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From:   Kai-Heng Feng <kai.heng.feng@canonical.com>
To:     jejb@linux.ibm.com, martin.petersen@oracle.com
Cc:     dlemoal@kernel.org, bblock@linux.ibm.com, acelan.kao@canonical.com,
        linux-pm@vger.kernel.org,
        Kai-Heng Feng <kai.heng.feng@canonical.com>,
        linux-scsi@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: [PATCH v5] scsi: core: Wait until device is fully resumed before doing rescan
Date:   Thu,  1 Jun 2023 23:56:52 +0800
Message-Id: <20230601155652.1157611-1-kai.heng.feng@canonical.com>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Precedence: bulk

During system resuming process, the resuming order is from top to down.
Namely, the ATA host is resumed before disks connected to it.

When an EH is scheduled while ATA host is resumed and disk device is
still suspended, the device_lock hold by scsi_rescan_device() is never
released so the dpm_resume() of the disk is blocked forerver, therefore
the system can never be resumed back.

That's because scsi_attach_vpd() is expecting the disk device is in
operational state, as it doesn't work on suspended device.

To avoid such deadlock, wait until the scsi device is fully resumed,
before continuing the rescan process.

Signed-off-by: Kai-Heng Feng <kai.heng.feng@canonical.com>
---
v5:
 - Use a different approach. Wait until the disk device is resumed.

v4: 
 - No change.

v3:
 - New patch to resolve undefined pm_suspend_target_state.

v2:
 - Schedule rescan task at the end of system resume phase.
 - Wording.

 drivers/scsi/scsi_scan.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/scsi/scsi_scan.c b/drivers/scsi/scsi_scan.c
index d217be323cc6..a59aada98ac5 100644
--- a/drivers/scsi/scsi_scan.c
+++ b/drivers/scsi/scsi_scan.c
@@ -1621,6 +1621,9 @@ void scsi_rescan_device(struct device *dev)
 {
 	struct scsi_device *sdev = to_scsi_device(dev);
 
+	if (dev->power.is_suspended)
+		wait_for_completion(&dev->power.completion);
+
 	device_lock(dev);
 
 	scsi_attach_vpd(sdev);
-- 
2.34.1