scsi: lpfc: Fix MRQ > 1 context list handling

Various oops including cpu LOCKUPs were seen.

For asynchronously received ius where the driver must assign exchange
resources, the resources were on a single get (free) list and put list
(finished, waiting to be put on get list). As all cpus are sharing the
lists, an interrupt for a receive frame may have to wait for all the
other cpus to place their done work onto the put list before it can
acquire the lock to pull from the list.

Fix by breaking the resource lists into per-cpu lists or at least more
than 1 list with cpu's sharing the lists). A cpu would allocate from the
free list for its own cpu, and put its done work on the its own put list
- avoiding the contention. As cpu load may vary, when empty, a cpu may
grab from another cpu, thereby changing resource distribution.  But
searching for a resource only occurs on 1 or a few cpus until a single
resource can be allocated. if the condition reoccurs, it starts looking
at a different cpu.

Signed-off-by: Dick Kennedy <dick.kennedy@broadcom.com>
Signed-off-by: James Smart <james.smart@broadcom.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

1 files changed, 4 insertions, 7 deletions

diff --git a/drivers/scsi/lpfc/lpfc_attr.c b/drivers/scsi/lpfc/lpfc_attr.c
index 4ed48ed38e79..d3d01ff44423 100644
--- a/drivers/scsi/lpfc/lpfc_attr.c
+++ b/drivers/scsi/lpfc/lpfc_attr.c
@@ -245,13 +245,10 @@ lpfc_nvme_info_show(struct device *dev, struct device_attribute *attr,
 				atomic_read(&tgtp->xmt_abort_rsp),
 				atomic_read(&tgtp->xmt_abort_rsp_error));
 
-		spin_lock(&phba->sli4_hba.nvmet_ctx_get_lock);
-		spin_lock(&phba->sli4_hba.nvmet_ctx_put_lock);
-		tot = phba->sli4_hba.nvmet_xri_cnt -
-			(phba->sli4_hba.nvmet_ctx_get_cnt +
-			phba->sli4_hba.nvmet_ctx_put_cnt);
-		spin_unlock(&phba->sli4_hba.nvmet_ctx_put_lock);
-		spin_unlock(&phba->sli4_hba.nvmet_ctx_get_lock);
+		/* Calculate outstanding IOs */
+		tot = atomic_read(&tgtp->rcv_fcp_cmd_drop);
+		tot += atomic_read(&tgtp->xmt_fcp_release);
+		tot = atomic_read(&tgtp->rcv_fcp_cmd_in) - tot;
 
 		len += snprintf(buf + len, PAGE_SIZE - len,
 				"IO_CTX: %08x  WAIT: cur %08x tot %08x\n"