[SCSI] ipr: Remove unnecessary memory barriers (a5fb407e) · Commits · 戴 / test

The ipr driver added some memory barriers in order to ensure a PowerPC sync instruction was executed prior to sending a command to the adapter to ensure the command block was coherent with respect to the PCI bus's view of memory. However, some time ago, the powerpc architecture writel macros were changed to include the sync since most drivers don't properly handle this. So remove these memory barriers since they are not needed and result in executing twice as many sync instructions, which has a significant performance penalty. Signed-off-by:

Brian King <brking@linux.vnet.ibm.com> Signed-off-by:

James Bottomley <JBottomley@Parallels.com>

drivers/scsi/ipr.c

+4 −12

Original line number	Diff line number	Diff line
		@@ -850,8 +850,6 @@ static void ipr_do_req(struct ipr_cmnd *ipr_cmd,

		ipr_trc_hook(ipr_cmd, IPR_TRACE_START, 0);

		mb();

		ipr_send_command(ipr_cmd);
		}

		@@ -985,8 +983,6 @@ static void ipr_send_hcam(struct ipr_ioa_cfg *ioa_cfg, u8 type,

		ipr_trc_hook(ipr_cmd, IPR_TRACE_START, IPR_IOA_RES_ADDR);

		mb();

		ipr_send_command(ipr_cmd);
		} else {
		list_add_tail(&hostrcb->queue, &ioa_cfg->hostrcb_free_q);
		@@ -5863,14 +5859,12 @@ static int ipr_queuecommand_lck(struct scsi_cmnd *scsi_cmd,
		rc = ipr_build_ioadl(ioa_cfg, ipr_cmd);
		}

		if (likely(rc == 0)) {
		mb();
		ipr_send_command(ipr_cmd);
		} else {
		if (unlikely(rc != 0)) {
		list_move_tail(&ipr_cmd->queue, &ioa_cfg->free_q);
		return SCSI_MLQUEUE_HOST_BUSY;
		}

		ipr_send_command(ipr_cmd);
		return 0;
		}

		@@ -6248,8 +6242,6 @@ static unsigned int ipr_qc_issue(struct ata_queued_cmd *qc)
		return AC_ERR_INVALID;
		}

		mb();

		ipr_send_command(ipr_cmd);

		return 0;

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