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authorJames Smart <james.smart@emulex.com>2014-05-07 17:16:46 -0400
committerChristoph Hellwig <hch@lst.de>2014-05-19 19:12:25 +0200
commit27f344eb15dd0da80ebec80c7245e8c85043f841 (patch)
tree743db60ac9c0037192f89f75038c21308d9613e1
parenta79b03222712e99e6895c3b86f2ebd772b86bfc1 (diff)
lpfc: Add iotag memory barrier
Add a memory barrier to ensure the valid bit is read before any of the cqe payload is read. This fixes an issue seen on Power where the cqe payload was getting loaded before the valid bit. When this occurred, we saw an iotag out of range error when a command completed, but since the iotag looked invalid the command didn't get completed to scsi core. Later we hit the command timeout, attempted to abort the command, then waited for the aborted command to get returned. Since the adapter already returned the command, we timeout waiting, and end up escalating EEH all the way to host reset. This patch fixes this issue. Signed-off-by: Brian King <brking@linux.vnet.ibm.com> Signed-off-by: James Smart <james.smart@emulex.com> --- lpfc_sli.c | 21 +++++++++++++++++++++ 1 file changed, 21 insertions(+) Signed-off-by: Christoph Hellwig <hch@lst.de>
-rw-r--r--drivers/scsi/lpfc/lpfc_sli.c21
1 files changed, 21 insertions, 0 deletions
diff --git a/drivers/scsi/lpfc/lpfc_sli.c b/drivers/scsi/lpfc/lpfc_sli.c
index 6bb51f8e3c1b..393662c24df5 100644
--- a/drivers/scsi/lpfc/lpfc_sli.c
+++ b/drivers/scsi/lpfc/lpfc_sli.c
@@ -265,6 +265,16 @@ lpfc_sli4_eq_get(struct lpfc_queue *q)
return NULL;
q->hba_index = idx;
+
+ /*
+ * insert barrier for instruction interlock : data from the hardware
+ * must have the valid bit checked before it can be copied and acted
+ * upon. Given what was seen in lpfc_sli4_cq_get() of speculative
+ * instructions allowing action on content before valid bit checked,
+ * add barrier here as well. May not be needed as "content" is a
+ * single 32-bit entity here (vs multi word structure for cq's).
+ */
+ mb();
return eqe;
}
@@ -370,6 +380,17 @@ lpfc_sli4_cq_get(struct lpfc_queue *q)
cqe = q->qe[q->hba_index].cqe;
q->hba_index = idx;
+
+ /*
+ * insert barrier for instruction interlock : data from the hardware
+ * must have the valid bit checked before it can be copied and acted
+ * upon. Speculative instructions were allowing a bcopy at the start
+ * of lpfc_sli4_fp_handle_wcqe(), which is called immediately
+ * after our return, to copy data before the valid bit check above
+ * was done. As such, some of the copied data was stale. The barrier
+ * ensures the check is before any data is copied.
+ */
+ mb();
return cqe;
}