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authorJeff Garzik <jeff@garzik.org>2010-11-16 10:10:29 +0300
committerLinus Torvalds <torvalds@linux-foundation.org>2010-11-17 00:33:23 +0300
commitf281233d3eba15fb225d21ae2e228fd4553d824a (patch)
tree51134454ba8acb558735f90be5540f7d756483e3 /drivers/scsi/scsi.c
parentbdbd01ac444bffb3c9aefed3059d12554059b320 (diff)
downloadlinux-f281233d3eba15fb225d21ae2e228fd4553d824a.tar.xz
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. 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>
Diffstat (limited to 'drivers/scsi/scsi.c')
-rw-r--r--drivers/scsi/scsi.c18
1 files changed, 5 insertions, 13 deletions
diff --git a/drivers/scsi/scsi.c b/drivers/scsi/scsi.c
index 348fba0a8976..2aeb2e9c4d3b 100644
--- a/drivers/scsi/scsi.c
+++ b/drivers/scsi/scsi.c
@@ -634,12 +634,13 @@ void scsi_log_completion(struct scsi_cmnd *cmd, int disposition)
* Description: a serial number identifies a request for error recovery
* and debugging purposes. Protected by the Host_Lock of host.
*/
-static inline void scsi_cmd_get_serial(struct Scsi_Host *host, struct scsi_cmnd *cmd)
+void scsi_cmd_get_serial(struct Scsi_Host *host, struct scsi_cmnd *cmd)
{
cmd->serial_number = host->cmd_serial_number++;
if (cmd->serial_number == 0)
cmd->serial_number = host->cmd_serial_number++;
}
+EXPORT_SYMBOL(scsi_cmd_get_serial);
/**
* scsi_dispatch_command - Dispatch a command to the low-level driver.
@@ -651,7 +652,6 @@ static inline void scsi_cmd_get_serial(struct Scsi_Host *host, struct scsi_cmnd
int scsi_dispatch_cmd(struct scsi_cmnd *cmd)
{
struct Scsi_Host *host = cmd->device->host;
- unsigned long flags = 0;
unsigned long timeout;
int rtn = 0;
@@ -737,23 +737,15 @@ int scsi_dispatch_cmd(struct scsi_cmnd *cmd)
goto out;
}
- spin_lock_irqsave(host->host_lock, flags);
- /*
- * AK: unlikely race here: for some reason the timer could
- * expire before the serial number is set up below.
- *
- * TODO: kill serial or move to blk layer
- */
- scsi_cmd_get_serial(host, cmd);
-
if (unlikely(host->shost_state == SHOST_DEL)) {
cmd->result = (DID_NO_CONNECT << 16);
scsi_done(cmd);
} else {
trace_scsi_dispatch_cmd_start(cmd);
- rtn = host->hostt->queuecommand(cmd, scsi_done);
+ cmd->scsi_done = scsi_done;
+ rtn = host->hostt->queuecommand(host, cmd);
}
- spin_unlock_irqrestore(host->host_lock, flags);
+
if (rtn) {
trace_scsi_dispatch_cmd_error(cmd, rtn);
if (rtn != SCSI_MLQUEUE_DEVICE_BUSY &&