scsi: ufs: core: Fix race between force complete and ISR

While error handler force complete command (Thread A) and completion IRQ
raising (Thread B) of the same command, it may cause race condition.

Below is racing step (from 1 to 6):
	ufshcd_mcq_compl_pending_transfer (Thread A)
1	if (cmd && !test_bit(SCMD_STATE_COMPLETE, &cmd->state)) {
5		spin_lock_irqsave(&hwq->cq_lock, flags);	// wait lock release
		set_host_byte(cmd, DID_REQUEUE);
6		ufshcd_release_scsi_cmd(hba, lrbp);	// access null pointer
		scsi_done(cmd);
		spin_unlock_irqrestore(&hwq->cq_lock, flags);
	}

	ufshcd_mcq_poll_cqe_lock (Thread B)
2	spin_lock_irqsave(&hwq->cq_lock, flags);
	 ufshcd_mcq_poll_cqe_nolock()
	  ufshcd_compl_one_cqe()
3	   ufshcd_release_scsi_cmd()	// lrbp->cmd = NULL;
4	spin_unlock_irqrestore(&hwq->cq_lock, flags);

Signed-off-by: Alice Chao <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Reviewed-by: Bart Van Assche <[email protected]>
Signed-off-by: Martin K. Petersen <[email protected]>

Author: Alice Chao

drivers/ufs/core/ufshcd.c

@@ -5615,13 +5615,13 @@ static void ufshcd_mcq_compl_pending_transfer(struct ufs_hba *hba,
 			 * For those cmds of which the cqes are not present
 			 * in the cq, complete them explicitly.
 			 */
+			spin_lock_irqsave(&hwq->cq_lock, flags);
 			if (cmd && !test_bit(SCMD_STATE_COMPLETE, &cmd->state)) {
-				spin_lock_irqsave(&hwq->cq_lock, flags);
 				set_host_byte(cmd, DID_REQUEUE);
 				ufshcd_release_scsi_cmd(hba, lrbp);
 				scsi_done(cmd);
-				spin_unlock_irqrestore(&hwq->cq_lock, flags);
 			}
+			spin_unlock_irqrestore(&hwq->cq_lock, flags);
 		} else {
 			ufshcd_mcq_poll_cqe_lock(hba, hwq);
 		}