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>

diff --git a/drivers/net/bnx2x_main.c b/drivers/net/bnx2x_main.c
index a66536ec10a43402cc3af854c5427ba6fb7156fd..e0851a744c421b068174e44224e84a77c53ae796 100644 (file)
--- 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;
 }