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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Vaibhav Jain <vaibhav@linux.ibm.com>,
        "Martin K. Petersen" <martin.petersen@oracle.com>
Subject: [PATCH 4.20 337/352] scsi: cxlflash: Prevent deadlock when adapter probe fails
Date:   Mon, 11 Feb 2019 15:19:24 +0100
Message-Id: <20190211141908.563842445@linuxfoundation.org>
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4.20-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Vaibhav Jain <vaibhav@linux.ibm.com>

commit bb61b843ffd46978d7ca5095453e572714934eeb upstream.

Presently when an error is encountered during probe of the cxlflash
adapter, a deadlock is seen with cpu thread stuck inside
cxlflash_remove(). Below is the trace of the deadlock as logged by
khungtaskd:

cxlflash 0006:00:00.0: cxlflash_probe: init_afu failed rc=-16
INFO: task kworker/80:1:890 blocked for more than 120 seconds.
       Not tainted 5.0.0-rc4-capi2-kexec+ #2
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
kworker/80:1    D    0   890      2 0x00000808
Workqueue: events work_for_cpu_fn

Call Trace:
 0x4d72136320 (unreliable)
 __switch_to+0x2cc/0x460
 __schedule+0x2bc/0xac0
 schedule+0x40/0xb0
 cxlflash_remove+0xec/0x640 [cxlflash]
 cxlflash_probe+0x370/0x8f0 [cxlflash]
 local_pci_probe+0x6c/0x140
 work_for_cpu_fn+0x38/0x60
 process_one_work+0x260/0x530
 worker_thread+0x280/0x5d0
 kthread+0x1a8/0x1b0
 ret_from_kernel_thread+0x5c/0x80
INFO: task systemd-udevd:5160 blocked for more than 120 seconds.

The deadlock occurs as cxlflash_remove() is called from cxlflash_probe()
without setting 'cxlflash_cfg->state' to STATE_PROBED and the probe thread
starts to wait on 'cxlflash_cfg->reset_waitq'. Since the device was never
successfully probed the 'cxlflash_cfg->state' never changes from
STATE_PROBING hence the deadlock occurs.

We fix this deadlock by setting the variable 'cxlflash_cfg->state' to
STATE_PROBED in case an error occurs during cxlflash_probe() and just
before calling cxlflash_remove().

Cc: stable@vger.kernel.org
Fixes: c21e0bbfc485("cxlflash: Base support for IBM CXL Flash Adapter")
Signed-off-by: Vaibhav Jain <vaibhav@linux.ibm.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/scsi/cxlflash/main.c |    2 ++
 1 file changed, 2 insertions(+)

--- a/drivers/scsi/cxlflash/main.c
+++ b/drivers/scsi/cxlflash/main.c
@@ -3694,6 +3694,7 @@ static int cxlflash_probe(struct pci_dev
 	host->max_cmd_len = CXLFLASH_MAX_CDB_LEN;
 
 	cfg = shost_priv(host);
+	cfg->state = STATE_PROBING;
 	cfg->host = host;
 	rc = alloc_mem(cfg);
 	if (rc) {
@@ -3782,6 +3783,7 @@ out:
 	return rc;
 
 out_remove:
+	cfg->state = STATE_PROBED;
 	cxlflash_remove(pdev);
 	goto out;
 }