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

[Doug Ledford]

On Thu, May 04, 2006 at 06:44:35PM +0300, Ishai Rabinovitz wrote:
> 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
> 
> 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.

I'll look into this today and see what I find.

-- 
  Doug Ledford <dledford at redhat.com>
         Red Hat, Inc. 
         1801 Varsity Dr.
         Raleigh, NC 27606