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From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Date: Thu, 29 Jan 2015 15:10:08 +0100
Subject: block/mq: don't complete requests via IPI
Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/5.4/older/patches-5.4.3-rt1.tar.xz
The IPI runs in hardirq context and there are sleeping locks. Assume caches are
shared and complete them on the local CPU.
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
block/blk-mq.c | 8 ++++++++
1 file changed, 8 insertions(+)
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -612,8 +612,16 @@ static void __blk_mq_complete_request(st
}
cpu = get_cpu_light();
+ /*
+ * Avoid SMP function calls for completions because they acquire
+ * sleeping spinlocks on RT.
+ */
+#ifdef CONFIG_PREEMPT_RT
+ shared = true;
+#else
if (!test_bit(QUEUE_FLAG_SAME_FORCE, &q->queue_flags))
shared = cpus_share_cache(cpu, ctx->cpu);
+#endif
if (cpu != ctx->cpu && !shared && cpu_online(ctx->cpu)) {
rq->csd.func = __blk_mq_complete_request_remote;
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