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block/blk-mq: fix RT kernel issues and interrupt context warnings #433

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block/blk-mq: fix RT kernel issues and interrupt context warnings #433

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a686284
block/blk-mq: fix RT kernel regression with queue_lock in hot path
Dec 22, 2025
839fc61
block: Fix WARN_ON in blk_mq_run_hw_queue when called from interrupt …
Dec 22, 2025
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21 changes: 9 additions & 12 deletions block/blk-mq.c
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Original file line number Diff line number Diff line change
Expand Up @@ -171,7 +171,7 @@ bool __blk_freeze_queue_start(struct request_queue *q,
percpu_ref_kill(&q->q_usage_counter);
mutex_unlock(&q->mq_freeze_lock);
if (queue_is_mq(q))
blk_mq_run_hw_queues(q, false);
blk_mq_run_hw_queues(q, true);
} else {
mutex_unlock(&q->mq_freeze_lock);
}
Expand Down Expand Up @@ -2350,22 +2350,19 @@ void blk_mq_run_hw_queue(struct blk_mq_hw_ctx *hctx, bool async)

might_sleep_if(!async && hctx->flags & BLK_MQ_F_BLOCKING);

/*
* First lockless check to avoid unnecessary overhead.
* Memory barrier below synchronizes with blk_mq_unquiesce_queue().
*/
need_run = blk_mq_hw_queue_need_run(hctx);
if (!need_run) {
unsigned long flags;

/*
* Synchronize with blk_mq_unquiesce_queue(), because we check
* if hw queue is quiesced locklessly above, we need the use
* ->queue_lock to make sure we see the up-to-date status to
* not miss rerunning the hw queue.
*/
spin_lock_irqsave(&hctx->queue->queue_lock, flags);
/* Synchronize with blk_mq_unquiesce_queue() */
smp_mb();
need_run = blk_mq_hw_queue_need_run(hctx);
spin_unlock_irqrestore(&hctx->queue->queue_lock, flags);

if (!need_run)
return;
/* Ensure dispatch list/sw queue updates visible before execution */
smp_mb();
}

if (async || !cpumask_test_cpu(raw_smp_processor_id(), hctx->cpumask)) {
Expand Down