Re: [Open-FCoE] [RFC PATCH] scsi, fcoe, libfc: drop scsi host_lock use from fc_queuecommand

[Mike Christie <michaelc@cs.wisc.edu>]

On 08/31/2010 06:56 PM, Nicholas A. Bellinger wrote:
>> +	if (host->unlocked_qcmds)
>> +		spin_unlock_irqrestore(host->host_lock, flags);
>> +
>>   	if (unlikely(host->shost_state == SHOST_DEL)) {
>>   		cmd->result = (DID_NO_CONNECT<<  16);
>>   		scsi_done(cmd);
>
> I don't think it's safe to call scsi_done() for the SHOST_DEL case here
> with host->unlocked_qcmds=1 w/o holding host_lock, nor would it be safe
> for the SCSI LLD itself using host->unlocked_qcmds=1 to call the
> (*scsi_done)() being passed into sht->queuecommand() without
> host->host_lock being held by either the SCSI ML or the SCSI LLD.

The host state should be checked under the host lock, but I do not think 
it needs to be held with calling scsi_done. scsi_done just queues up the 
request to be completed in the block softirq, and the block layer 
protects against something like the command getting completed by 
multiple code paths/threads.