linux-kernel - problem with ending requests asynchronously in my block device driver

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Date:	Sat, 15 Dec 2007 13:57:01 -0800 (PST)
From:	a_kumar <cable_plug2000@...oo.com>
To:	linux-kernel@...r.kernel.org
Subject: problem with ending requests asynchronously in my block device
 driver


Hi,

I've a block device driver which does the following,

Inside the request function I do something like this:
request(fn) {

 while ((req = elv_next_request(q)) != NULL) {
....................set up the request;
 spin_unlock_irq(q->queue_lock);
call the transfer(set_up_req) function;
spin_lock_irq(q->queue_lock);
}
       spin_unlock_irq (q->queue_lock);
        /* allow callback to execute as it needs the lock!!! */
        spin_lock_irq (q->queue_lock);


}
and the transfer function calls the scsi_execute_asyn(....) with the
callback function doing the end request. So, the ending of the request is
done like below:

callback(fn) {

 spin_lock_irqsave(q->queue_lock, flags);
        if (!end_that_request_first(set_up_req->req, cmpstatus,
                        set_up_req->req->nr_sectors)) {
                add_disk_randomness(...);
                end_that_request_last(set_up_req->req,0);
        }
        spin_unlock_irqrestore(q->queue_lock, flags);
}


This code works fine with most of the kernel versions, but fails on some
like , Linux 2.6.18-8.el5-xen

Please help me to find out where I'm going wrong?

when I say 'fails' it just hangs without any error ....I'm using dt(Data
test) to write to the disk. The logs show that all the requests that have
been sent for processing, have completed sucessfully. Its just that new
requests never enter the request function. So, the dt writes almost half the
data and then simply hangs.

Thanks in advance for an early reply.
Anil P. 
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