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| author | Li Jinlin <lijinlin3@huawei.com> | 2021-08-24 05:59:21 +0300 |
|---|---|---|
| committer | Martin K. Petersen <martin.petersen@oracle.com> | 2021-08-25 06:06:19 +0300 |
| commit | 02c6dcd543f8f051973ee18bfbc4dc3bd595c558 (patch) | |
| tree | 608405e6f1118255876e38941b7a1881f59111a7 /drivers/scsi/scsi_sysfs.c | |
| parent | 40d32727931cee82cdc5aaca25ce725d1f3ac864 (diff) | |
| download | linux-02c6dcd543f8f051973ee18bfbc4dc3bd595c558.tar.xz | |
scsi: core: Fix hang of freezing queue between blocking and running device
We found a hang, the steps to reproduce are as follows:
1. blocking device via scsi_device_set_state()
2. dd if=/dev/sda of=/mnt/t.log bs=1M count=10
3. echo none > /sys/block/sda/queue/scheduler
4. echo "running" >/sys/block/sda/device/state
Step 3 and 4 should complete after step 4, but they hang.
CPU#0 CPU#1 CPU#2
--------------- ---------------- ----------------
Step 1: blocking device
Step 2: dd xxxx
^^^^^^ get request
q_usage_counter++
Step 3: switching scheculer
elv_iosched_store
elevator_switch
blk_mq_freeze_queue
blk_freeze_queue
> blk_freeze_queue_start
^^^^^^ mq_freeze_depth++
> blk_mq_run_hw_queues
^^^^^^ can't run queue when dev blocked
> blk_mq_freeze_queue_wait
^^^^^^ Hang here!!!
wait q_usage_counter==0
Step 4: running device
store_state_field
scsi_rescan_device
scsi_attach_vpd
scsi_vpd_inquiry
__scsi_execute
blk_get_request
blk_mq_alloc_request
blk_queue_enter
^^^^^^ Hang here!!!
wait mq_freeze_depth==0
blk_mq_run_hw_queues
^^^^^^ dispatch IO, q_usage_counter will reduce to zero
blk_mq_unfreeze_queue
^^^^^ mq_freeze_depth--
To fix this, we need to run queue before rescanning device when the device
state changes to SDEV_RUNNING.
Link: https://lore.kernel.org/r/20210824025921.3277629-1-lijinlin3@huawei.com
Fixes: f0f82e2476f6 ("scsi: core: Fix capacity set to zero after offlinining device")
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Li Jinlin <lijinlin3@huawei.com>
Signed-off-by: Qiu Laibin <qiulaibin@huawei.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Diffstat (limited to 'drivers/scsi/scsi_sysfs.c')
| -rw-r--r-- | drivers/scsi/scsi_sysfs.c | 9 |
1 files changed, 6 insertions, 3 deletions
diff --git a/drivers/scsi/scsi_sysfs.c b/drivers/scsi/scsi_sysfs.c index ae9bfc658203..c0d31119d6d7 100644 --- a/drivers/scsi/scsi_sysfs.c +++ b/drivers/scsi/scsi_sysfs.c @@ -808,12 +808,15 @@ store_state_field(struct device *dev, struct device_attribute *attr, ret = scsi_device_set_state(sdev, state); /* * If the device state changes to SDEV_RUNNING, we need to - * rescan the device to revalidate it, and run the queue to - * avoid I/O hang. + * run the queue to avoid I/O hang, and rescan the device + * to revalidate it. Running the queue first is necessary + * because another thread may be waiting inside + * blk_mq_freeze_queue_wait() and because that call may be + * waiting for pending I/O to finish. */ if (ret == 0 && state == SDEV_RUNNING) { - scsi_rescan_device(dev); blk_mq_run_hw_queues(sdev->request_queue, true); + scsi_rescan_device(dev); } mutex_unlock(&sdev->state_mutex); |