On Fri, Mar 22, 2019 at 09:45:54AM +0800, zhengbin wrote: > When I use dd test a SCSI device which use blk-mq in the following steps: > 1.echo "blocked" >/sys/block/sda/device/state > 2.dd if=/dev/sda of=/mnt/t.log bs=1M count=10 > 3.echo "running" >/sys/block/sda/device/state > dd should finish this work after step 3, unfortunately, still hung. > > After step2, the key code process is like this: > blk_mq_dispatch_rq_list-->scsi_queue_rq-->prep_to_mq > > prep_to_mq will return BLK_STS_RESOURCE, and scsi_queue_rq will transter > it to BLK_STS_DEV_RESOURCE, which means that driver can guarantee that > IO dispatch will be triggered in future when the resource is available. > Need to follow the rule if we set the device state to running. > > Signed-off-by: zhengbin <zhengbin13@xxxxxxxxxx> > --- > drivers/scsi/scsi_sysfs.c | 5 +++++ > 1 file changed, 5 insertions(+) > > diff --git a/drivers/scsi/scsi_sysfs.c b/drivers/scsi/scsi_sysfs.c > index 6a9040f..266e4c7 100644 > --- a/drivers/scsi/scsi_sysfs.c > +++ b/drivers/scsi/scsi_sysfs.c > @@ -772,6 +772,11 @@ store_state_field(struct device *dev, struct device_attribute *attr, > mutex_lock(&sdev->state_mutex); > ret = scsi_device_set_state(sdev, state); > mutex_unlock(&sdev->state_mutex); > + /* If device state changes to SDEV_RUNNING, we need to run hw queue > + * to avoid io hung. > + */ > + if (ret == 0 && state == SDEV_RUNNING) > + blk_mq_run_hw_queues(sdev->request_queue, true); > Thinking of further, this way isn't safe, given the caller should make sure that the queue is alive before calling blk_mq_run_hw_queues(). Now it is in sysfs write path, and the scsi device can become gone just before calling blk_mq_run_hw_queues(). Thanks, Ming
