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SubjectRe: Patch added to scsi-rc-fixes-2.6: [SCSI] host lock push-down
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On Wed, 2010-11-10 at 18:52 -0500, Jeff Garzik wrote:
> On 11/10/2010 06:45 PM, James Bottomley wrote:
> > On Wed, 2010-11-10 at 18:28 -0500, Jeff Garzik wrote:
> >> On 11/10/2010 05:40 PM, James Bottomley wrote:
> >>> Your commit:
> >>>
> >>> [SCSI] host lock push-down
> >>>
> >>> Move the mid-layer's ->queuecommand() invocation from being locked
> >>> with the host lock to being unlocked to facilitate speeding up the
> >>> critical path for drivers who don't need this lock taken anyway.
> >>>
> >>> The patch below presents a simple SCSI host lock push-down as an
> >>> equivalent transformation. No locking or other behavior should change
> >>> with this patch. All existing bugs and locking orders are preserved.
> >>>
> >>> Minimal code disturbance was attempted with this change. Most drivers
> >>> needed only two one-line modifications for their host lock push-down.
> >>>
> >>> Signed-off-by: Jeff Garzik<jgarzik@redhat.com>
> >>> Signed-off-by: James Bottomley<James.Bottomley@suse.de>
> >>>
> >>> has been added to the upstream SCSI tree
> >>> You can find it here:
> >>
> >> No comments on renaming ->queuecommand to something else?
> >
> > What we wondered about doing differently isn't really relevant for a
> > change log ... that should just really be about what was done (to avoid
> > confusion).
>
> Wasn't referring to the changelog (perhaps shouldn't have quoted that);
> just asking the question generally.
>
>
> >> The consequences are rather dire if this goes unnoticed, yes?
> >
> > You mean if there's a missed in-tree driver? Yes, but I took care to
> > make sure all SCSI drivers were accounted for. For out of tree drivers,
> > as with the eh lock push down, it's caveat emptor.
>
> Thinking about out-of-tree drivers, yes.
>

Hi Jeff and James,

Thank you for getting this initial patch merged. I really think this
was and is the best choice moving forward. Also, a seriously big thank
you to all of the other folks who have helped identify LLDs issues for
host_lock less mode for drivers!!

In the next days I will get a atomic_t scsi_host->cmd_serial_number
patch rebased (which is really very minor at this point w/o the
scsi_error.c changes), and merge the current host_lock-less 'scoreboard'
on top of jgarzik's code and tag for .38. So, please let me know if
you would to include minor the atomic_t scsi_host->cmd_serial_number
patch for .37 or if you would rather have this immediately preceed the
first series of "enable host-lock_less for LLD vendor superturbo hba"
for the .38 round.

Best,

--nab



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