On Wed, 2010-11-17 at 12:21 -0500, Jeff Garzik wrote:
> Much better... Just updated #upstream-fixes with the below patch.
>
> James just posted to linux-scsi
> [PATCH] Eliminate error handler overload of the SCSI serial number
> but as Tejun pointed out, we _completely and entirely_ replace the SCSI
> error handler apparatus with our own, thereby eliminating any
> possibility that we would ever read or use cmd->serial_number.
>
> Our lock profile is quite a bit improved.
>
> Further simplifications and cleanups related to 'done' are possible,
> but those are kept separate from the change below.
>
>
> commit 23e701e6208191ad103517ae7a700f2dc59ab2ec
> Author: Jeff Garzik <jeff@xxxxxxxxxx>
> Date: Wed Nov 17 12:03:58 2010 -0500
>
> [libata] remove SCSI host lock and serial number usage from ata_scsi_queuecmd
>
> cmd->serial_number is never tested in any path we reach; therefore we may
> remove the call to scsi_cmd_get_serial() inside DEF_SCSI_QCMD, the SCSI
> host_lock acquisition surrounding it, and our own SCSI host_lock
> unlock+relock cycle.
>
> Signed-off-by: Jeff Garzik <jgarzik@xxxxxxxxxx>
Hi Jeff,
I have merged this patch into lock_less-LLDs-for-38-v2, and dropped the
original:
[PATCH 02/12] libata: Convert to host_lock less w/ interrupts disabled internally
Thanks!
--nab
>
> drivers/ata/libata-scsi.c | 21 +++++++++------------
> 1 file changed, 9 insertions(+), 12 deletions(-)
>
> diff --git a/drivers/ata/libata-scsi.c b/drivers/ata/libata-scsi.c
> index 19835d3..66aa4be 100644
> --- a/drivers/ata/libata-scsi.c
> +++ b/drivers/ata/libata-scsi.c
> @@ -3166,8 +3166,8 @@ static inline int __ata_scsi_queuecmd(struct scsi_cmnd *scmd,
>
> /**
> * ata_scsi_queuecmd - Issue SCSI cdb to libata-managed device
> + * @shost: SCSI host of command to be sent
> * @cmd: SCSI command to be sent
> - * @done: Completion function, called when command is complete
> *
> * In some cases, this function translates SCSI commands into
> * ATA taskfiles, and queues the taskfiles to be sent to
> @@ -3177,42 +3177,39 @@ static inline int __ata_scsi_queuecmd(struct scsi_cmnd *scmd,
> * ATA and ATAPI devices appearing as SCSI devices.
> *
> * LOCKING:
> - * Releases scsi-layer-held lock, and obtains host lock.
> + * ATA host lock
> *
> * RETURNS:
> * Return value from __ata_scsi_queuecmd() if @cmd can be queued,
> * 0 otherwise.
> */
> -static int ata_scsi_queuecmd_lck(struct scsi_cmnd *cmd, void (*done)(struct scsi_cmnd *))
> +int ata_scsi_queuecmd(struct Scsi_Host *shost, struct scsi_cmnd *cmd)
> {
> struct ata_port *ap;
> struct ata_device *dev;
> struct scsi_device *scsidev = cmd->device;
> - struct Scsi_Host *shost = scsidev->host;
> int rc = 0;
> + unsigned long irq_flags;
>
> ap = ata_shost_to_port(shost);
>
> - spin_unlock(shost->host_lock);
> - spin_lock(ap->lock);
> + spin_lock_irqsave(ap->lock, irq_flags);
>
> ata_scsi_dump_cdb(ap, cmd);
>
> dev = ata_scsi_find_dev(ap, scsidev);
> if (likely(dev))
> - rc = __ata_scsi_queuecmd(cmd, done, dev);
> + rc = __ata_scsi_queuecmd(cmd, cmd->scsi_done, dev);
> else {
> cmd->result = (DID_BAD_TARGET << 16);
> - done(cmd);
> + cmd->scsi_done(cmd);
> }
>
> - spin_unlock(ap->lock);
> - spin_lock(shost->host_lock);
> + spin_unlock_irqrestore(ap->lock, irq_flags);
> +
> return rc;
> }
>
> -DEF_SCSI_QCMD(ata_scsi_queuecmd)
> -
> /**
> * ata_scsi_simulate - simulate SCSI command on ATA device
> * @dev: the target device
> --
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