* [PATCH v2] scsi: core: Fix hang of freezing queue between blocking and running device
@ 2021-08-09 14:13 lijinlin3
2021-08-17 7:46 ` Li Jinlin
2021-08-23 16:15 ` Bart Van Assche
0 siblings, 2 replies; 4+ messages in thread
From: lijinlin3 @ 2021-08-09 14:13 UTC (permalink / raw)
To: jejb, martin.petersen, linux-scsi, linux-kernel
Cc: john.garry, bvanassche, qiulaibin, linfeilong, wubo40, lijinlin3
From: Li Jinlin <lijinlin3@huawei.com>
We found a hang issue, the test steps 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 finish this work after step 4, but they hangs.
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--
Step 3 and 4 wait for each other.
To fix this, we need to run queue before rescanning device when the device
state changes to SDEV_RUNNING.
Fixes: f0f82e2476f6 ("scsi: core: Fix capacity set to zero after offlinining device")
Signed-off-by: Li Jinlin <lijinlin3@huawei.com>
Signed-off-by: Qiu Laibin <qiulaibin@huawei.com>
---
changes since v1 send with Message-ID:
20210805143231.1713299-1-lijinlin3@huawei.com
- Modify the subject to make it distinct
- Modify the message to fix typo and make it distinct
- Reduce the number of SOB
drivers/scsi/scsi_sysfs.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/drivers/scsi/scsi_sysfs.c b/drivers/scsi/scsi_sysfs.c
index c3a710bceba0..aa701582c950 100644
--- a/drivers/scsi/scsi_sysfs.c
+++ b/drivers/scsi/scsi_sysfs.c
@@ -809,12 +809,12 @@ 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.
*/
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);
--
2.27.0
^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [PATCH v2] scsi: core: Fix hang of freezing queue between blocking and running device
2021-08-09 14:13 [PATCH v2] scsi: core: Fix hang of freezing queue between blocking and running device lijinlin3
@ 2021-08-17 7:46 ` Li Jinlin
2021-08-23 13:17 ` Li Jinlin
2021-08-23 16:15 ` Bart Van Assche
1 sibling, 1 reply; 4+ messages in thread
From: Li Jinlin @ 2021-08-17 7:46 UTC (permalink / raw)
To: jejb, martin.petersen, linux-scsi, linux-kernel
Cc: john.garry, bvanassche, qiulaibin, linfeilong, wubo40
On 2021/8/9 22:13, Li Jinlin wrote:
> From: Li Jinlin <lijinlin3@huawei.com>
>
> We found a hang issue, the test steps 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 finish this work after step 4, but they hangs.
>
> 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--
>
> Step 3 and 4 wait for each other.
>
> To fix this, we need to run queue before rescanning device when the device
> state changes to SDEV_RUNNING.
>
> Fixes: f0f82e2476f6 ("scsi: core: Fix capacity set to zero after offlinining device")
> Signed-off-by: Li Jinlin <lijinlin3@huawei.com>
> Signed-off-by: Qiu Laibin <qiulaibin@huawei.com>
> ---
> changes since v1 send with Message-ID:
> 20210805143231.1713299-1-lijinlin3@huawei.com
>
> - Modify the subject to make it distinct
> - Modify the message to fix typo and make it distinct
> - Reduce the number of SOB
>
> drivers/scsi/scsi_sysfs.c | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/scsi/scsi_sysfs.c b/drivers/scsi/scsi_sysfs.c
> index c3a710bceba0..aa701582c950 100644
> --- a/drivers/scsi/scsi_sysfs.c
> +++ b/drivers/scsi/scsi_sysfs.c
> @@ -809,12 +809,12 @@ 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.
> */
> 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);
>
>
Ping.
Thanks,
Li Jinlin
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH v2] scsi: core: Fix hang of freezing queue between blocking and running device
2021-08-17 7:46 ` Li Jinlin
@ 2021-08-23 13:17 ` Li Jinlin
0 siblings, 0 replies; 4+ messages in thread
From: Li Jinlin @ 2021-08-23 13:17 UTC (permalink / raw)
To: jejb, martin.petersen, linux-scsi, linux-kernel
Cc: john.garry, bvanassche, qiulaibin, linfeilong, wubo40
On 2021/8/17 16:46, Li Jinlin wrote:
> On 2021/8/9 22:13, Li Jinlin wrote:
>> From: Li Jinlin <lijinlin3@huawei.com>
>>
>> We found a hang issue, the test steps 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 finish this work after step 4, but they hangs.
