Re: [PATCH v3 1/2] ufs: core: fix ufshcd_clear_cmd racing issue

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On 6/28/24 12:00 AM, peter.wang@xxxxxxxxxxxx wrote:
From: Peter Wang <peter.wang@xxxxxxxxxxxx>

When ufshcd_clear_cmd racing with complete ISR,
the completed tag of request's mq_hctx pointer will set NULL by ISR.
And ufshcd_clear_cmd call ufshcd_mcq_req_to_hwq will get NULL pointer KE.
Return success when request is completed by ISR beacuse sq dosen't
need cleanup.

The racing flow is:

Thread A
ufshcd_err_handler					step 1
	ufshcd_try_to_abort_task
		ufshcd_cmd_inflight(true)		step 3
		ufshcd_clear_cmd
			...
			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

Reviewed-by: Bart Van Assche <bvanassche@xxxxxxx>




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