struct irq_sim_work_ctx *work_ctx;
-	unsigned int offset = 0;
+	unsigned int offset;
 	int irqnum;
 
 	work_ctx = container_of(work, struct irq_sim_work_ctx, work);
 
-	while (!bitmap_empty(work_ctx->pending, work_ctx->irq_count)) {
-		offset = find_next_bit(work_ctx->pending,
-				       work_ctx->irq_count, offset);
-		clear_bit(offset, work_ctx->pending);
+	for_each_set_bit(offset, work_ctx->pending, work_ctx->irq_count) {
+		__clear_bit(offset, work_ctx->pending);
 		irqnum = irq_find_mapping(work_ctx->domain, offset);
 		handle_simple_irq(irq_to_desc(irqnum));
 	}
-- 
2.43.0