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    SubjectRe: Patch added to scsi-rc-fixes-2.6: [SCSI] host lock push-down
    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<>
    > >>> Signed-off-by: James Bottomley<>
    > >>>
    > >>> 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.



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