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From:   <alice.chao@mediatek.com>
To:     Alim Akhtar <alim.akhtar@samsung.com>,
        Avri Altman <avri.altman@wdc.com>,
        Bart Van Assche <bvanassche@acm.org>,
        "James E.J. Bottomley" <jejb@linux.ibm.com>,
        "Martin K. Petersen" <martin.petersen@oracle.com>,
        Matthias Brugger <matthias.bgg@gmail.com>,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@collabora.com>
CC:     <wsd_upstream@mediatek.com>, <stanley.chu@mediatek.com>,
        <peter.wang@mediatek.com>, <powen.kao@mediatek.com>,
        <naomi.chu@mediatek.com>, <cc.chou@mediatek.com>,
        <tun-yu.yu@mediatek.com>, <chun-hung.wu@mediatek.com>,
        <casper.li@mediatek.com>, Alice Chao <alice.chao@mediatek.com>,
        <linux-scsi@vger.kernel.org>, <linux-kernel@vger.kernel.org>,
        <linux-arm-kernel@lists.infradead.org>,
        <linux-mediatek@lists.infradead.org>
Subject: [PATCH 1/1] core: ufs: fix racing issue between force complete and isr
Date:   Tue, 24 Oct 2023 16:43:21 +0800
Message-ID: <20231024084324.12197-1-alice.chao@mediatek.com>
MIME-Version: 1.0
Content-Type: text/plain
Precedence: bulk

From: Alice Chao <alice.chao@mediatek.com>

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 <alice.chao@mediatek.com>
---
 drivers/ufs/core/ufshcd.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/ufs/core/ufshcd.c b/drivers/ufs/core/ufshcd.c
index 8382e8cfa414..ef6bd146a767 100644
--- a/drivers/ufs/core/ufshcd.c
+++ b/drivers/ufs/core/ufshcd.c
@@ -5518,13 +5518,13 @@ 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);
 		}
-- 
2.18.0