bnx2x: napi_poll budget check

Check the napi_poll budget only when updating it. Also add a comment to explain
the rmb

Signed-off-by: Eilon Greenstein <eilong@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 18 insertions, 4 deletions

diff --git a/drivers/net/bnx2x_main.c b/drivers/net/bnx2x_main.c
index a66536ec10a4..e0851a744c42 100644
--- a/drivers/net/bnx2x_main.c
+++ b/drivers/net/bnx2x_main.c
@@ -10068,14 +10068,27 @@ static int bnx2x_poll(struct napi_struct *napi, int budget)
         if (bnx2x_has_tx_work(fp))
                 bnx2x_tx_int(fp);
 
-        if (bnx2x_has_rx_work(fp))
+        if (bnx2x_has_rx_work(fp)) {
                 work_done = bnx2x_rx_int(fp, budget);
 
-        rmb(); /* BNX2X_HAS_WORK() reads the status block */
+                /* must not complete if we consumed full budget */
+                if (work_done >= budget)
+                        goto poll_again;
+        }
 
-        /* must not complete if we consumed full budget */
-        if ((work_done < budget) && !BNX2X_HAS_WORK(fp)) {
+        /* BNX2X_HAS_WORK() reads the status block, thus we need to
+         * ensure that status block indices have been actually read
+         * (bnx2x_update_fpsb_idx) prior to this check (BNX2X_HAS_WORK)
+         * so that we won't write the "newer" value of the status block to IGU
+         * (if there was a DMA right after BNX2X_HAS_WORK and
+         * if there is no rmb, the memory reading (bnx2x_update_fpsb_idx)
+         * may be postponed to right before bnx2x_ack_sb). In this case
+         * there will never be another interrupt until there is another update
+         * of the status block, while there is still unhandled work.
+         */
+        rmb();
 
+        if (!BNX2X_HAS_WORK(fp)) {
 #ifdef BNX2X_STOP_ON_ERROR
 poll_panic:
 #endif
@@ -10087,6 +10100,7 @@ poll_panic:
                              le16_to_cpu(fp->fp_c_idx), IGU_INT_ENABLE, 1);
         }
 
+poll_again:
         return work_done;
 }