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SCSI host lock push-down

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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.

Additionally, add one parameter to queuecommand,
	struct Scsi_Host *
and remove one parameter from queuecommand,
	void (*done)(struct scsi_cmnd *)

Scsi_Host* is a convenient pointer that most host drivers need anyway,
and 'done' is redundant to struct scsi_cmnd->scsi_done.

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>
Acked-by: James Bottomley <James.Bottomley@suse.de>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Jeff Garzik
2010-11-16 02:10:29 -05:00
committed by Linus Torvalds
parent bdbd01ac44
commit f281233d3e
115 changed files with 347 additions and 199 deletions
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3
drivers/scsi/dc395x.c
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@@ -1080,7 +1080,7 @@ static void build_srb(struct scsi_cmnd *cmd, struct DeviceCtlBlk *dcb,
* and is expected to be held on return.
*
**/
static int dc395x_queue_command(struct scsi_cmnd *cmd, void (*done)(struct scsi_cmnd *))
static int dc395x_queue_command_lck(struct scsi_cmnd *cmd, void (*done)(struct scsi_cmnd *))
{
struct DeviceCtlBlk *dcb;
struct ScsiReqBlk *srb;
@@ -1154,6 +1154,7 @@ complete:
return 0;
}
static DEF_SCSI_QCMD(dc395x_queue_command)
/*
* Return the disk geometry for the given SCSI device.