linux-kernel - Re: [PATCH] scsi: Convert scsi_host->cmd_serial_number to odd numbered atomic

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Date:	Thu, 11 Nov 2010 14:36:50 -0800
From:	Mike Anderson <andmike@...ux.vnet.ibm.com>
To:	James Bottomley <James.Bottomley@...e.de>
Cc:	"Nicholas A. Bellinger" <nab@...ux-iscsi.org>,
	linux-scsi <linux-scsi@...r.kernel.org>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	Jeff Garzik <jeff@...zik.org>, Christoph Hellwig <hch@....de>
Subject: Re: [PATCH] scsi: Convert scsi_host->cmd_serial_number to odd
 numbered atomic_t counter

James Bottomley <James.Bottomley@...e.de> wrote:
> On Thu, 2010-11-11 at 13:37 -0800, Nicholas A. Bellinger wrote:
> >
> >  ..snip..
> >
> > Sounds good to me, but you will recall the last attempt to make
> > scsi_cmd_get_serial() optional for the special case LLDs, that we
> > started running quickly in the legacy usage of cmd->serial_number in
> > scsi_softirq_done() and the side effects in scsi_try_to_abort_cmd(), who
> > use is complex enough that we have not found a proper resolution
> > sufficent to andmike discussed here:
> 
> Yes, that's what I meant by "eliminate the overloading of the serial
> number zero value" above.  This needs fixing before the serial number
> can be dumped for fast hba drivers.
> 

In the last email referenced below I believed that since
scsi_softirq_done is calling scsi_eh_scmd_add without the
SCSI_EH_CANCEL_CMD flag set this will stop scsi_try_to_abort_cmd from
being called. Since scsi_softirq_done is the one setting serial_number
to 0 I do not believe we can hit the serial number == 0 check in
scsi_try_to_abort_cmd anymore.

> > http://marc.info/?l=linux-scsi&m=128820726325009&w=2

-andmike
--
Michael Anderson
andmike@...ux.vnet.ibm.com
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