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Date: Thu, 16 Sep 2021 22:13:54 +0800
From: QiuLaibin <qiulaibin@...wei.com>
To: <axboe@...nel.dk>, <linux-kernel@...r.kernel.org>,
<linux-block@...r.kernel.org>
CC: <martin.petersen@...cle.com>, <ming.lei@...hat.com>,
<hare@...e.de>, <asml.silence@...il.com>, <bvanassche@....org>
Subject: [PATCH -next] blk-mq: fix tag_get wait task can't be awakened
ping...
On 2021/9/16 22:10, qiulaibin wrote:
> When multiple hctx share one tagset. The wake_batch is calculated during initialization by queue_depth. But when multiple hctx share one tagset. The queue depth assigned to each user may be smaller than wakup_batch. This may cause the waiting queue to fail to wakup and leads to Hang.
>
> Fix this by recalculating wake_batch when inc or dec active_queues.
>
> Fixes: 0d2602ca30e41 ("blk-mq: improve support for shared tags maps")
> Signed-off-by: Laibin Qiu <qiulaibin@...wei.com>
> ---
> block/blk-mq-tag.c | 44 +++++++++++++++++++++++++++++++++++++++--
> include/linux/sbitmap.h | 8 ++++++++
> lib/sbitmap.c | 3 ++-
> 3 files changed, 52 insertions(+), 3 deletions(-)
>
> diff --git a/block/blk-mq-tag.c b/block/blk-mq-tag.c index 86f87346232a..d02f5ac0004c 100644
> --- a/block/blk-mq-tag.c
> +++ b/block/blk-mq-tag.c
> @@ -16,6 +16,27 @@
> #include "blk-mq-sched.h"
> #include "blk-mq-tag.h"
>
> +static void bt_update_wake_batch(struct sbitmap_queue *bt, unsigned int
> +users) {
> + unsigned int depth;
> +
> + depth = max((bt->sb.depth + users - 1) / users, 4U);
> + sbitmap_queue_update_wake_batch(bt, depth); }
> +
> +/*
> + * Recalculate wakeup batch when tag is shared by hctx.
> + */
> +static void blk_mq_update_wake_batch(struct sbitmap_queue *bitmap_tags,
> + struct sbitmap_queue *breserved_tags, unsigned int users) {
> + if (!users)
> + return;
> +
> + bt_update_wake_batch(bitmap_tags, users);
> + bt_update_wake_batch(breserved_tags, users); }
> +
> /*
> * If a previously inactive queue goes active, bump the active user count.
> * We need to do this before try to allocate driver tag, then even if fail @@ -24,17 +45,29 @@
> */
> bool __blk_mq_tag_busy(struct blk_mq_hw_ctx *hctx) {
> + unsigned int users;
> +
> if (blk_mq_is_sbitmap_shared(hctx->flags)) {
> struct request_queue *q = hctx->queue;
> struct blk_mq_tag_set *set = q->tag_set;
>
> if (!test_bit(QUEUE_FLAG_HCTX_ACTIVE, &q->queue_flags) &&
> - !test_and_set_bit(QUEUE_FLAG_HCTX_ACTIVE, &q->queue_flags))
> + !test_and_set_bit(QUEUE_FLAG_HCTX_ACTIVE, &q->queue_flags)) {
> atomic_inc(&set->active_queues_shared_sbitmap);
> +
> + users = atomic_read(&set->active_queues_shared_sbitmap);
> + blk_mq_update_wake_batch(&set->__bitmap_tags,
> + &set->__breserved_tags, users);
> + }
> } else {
> if (!test_bit(BLK_MQ_S_TAG_ACTIVE, &hctx->state) &&
> - !test_and_set_bit(BLK_MQ_S_TAG_ACTIVE, &hctx->state))
> + !test_and_set_bit(BLK_MQ_S_TAG_ACTIVE, &hctx->state)) {
> atomic_inc(&hctx->tags->active_queues);
> +
> + users = atomic_read(&hctx->tags->active_queues);
> + blk_mq_update_wake_batch(&hctx->tags->__bitmap_tags,
> + &hctx->tags->__breserved_tags, users);
> + }
> }
>
> return true;
> @@ -59,16 +92,23 @@ void __blk_mq_tag_idle(struct blk_mq_hw_ctx *hctx)
> struct blk_mq_tags *tags = hctx->tags;
> struct request_queue *q = hctx->queue;
> struct blk_mq_tag_set *set = q->tag_set;
> + unsigned int users;
>
> if (blk_mq_is_sbitmap_shared(hctx->flags)) {
> if (!test_and_clear_bit(QUEUE_FLAG_HCTX_ACTIVE,
> &q->queue_flags))
> return;
> atomic_dec(&set->active_queues_shared_sbitmap);
> + users = atomic_read(&set->active_queues_shared_sbitmap);
> + blk_mq_update_wake_batch(&set->__bitmap_tags,
> + &set->__breserved_tags, users);
> } else {
> if (!test_and_clear_bit(BLK_MQ_S_TAG_ACTIVE, &hctx->state))
> return;
> atomic_dec(&tags->active_queues);
> + users = atomic_read(&tags->active_queues);
> + blk_mq_update_wake_batch(&tags->__bitmap_tags,
> + &tags->__breserved_tags, users);
> }
>
> blk_mq_tag_wakeup_all(tags, false);
> diff --git a/include/linux/sbitmap.h b/include/linux/sbitmap.h index 2713e689ad66..d49e4f054bfe 100644
> --- a/include/linux/sbitmap.h
> +++ b/include/linux/sbitmap.h
> @@ -406,6 +406,14 @@ static inline void sbitmap_queue_free(struct sbitmap_queue *sbq)
> sbitmap_free(&sbq->sb);
> }
>
> +/**
> + * sbitmap_queue_update_wake_batch() - Recalucate wake batch.
> + * @sbq: Bitmap queue.
> + * @depth: New number of queue depth.
> + */
> +void sbitmap_queue_update_wake_batch(struct sbitmap_queue *sbq,
> + unsigned int depth);
> +
> /**
> * sbitmap_queue_resize() - Resize a &struct sbitmap_queue.
> * @sbq: Bitmap queue to resize.
> diff --git a/lib/sbitmap.c b/lib/sbitmap.c index b25db9be938a..bbe1d663763f 100644
> --- a/lib/sbitmap.c
> +++ b/lib/sbitmap.c
> @@ -457,7 +457,7 @@ int sbitmap_queue_init_node(struct sbitmap_queue *sbq, unsigned int depth, } EXPORT_SYMBOL_GPL(sbitmap_queue_init_node);
>
> -static void sbitmap_queue_update_wake_batch(struct sbitmap_queue *sbq,
> +void sbitmap_queue_update_wake_batch(struct sbitmap_queue *sbq,
> unsigned int depth)
> {
> unsigned int wake_batch = sbq_calc_wake_batch(sbq, depth); @@ -475,6 +475,7 @@ static void sbitmap_queue_update_wake_batch(struct sbitmap_queue *sbq,
> atomic_set(&sbq->ws[i].wait_cnt, 1);
> }
> }
> +EXPORT_SYMBOL_GPL(sbitmap_queue_update_wake_batch);
>
> void sbitmap_queue_resize(struct sbitmap_queue *sbq, unsigned int depth) {
> --
> 2.22.0
>
> .
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