On 2024/6/27 1:13, Bart Van Assche wrote:
On 6/25/24 8:56 PM, Peter Wang (王信友) wrote:
Sorry I have not explain root-cause clearly. I will add more clear root-cause analyze next version.
And it is not an invalid pointer is passed to blk_mq_unique_tag(), I means blk_mq_unique_tag function try access null pointer. It is differnt and cause misunderstanding.
The null pinter blk_mq_unique_tag try access is: rq->mq_hctx(NULL)->queue_num.
The racing flow is:
Thread A ufshcd_err_handler step 1 ufshcd_cmd_inflight(true) step 3 ufshcd_mcq_req_to_hwq blk_mq_unique_tag rq->mq_hctx->queue_num step 5
Thread B ufs_mtk_mcq_intr(cq complete ISR) step 2 scsi_done ... __blk_mq_free_request rq->mq_hctx = NULL; step 4
How about surrounding the blk_mq_unique_tag() call with atomic_inc_not_zero(&req->ref) / atomic_dec(&req->ref)?
Hi Bart,
A small wonder, then should we append __blk_mq_free_request() if req->ref decreased to 0 like following?
if (req_ref_put_and_test(rq)) __blk_mq_free_request(rq);
Thanks,
Bart.