[openfabrics-ewg] Current OFED kernel snapshot - problems in backporting SRP to RH4

[Ishai Rabinovitz]

On Wed, May 03, 2006 at 12:07:19AM +0300, Doug Ledford wrote:
> On Tue, May 02, 2006 at 11:30:13AM +0300, Ishai Rabinovitz wrote:
> > We have a problem when trying to back port SRP to RH4 U2 and U3 (Actually to 
> > any kernel earlier than 2.6.13).
> > The problem is when the SCSI driver is calling to eh_abort_handler,
> > or to eh_device_reset_handler.
> > In the current kernel (starting from 2.6.13) this call is made without 
> > host_lock spin-lock locked.
> > In the SRP code that performs the abort and the reset (srp_send_tsk_mgmt) we 
> > send a message to the target and we wait for a response from the target.
> > 
> > In early versions of the kernel the SCSI driver performs irq_spinlock_save to 
> > the host_lock before calling to the abort or reset handlers.
> > This creates a problem: The SRP driver can not go to sleep until the target will
> > answer.
> 
> 
> static int srp_abort(struct scsi_cmnd *scmnd)
> {
> 	int rv;
>         printk(KERN_ERR "SRP abort called\n");
> 
> 	spin_unlock_irq(scmnd->device->host->host_lock);
>         rv = srp_send_tsk_mgmt(scmnd, SRP_TSK_ABORT_TASK);
>         spin_lock_irq(scmnd->device->host->host_lock);
> 	return rv;
> }
> 
> repeat the same change for srp_reset and srp_reset_host
> 
> -- 
>   Doug Ledford <dledford at redhat.com>
>          Red Hat, Inc. 
>          1801 Varsity Dr.
>          Raleigh, NC 27606
>   
> _______________________________________________
> openfabrics-ewg mailing list
> openfabrics-ewg at openib.org
> http://openib.org/mailman/listinfo/openfabrics-ewg

Do you think that there is a chance that in RedHat EL4 up4 the SCSI driver will behave
like in recent kernels, meaning it will not lock the spin lock?

This will make it possible to support SRP in RedHat EL4 up4.
-- 
Ishai Rabinovitz