Date: Sun, 21 Nov 2004 09:56:36 +0100
From: Jens Axboe <axboe@suse.de>
To: Alan Chandler <alan@chandlerfamily.org.uk>
Cc: linux-kernel@vger.kernel.org
Subject: Re: ide-cd problem
Message-ID: <20041121085636.GG26240@suse.de>
References: <200411201842.15091.alan@chandlerfamily.org.uk> <20041120194756.GU26240@suse.de> <200411210053.45065.alan@chandlerfamily.org.uk>
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On Sun, Nov 21 2004, Alan Chandler wrote:
> On Saturday 20 November 2004 19:47, Jens Axboe wrote:
> > On Sat, Nov 20 2004, Alan Chandler wrote:
> ...
> > > Normally, because the requested data_len is not zero, the data is
> > > sent.  In this case however, because the original request had nothing
> > > to send, the while/if clauses to initiate a new transfer are skipped
> > > and the routine ends up setting a new interrupt handler address and
> > > returning to await an interrupt that will never come.
> >
> > The big question is - what does the original command look like? Just
> > dumping rq->cmd[0] would be a big help, but really just put code in
> > sg_io() in block/scsi_ioctl.c to dump the completed sg_io_hdr_t and send
> > that.
> 
> I haven't dumped the whole request header, but the command (after it has been 
> retrieved from the user) and the dxfer_length.  Is there anything else I 
> should dump?

No that's fine, that's all I need.

> Here is the output leading up to the point where ide-cd hangs because the IO 
> is just left pending
> 
> Nov 21 00:44:20 kanger kernel: sg_io command length 10
> Nov 21 00:44:20 kanger kernel: sg_io command [0] = 0x3c
> Nov 21 00:44:20 kanger kernel: sg_io command [1] = 0x0
> Nov 21 00:44:20 kanger kernel: sg_io command [2] = 0x0
> Nov 21 00:44:20 kanger kernel: sg_io command [3] = 0x0
> Nov 21 00:44:20 kanger kernel: sg_io command [4] = 0x0
> Nov 21 00:44:20 kanger kernel: sg_io command [5] = 0x0
> Nov 21 00:44:20 kanger kernel: sg_io command [6] = 0x0
> Nov 21 00:44:20 kanger kernel: sg_io command [7] = 0xfc
> Nov 21 00:44:20 kanger kernel: sg_io command [8] = 0x0
> Nov 21 00:44:20 kanger kernel: sg_io command [9] = 0x0
> Nov 21 00:44:20 kanger kernel: sg_io dxfer_len = 64512
> Nov 21 00:44:20 kanger kernel: sg_io command length 10
> Nov 21 00:44:20 kanger kernel: sg_io command [0] = 0x3c
> Nov 21 00:44:20 kanger kernel: sg_io command [1] = 0x0
> Nov 21 00:44:20 kanger kernel: sg_io command [2] = 0x0
> Nov 21 00:44:20 kanger kernel: sg_io command [3] = 0x0
> Nov 21 00:44:20 kanger kernel: sg_io command [4] = 0x0
> Nov 21 00:44:20 kanger kernel: sg_io command [5] = 0x0
> Nov 21 00:44:20 kanger kernel: sg_io command [6] = 0x0
> Nov 21 00:44:20 kanger kernel: sg_io command [7] = 0xfc
> Nov 21 00:44:20 kanger kernel: sg_io command [8] = 0x0
> Nov 21 00:44:20 kanger kernel: sg_io command [9] = 0x0
> Nov 21 00:44:20 kanger kernel: sg_io dxfer_len = 64512
> Nov 21 00:44:20 kanger kernel: sg_io command length 10
> Nov 21 00:44:20 kanger kernel: sg_io command [0] = 0x3c
> Nov 21 00:44:20 kanger kernel: sg_io command [1] = 0x0
> Nov 21 00:44:20 kanger kernel: sg_io command [2] = 0x0
> Nov 21 00:44:20 kanger kernel: sg_io command [3] = 0x0
> Nov 21 00:44:20 kanger kernel: sg_io command [4] = 0x0
> Nov 21 00:44:20 kanger kernel: sg_io command [5] = 0x0
> Nov 21 00:44:20 kanger kernel: sg_io command [6] = 0x0
> Nov 21 00:44:20 kanger kernel: sg_io command [7] = 0xfc
> Nov 21 00:44:20 kanger kernel: sg_io command [8] = 0x0
> Nov 21 00:44:20 kanger kernel: sg_io command [9] = 0x0
> Nov 21 00:44:20 kanger kernel: sg_io dxfer_len = 64512
> Nov 21 00:44:20 kanger kernel: sg_io command length 10
> Nov 21 00:44:20 kanger kernel: sg_io command [0] = 0x3c
> Nov 21 00:44:20 kanger kernel: sg_io command [1] = 0x0
> Nov 21 00:44:20 kanger kernel: sg_io command [2] = 0x0
> Nov 21 00:44:20 kanger kernel: sg_io command [3] = 0x0
> Nov 21 00:44:20 kanger kernel: sg_io command [4] = 0x0
> Nov 21 00:44:20 kanger kernel: sg_io command [5] = 0x0
> Nov 21 00:44:20 kanger kernel: sg_io command [6] = 0x0
> Nov 21 00:44:20 kanger kernel: sg_io command [7] = 0xfc
> Nov 21 00:44:20 kanger kernel: sg_io command [8] = 0x0
> Nov 21 00:44:20 kanger kernel: sg_io command [9] = 0x0
> Nov 21 00:44:20 kanger kernel: sg_io dxfer_len = 64512
> Nov 21 00:44:20 kanger kernel: sg_io command length 6
> Nov 21 00:44:20 kanger kernel: sg_io command [0] = 0x0
> Nov 21 00:44:20 kanger kernel: sg_io command [1] = 0x0
> Nov 21 00:44:20 kanger kernel: sg_io command [2] = 0x0
> Nov 21 00:44:20 kanger kernel: sg_io command [3] = 0x0
> Nov 21 00:44:20 kanger kernel: sg_io command [4] = 0x0
> Nov 21 00:44:20 kanger kernel: sg_io command [5] = 0x0
> Nov 21 00:44:20 kanger kernel: sg_io dxfer_len = 0
> Nov 21 00:44:20 kanger kernel: sg_io command length 6
> Nov 21 00:44:20 kanger kernel: sg_io command [0] = 0x1b
> Nov 21 00:44:20 kanger kernel: sg_io command [1] = 0x0
> Nov 21 00:44:20 kanger kernel: sg_io command [2] = 0x0
> Nov 21 00:44:20 kanger kernel: sg_io command [3] = 0x0
> Nov 21 00:44:20 kanger kernel: sg_io command [4] = 0x3
> Nov 21 00:44:20 kanger kernel: sg_io command [5] = 0x0
> Nov 21 00:44:20 kanger kernel: sg_io dxfer_len = 0
> Nov 21 00:45:00 kanger kernel: hdc: lost interrupt
> Nov 21 00:45:40 kanger kernel: hdc: lost interrupt
> Nov 21 00:47:00 kanger last message repeated 2 times
> Nov 21 00:47:40 kanger kernel: hdc: lost interrupt

So the last request is a START_STOP unit, which doesn't transfer any
data. If the drive has DRQ_STAT stat set here, it looks very odd. Any
chance you could instrument cdrom_newpc_intr() as well to dump status
bytes and expected transfer lengths from the drive?

-- 
Jens Axboe

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