>>
>> 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--
>>
>> Step 3 and 4 wait for each other.
>>
>> To fix this, we need to run queue before rescanning device when the device
>> state changes to SDEV_RUNNING.
>>
>> Fixes: f0f82e2476f6 ("scsi: core: Fix capacity set to zero after offlinining device")
>> Signed-off-by: Li Jinlin <lijinlin3@huawei.com>
>> Signed-off-by: Qiu Laibin <qiulaibin@huawei.com>
>> ---
>> changes since v1 send with Message-ID:
>> 20210805143231.1713299-1-lijinlin3@huawei.com
>>
>> - Modify the subject to make it distinct
>> - Modify the message to fix typo and make it distinct
>> - Reduce the number of SOB
>>
>> drivers/scsi/scsi_sysfs.c | 6 +++---
>> 1 file changed, 3 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/scsi/scsi_sysfs.c b/drivers/scsi/scsi_sysfs.c
>> index c3a710bceba0..aa701582c950 100644
>> --- a/drivers/scsi/scsi_sysfs.c
>> +++ b/drivers/scsi/scsi_sysfs.c
>> @@ -809,12 +809,12 @@ 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.
>> */
>> 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);
>>
>>
>
> Ping.
>
> Thanks,
> Li Jinlin
>
Hello Guys,
Ping again.
Otherwise, I think that rescan device is not necessary when the device
state changes from blocked to running. Run queue is not necessary either
when the device state changes from offline to running.
I want to add judgment of the old device state before rescanning device
or running queue.
I'd like to know your opinions.
Thanks,
Li Jinlin
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH v2] scsi: core: Fix hang of freezing queue between blocking and running device
2021-08-09 14:13 [PATCH v2] scsi: core: Fix hang of freezing queue between blocking and running device lijinlin3
2021-08-17 7:46 ` Li Jinlin
@ 2021-08-23 16:15 ` Bart Van Assche
1 sibling, 0 replies; 4+ messages in thread
From: Bart Van Assche @ 2021-08-23 16:15 UTC (permalink / raw)
To: lijinlin3, jejb, martin.petersen, linux-scsi, linux-kernel
Cc: john.garry, qiulaibin, linfeilong, wubo40
On 8/9/21 7:13 AM, lijinlin3@huawei.com wrote:
> From: Li Jinlin <lijinlin3@huawei.com>
>
> We found a hang issue, the test steps 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 finish this work after step 4, but they hangs.
>
> 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--
>
> Step 3 and 4 wait for each other.
>
> To fix this, we need to run queue before rescanning device when the device
> state changes to SDEV_RUNNING.
>
> Fixes: f0f82e2476f6 ("scsi: core: Fix capacity set to zero after offlinining device")
> Signed-off-by: Li Jinlin <lijinlin3@huawei.com>
> Signed-off-by: Qiu Laibin <qiulaibin@huawei.com>
> ---
> changes since v1 send with Message-ID:
> 20210805143231.1713299-1-lijinlin3@huawei.com
>
> - Modify the subject to make it distinct
> - Modify the message to fix typo and make it distinct
> - Reduce the number of SOB
>
> drivers/scsi/scsi_sysfs.c | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/scsi/scsi_sysfs.c b/drivers/scsi/scsi_sysfs.c
> index c3a710bceba0..aa701582c950 100644
> --- a/drivers/scsi/scsi_sysfs.c
> +++ b/drivers/scsi/scsi_sysfs.c
> @@ -809,12 +809,12 @@ 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.
> */
> 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);
The patch looks fine to me but I think the comment in
store_state_field() should be expanded. Although the description in the
commit message makes it clear how I/O may hang, that is not clear from
the source code comment. Please mention in the comment that 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.
Thanks,
Bart.
^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2021-08-23 16:15 UTC | newest]
Thread overview: 4+ messages (download: mbox.gz / follow: Atom feed)
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2021-08-09 14:13 [PATCH v2] scsi: core: Fix hang of freezing queue between blocking and running device lijinlin3
2021-08-17 7:46 ` Li Jinlin
2021-08-23 13:17 ` Li Jinlin
2021-08-23 16:15 ` Bart Van Assche
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