Hi,
On Thu, May 20, 2010 at 3:32 PM, Tejun Heo <tj@xxxxxxxxxx> wrote:
> On 05/17/2010 01:32 PM, Prashant wrote:
>> Hi,
>> I have a board with backplane for SATA disks. Sometimes when I unplug
>> a disk while
>> IO is going on, I get following problem. Has anybody of you
>> experienced this before?
>> Sometimes spinlock owner is kblockd, sometimes it is scsi_eh.
>
> Sorry but 2.6.24 is way too ancient at this point and too much has
> changed. Can you please try a recent kernel and see whether the
> problem is reproducible?
>
Okay I 'll update If I get same problem with latest kernel (will take
lot of time).
I have a question related to code which is almost same in the current kernel.
I don't know whether this is the right mailing list for the following question.
When a sata drive is unplugged, its corresponding sdev's state is set
to SDEV_OFFLINE. Now if IO requests are still comming on the same device,
They will be killed by calling scsi_kill_request().
1) scsi_kill_request does following things:
i) Unlock request queue
ii) Increment host_busy count
iii) Lock request queue
iv) Calls __scsi_done()
2) __scsi_done() does following things:
i) set request completion data
ii) Calls blk_completion_request()
3) blk_completion_request() does following things:
i) Adds request->donelist to blk_cpu_done softirq queue
and raise the softirq (which is scsi_softirq_done)
4) next sequence is:
scsi_softirq_done >> scsi_finish_command >> scsi_device_unbusy()
5) scsi_device_unbusy() again locks the request_queue. This is the place where
we can get into the spinlock recursion.
Is this correct? Please correct me if something is wrong.
Thanks,
Prashant
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