From mboxrd@z Thu Jan  1 00:00:00 1970
From: Mike Christie <michaelc@cs.wisc.edu>
Subject: Re: [PATCH 01/11] libiscsi: Convert to host_lock less w/ interrupts
 disabled internally
Date: Thu, 18 Nov 2010 12:26:59 -0600
Message-ID: <4CE56FF3.300@cs.wisc.edu>
References: <1290032304-4859-1-git-send-email-nab@linux-iscsi.org> <4CE47C12.80804@cs.wisc.edu> <4CE4F906.3080506@panasas.com>
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To: Boaz Harrosh <bharrosh@panasas.com>
Cc: "Nicholas A. Bellinger" <nab@linux-iscsi.org>, linux-scsi <linux-scsi@vger.kernel.org>, Jeff Garzik <jeff@garzik.org>, James Bottomley <James.Bottomley@suse.de>, Christoph Hellwig <hch@lst.de>, Ravi Anand <ravi.anand@qlogic.com>, Andrew Vasquez <andrew.vasquez@qlogic.com>, Joe Eykholt <jeykholt@cisco.com>, James Smart <james.smart@emulex.com>, Vasu Dev <vasu.dev@linux.intel.com>, Tim Chen <tim.c.chen@linux.intel.com>, Andi Kleen <ak@linux.intel.com>, Tejun Heo <tj@kernel.org>, Mike Anderson <andmike@linux.vnet.ibm.com>, MPTFusionLinux <DL-MPTFusionLinux@lsi.com>

On 11/18/2010 03:59 AM, Boaz Harrosh wrote:
> On 11/18/2010 03:06 AM, Mike Christie wrote:
>> On 11/17/2010 04:18 PM, Nicholas A. Bellinger wrote:
>>>    prepd_fault:
>>>    	sc->scsi_done = NULL;
>>
>>> -	done(sc);
>>> -	spin_lock(host->host_lock);
>>> +	sc->scsi_done(sc);
>>>    	return 0;
>>
>> This will NULL pointer. See a couple lines above where we NULL it.
>> iscsi_free_task checks if the scsi_done pointer is set and if it is it
>> will call scsi_done.
>>
>> It is a hack to prevent the normal completion path from calling
>> scsi_done. For the case where we return SCSI_MLQUEUE_TARGET_BUSY (the
>> prepd_reject case) we need something to prevent scsi_done from getting
>> called.
>>
>> For the return 0/prepd_fault case we can just call sc->scsi_done, but we
>> have to move some code around.
>>
>> I do not like how the code does the NULLing and testing. Let me work on
>> this and send a tested patch.
>
> Mike if you are on this. Do you think we need the _irqsave locking.
> I always thought that the network receive is not on the HW interrupt
> but on a completion thread. Could you verify?
>

Yeah, we do not need the irqsave locking, because for software iscsi the 
session lock is just locked in softirqs/timers and the iscsi xmit 
thread. For offload and iser (be2iscsi, bnx2i, iser and cxgb*) we have 
similar combinations (some drivers have a tasklet thrown in there too) 
and no real interrupts.

qla4xxx does not use the iscsi_queuecommand function.