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From: "N.C.Krishna Murthy" <krmurthy@cisco.com>
To: SCSI -DEVELOPERS <linux-scsi@vger.kernel.org>
Subject: two SCSI HBAs having same host no in Linux 2.4 kernel
Date: Wed, 17 Mar 2004 19:40:23 +0530	[thread overview]
Message-ID: <200403171940.23006.krmurthy@cisco.com> (raw)

Hi,
	In 2.4 kernel ,a scsi HBA driver gets it's host no after scsi_register() call 
returns.
The call to scsi_register is made from the driver's 'detect' routine.
scsi_register_host calls the driver's 'detect' routine.

The following is an excerpt from scsi_register_host which does the above job.
-----------------------------------------------------------------------------
if (tpnt->use_new_eh_code) {
                spin_lock_irqsave(&io_request_lock, flags);
                tpnt->present = tpnt->detect(tpnt);
                spin_unlock_irqrestore(&io_request_lock, flags);
        } else
                tpnt->present = tpnt->detect(tpnt);
-----------------------------------------------------------------------------
In case of drivers which do not support new_eh_code, 'detect' is called
without any locks. Is this SMP safe? 

We were testing our iSCSI driver on an SMP machine which had a FC HBA as well.
Both iSCSI driver and FC HBA had the same host no allocated. The behaviour
could not be reproduced consistently though. 

Please let me know in case I am missing something.


Thanx
N.C.Krishna Murthy


             reply	other threads:[~2004-03-17 14:10 UTC|newest]

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2004-03-17 14:10 N.C.Krishna Murthy [this message]
2004-03-17 14:46 ` two SCSI HBAs having same host no in Linux 2.4 kernel Matthew Wilcox
2004-03-17 14:48   ` N.C.Krishna Murthy

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