On 08/06/2009 05:26 AM, Erez Zilber wrote:
> On Wed, Aug 5, 2009 at 10:22 PM, Mike Christie<micha...@cs.wisc.edu> wrote:
>> On 08/05/2009 12:34 PM, Erez Zilber wrote:
>>>> I found it. The problem is that we will send the signal if the xmit
>>>> thread is running or not. If it is not running the workqueue code will
>>>> keep getting woken up to handle the signal, but because we have not
>>>> called queue_work the workqueue code will not let the thread run so we
>>>> never get to flush the signal until we reconnect and send down a login
>>>> pdu (the login pdu does a queue_work finally).
>>>>
>>> When you say "the xmit thread is running", I guess that you mean that
>>> the xmit thread is busy with IO, right? Note that I said that this
>> No. workqueue.c:worker_thread() is spinning. It is looping because there
>> is a signal pending, but the iscsi work code which has the flush_signals
>> is not getting run because there is no work queued.
>>
>> So you could add a
>>
>> if (signal_pending(current))
>> flush_signals(current)
>>
>> to worker_thread() "for" loop and I think this will fix the problem.
>>
>
> Looks like this solves the problem. I've added the following patch to
> the centos 5.3 kernel (2.6.18-128.1.6.el5):
>
> diff --git a/kernel/workqueue.c b/kernel/workqueue.c
> index 8594efb..e148ed8 100644
> --- a/kernel/workqueue.c
> +++ b/kernel/workqueue.c
> @@ -253,6 +253,9 @@ static int worker_thread(void *__cwq)
>
> set_current_state(TASK_INTERRUPTIBLE);
> while (!kthread_should_stop()) {
> + if (signal_pending(current))
> + flush_signals(current);
> +
> add_wait_queue(&cwq->more_work,&wait);
> if (list_empty(&cwq->worklist))
> schedule();
>
> I'm running with open-iscsi.git + 2 commits from linux-2.6-iscsi.git
> (9c302cc45b70ecc4b606d65a445902381066061b&
> 75be23dc40ba2f215779d5ba60fda9a762271bbe).
>
> Will you push it upstream& into the RHEL kernel?
>
I am not sure. I was thinking that switching from a workqueue to a
thread is the right thing to do. The drawback is that the workqueue is
nice when there are multiple sessions for a host like is done with
bnx2i, cxgb3i and be_iscsi. I can just queue_work and pass the
connection to send on. If I switch to a work_queue I have to add my own
code to do that.
I am going to post a patch like you did to linux-kernel and see what
people say is best. If it goes in then I will port to RHEL.
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