From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Date: Tue, 14 Jul 2015 14:26:34 +0200
Subject: block/mq: do not invoke preempt_disable()
Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/4.19/older/patches-4.19.25-rt16.tar.xz

preempt_disable() and get_cpu() don't play well together with the sleeping
locks it tries to allocate later.
It seems to be enough to replace it with get_cpu_light() and migrate_disable().

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
 block/blk-mq.c |   10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -570,7 +570,7 @@ static void __blk_mq_complete_request(st
 		return;
 	}
 
-	cpu = get_cpu();
+	cpu = get_cpu_light();
 	if (!test_bit(QUEUE_FLAG_SAME_FORCE, &rq->q->queue_flags))
 		shared = cpus_share_cache(cpu, ctx->cpu);
 
@@ -582,7 +582,7 @@ static void __blk_mq_complete_request(st
 	} else {
 		rq->q->softirq_done_fn(rq);
 	}
-	put_cpu();
+	put_cpu_light();
 }
 
 static void hctx_unlock(struct blk_mq_hw_ctx *hctx, int srcu_idx)
@@ -1360,14 +1360,14 @@ static void __blk_mq_delay_run_hw_queue(
 		return;
 
 	if (!async && !(hctx->flags & BLK_MQ_F_BLOCKING)) {
-		int cpu = get_cpu();
+		int cpu = get_cpu_light();
 		if (cpumask_test_cpu(cpu, hctx->cpumask)) {
 			__blk_mq_run_hw_queue(hctx);
-			put_cpu();
+			put_cpu_light();
 			return;
 		}
 
-		put_cpu();
+		put_cpu_light();
 	}
 
 	kblockd_mod_delayed_work_on(blk_mq_hctx_next_cpu(hctx), &hctx->run_work,
