On Fri, Mar 22, 2019 at 10:18:54AM +0800, zhengbin (A) wrote: > So blk_mq_run_hw_queues should still be in mutex_lock(&sdev->state_mutex)?? I think so, this way should be safe given the pattern is used in __scsi_remove_device() already. BTW, please do not reply before the quoted text, and I'd suggest you to read some linux kernel development FAQ: http://vger.kernel.org/lkml/#s3-9 Thanks, Ming > > On 2019/3/22 10:11, Ming Lei wrote: > > 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 > > > > . > > >
