From:   Bean Huo <huobean@gmail.com>
To:     alim.akhtar@samsung.com, avri.altman@wdc.com,
        asutoshd@codeaurora.org, jejb@linux.ibm.com,
        martin.petersen@oracle.com, stanley.chu@mediatek.com,
        beanhuo@micron.com, bvanassche@acm.org, tomas.winkler@intel.com,
        cang@codeaurora.org, daejun7.park@samsung.com
Cc:     linux-scsi@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: [PATCH v1] scsi: ufs: Fix deadlock issue in ufshcd_wait_for_doorbell_clr()
Date:   Tue, 14 Dec 2021 00:00:45 +0100
Message-Id: <20211213230045.492994-1-huobean@gmail.com>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Precedence: bulk

From: Bean Huo <beanhuo@micron.com>

Call shost_for_each_device() with host->host_lock is held will cause
a deadlock situation, which will cause the system to stall (the log
as follow). Fix this issue by narrowing the scope of the lock.

stalls on CPUs/tasks:
all trace:
__switch_to+0x120/0x170
0xffff800011643998
ask dump for CPU 5:
ask:kworker/u16:2   state:R  running task     stack:    0 pid:   80 ppid:     2 flags:0x0000000a
orkqueue: events_unbound async_run_entry_fn
all trace:
__switch_to+0x120/0x170
0x0
ask dump for CPU 6:
ask:kworker/u16:6   state:R  running task     stack:    0 pid:  164 ppid:     2 flags:0x0000000a
orkqueue: events_unbound async_run_entry_fn
all trace:
__switch_to+0x120/0x170
0xffff54e7c4429f80
ask dump for CPU 7:
ask:kworker/u16:4   state:R  running task     stack:    0 pid:  153 ppid:     2 flags:0x0000000a
orkqueue: events_unbound async_run_entry_fn
all trace:
__switch_to+0x120/0x170
blk_mq_run_hw_queue+0x34/0x110
blk_mq_sched_insert_request+0xb0/0x120
blk_execute_rq_nowait+0x68/0x88
blk_execute_rq+0x4c/0xd8
__scsi_execute+0xec/0x1d0
scsi_vpd_inquiry+0x84/0xf0
scsi_get_vpd_buf+0x34/0xb8
scsi_attach_vpd+0x34/0x140
scsi_probe_and_add_lun+0xa6c/0xab8
__scsi_scan_target+0x438/0x4f8
scsi_scan_channel+0x6c/0xa8
scsi_scan_host_selected+0xf0/0x150
do_scsi_scan_host+0x88/0x90
scsi_scan_host+0x1b4/0x1d0
ufshcd_async_scan+0x248/0x310
async_run_entry_fn+0x30/0x178
process_one_work+0x1e8/0x368
worker_thread+0x40/0x478
kthread+0x174/0x180
ret_from_fork+0x10/0x20

Fixes: 8d077ede48c1 ("scsi: ufs: Optimize the command queueing code")
Signed-off-by: Bean Huo <beanhuo@micron.com>
---
 drivers/scsi/ufs/ufshcd.c | 9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
index 6dd517267f1b..15333a327b93 100644
--- a/drivers/scsi/ufs/ufshcd.c
+++ b/drivers/scsi/ufs/ufshcd.c
@@ -1099,19 +1099,21 @@ static int ufshcd_wait_for_doorbell_clr(struct ufs_hba *hba,
 	ktime_t start;
 
 	ufshcd_hold(hba, false);
-	spin_lock_irqsave(hba->host->host_lock, flags);
 	/*
 	 * Wait for all the outstanding tasks/transfer requests.
 	 * Verify by checking the doorbell registers are clear.
 	 */
 	start = ktime_get();
 	do {
+		spin_lock_irqsave(hba->host->host_lock, flags);
 		if (hba->ufshcd_state != UFSHCD_STATE_OPERATIONAL) {
 			ret = -EBUSY;
+			spin_unlock_irqrestore(hba->host->host_lock, flags);
 			goto out;
 		}
-
 		tm_doorbell = ufshcd_readl(hba, REG_UTP_TASK_REQ_DOOR_BELL);
+		spin_unlock_irqrestore(hba->host->host_lock, flags);
+
 		tr_pending = ufshcd_pending_cmds(hba);
 		if (!tm_doorbell && !tr_pending) {
 			timeout = false;
@@ -1120,7 +1122,6 @@ static int ufshcd_wait_for_doorbell_clr(struct ufs_hba *hba,
 			break;
 		}
 
-		spin_unlock_irqrestore(hba->host->host_lock, flags);
 		schedule();
 		if (ktime_to_us(ktime_sub(ktime_get(), start)) >
 		    wait_timeout_us) {
@@ -1132,7 +1133,6 @@ static int ufshcd_wait_for_doorbell_clr(struct ufs_hba *hba,
 			 */
 			do_last_check = true;
 		}
-		spin_lock_irqsave(hba->host->host_lock, flags);
 	} while (tm_doorbell || tr_pending);
 
 	if (timeout) {
@@ -1142,7 +1142,6 @@ static int ufshcd_wait_for_doorbell_clr(struct ufs_hba *hba,
 		ret = -EBUSY;
 	}
 out:
-	spin_unlock_irqrestore(hba->host->host_lock, flags);
 	ufshcd_release(hba);
 	return ret;
 }
-- 
2.25.1