On 5/23/23 06:05, Tian Lan wrote:
> From: Tian Lan <tian.lan@xxxxxxxxxxxx>
>
> If multiple CPUs are sharing the same hardware queue, it can
> cause leak in the active queue counter tracking when __blk_mq_tag_busy()
> is executed simultaneously.
>
> Fixes: ee78ec1077d3 ("blk-mq: blk_mq_tag_busy is no need to return a value")
> Signed-off-by: Tian Lan <tian.lan@xxxxxxxxxxxx>
> Reviewed-by: Ming Lei <ming.lei@xxxxxxxxxx>
Reviewed-by: Damien Le Moal <dlemoal@xxxxxxxxxx>
> ---
> block/blk-mq-tag.c | 12 ++++++++----
> 1 file changed, 8 insertions(+), 4 deletions(-)
>
> diff --git a/block/blk-mq-tag.c b/block/blk-mq-tag.c
> index d6af9d431dc6..dfd81cab5788 100644
> --- a/block/blk-mq-tag.c
> +++ b/block/blk-mq-tag.c
> @@ -39,16 +39,20 @@ void __blk_mq_tag_busy(struct blk_mq_hw_ctx *hctx)
> {
> unsigned int users;
>
> + /*
> + * calling test_bit() prior to test_and_set_bit() is intentional,
> + * it avoids dirtying the cacheline if the queue is already active.
> + */
> if (blk_mq_is_shared_tags(hctx->flags)) {
> struct request_queue *q = hctx->queue;
>
> - if (test_bit(QUEUE_FLAG_HCTX_ACTIVE, &q->queue_flags))
> + if (test_bit(QUEUE_FLAG_HCTX_ACTIVE, &q->queue_flags) ||
> + test_and_set_bit(QUEUE_FLAG_HCTX_ACTIVE, &q->queue_flags))
> return;
> - set_bit(QUEUE_FLAG_HCTX_ACTIVE, &q->queue_flags);
> } else {
> - if (test_bit(BLK_MQ_S_TAG_ACTIVE, &hctx->state))
> + if (test_bit(BLK_MQ_S_TAG_ACTIVE, &hctx->state) ||
> + test_and_set_bit(BLK_MQ_S_TAG_ACTIVE, &hctx->state))
> return;
> - set_bit(BLK_MQ_S_TAG_ACTIVE, &hctx->state);
> }
>
> users = atomic_inc_return(&hctx->tags->active_queues);
--
Damien Le Moal
Western Digital Research
