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, 14 insertions, 0 deletions

diff --git a/drivers/scsi/lpfc/lpfc_nvmet.h b/drivers/scsi/lpfc/lpfc_nvmet.h
index e675ef17be08..88cd62a11c33 100644
--- a/drivers/scsi/lpfc/lpfc_nvmet.h
+++ b/drivers/scsi/lpfc/lpfc_nvmet.h
@@ -73,6 +73,19 @@ struct lpfc_nvmet_tgtport {
 	atomic_t xmt_abort_rsp_error;
 };
 
+struct lpfc_nvmet_ctx_info {
+	struct list_head nvmet_ctx_list;
+	spinlock_t	nvmet_ctx_list_lock; /* lock per CPU */
+	struct lpfc_nvmet_ctx_info *nvmet_ctx_next_cpu;
+	struct lpfc_nvmet_ctx_info *nvmet_ctx_start_cpu;
+	uint16_t	nvmet_ctx_list_cnt;
+	char pad[16];  /* pad to a cache-line */
+};
+
+/* This retrieves the context info associated with the specified cpu / mrq */
+#define lpfc_get_ctx_list(phba, cpu, mrq)  \
+	(phba->sli4_hba.nvmet_ctx_info + ((cpu * phba->cfg_nvmet_mrq) + mrq))
+
 struct lpfc_nvmet_rcv_ctx {
 	union {
 		struct nvmefc_tgt_ls_req ls_req;
@@ -91,6 +104,7 @@ struct lpfc_nvmet_rcv_ctx {
 	uint16_t size;
 	uint16_t entry_cnt;
 	uint16_t cpu;
+	uint16_t idx;
 	uint16_t state;
 	/* States */
 #define LPFC_NVMET_STE_LS_RCV		1