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SubjectRE: [PATCH] SCSI driver for VMware's virtual HBA - V3.
> -----Original Message-----
> From: linux-kernel-owner@vger.kernel.org [mailto:linux-kernel-
> owner@vger.kernel.org] On Behalf Of Brian King
> Sent: Thursday, September 03, 2009 5:53 PM
> To: akataria@vmware.com
> Cc: James Bottomley; Rolf Eike Beer; Matthew Wilcox; Roland Dreier; Bart
> Van Assche; Robert Love; Randy Dunlap; Mike Christie; linux-
> scsi@vger.kernel.org; LKML; Andrew Morton; pv-drivers@vmware.com
> Subject: Re: [PATCH] SCSI driver for VMware's virtual HBA - V3.
>
> Alok Kataria wrote:
> > +
> > +struct pvscsi_adapter {
> > + char *mmioBase;
> > + unsigned int irq;
> > + u8 rev;
> > + bool use_msi;
> > + bool use_msix;
> > + bool use_msg;
> > +
> > + spinlock_t hw_lock;
>
> Why not just use host_lock in the scsi_host structure?
>

Why not an adapter_resource_lock? Why block everyone @ the scsi-mid layer.

Alok,

(This is just a optimization.You don't need it in order to get your code merged upstream.You can always patch it later on)In fact hw_lock should be split into two locks -

req_path_lock(aka tx_lock) and
cmpl_path_lock(aka rx_lock).

You can then have a full-duplex channel.

Revised-code -
::pvscsi_acquire_context->spin_lock_irqsave(tx_lock)
::pvscsi_isr->spin_lock_irqsave(rx_lock)
::some_future_napi_style_pvrx_poll_func->spin_lock_irqsave(rx_lock)

::for aborts synchronize on the rx_lock so that you know what's completed and what's not.

This is the kind of common code that should be provided by the bottom edge of the scsi-layer so that all the scsi-LLDD's can split their tx/rx paths!




> Brian King
> Linux on Power Virtualization
> IBM Linux Technology Center
>


Chetan


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