bnx2x: avoid soft lockup in bnx2x_poll()

Under heavy TX load, bnx2x_poll() can loop forever and trigger
soft lockup bugs.

A napi poll handler must yield after one TX completion round,
risk of livelock is too high otherwise.

Bug is very easy to trigger using a debug build, and udp flood, because
of added cpu cycles in TX completion, and we do not receive enough
packets to break the loop.

Reported-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Ariel Elior <ariel.elior@qlogic.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/drivers/net/ethernet/broadcom/bnx2x/bnx2x_cmn.c b/drivers/net/ethernet/broadcom/bnx2x/bnx2x_cmn.c
index f6634a524153bf35b0ae1c452c6736d8a03fa3e0..d7cc2aa7c37ae6e905a33c159fde9f1ca42f0ac1 100644 (file)
--- a/drivers/net/ethernet/broadcom/bnx2x/bnx2x_cmn.c
+++ b/drivers/net/ethernet/broadcom/bnx2x/bnx2x_cmn.c
@@ -3204,42 +3204,32 @@ int bnx2x_set_power_state(struct bnx2x *bp, pci_power_t state)
  */
 static int bnx2x_poll(struct napi_struct *napi, int budget)
 {
-       int work_done = 0;
-       u8 cos;
        struct bnx2x_fastpath *fp = container_of(napi, struct bnx2x_fastpath,
                                                 napi);
        struct bnx2x *bp = fp->bp;
+       int rx_work_done;
+       u8 cos;
 
-       while (1) {
 #ifdef BNX2X_STOP_ON_ERROR
-               if (unlikely(bp->panic)) {
-                       napi_complete(napi);
-                       return 0;
-               }
+       if (unlikely(bp->panic)) {
+               napi_complete(napi);
+               return 0;
+       }
 #endif
-               for_each_cos_in_tx_queue(fp, cos)
-                       if (bnx2x_tx_queue_has_work(fp->txdata_ptr[cos]))
-                               bnx2x_tx_int(bp, fp->txdata_ptr[cos]);
-
-               if (bnx2x_has_rx_work(fp)) {
-                       work_done += bnx2x_rx_int(fp, budget - work_done);
-
-                       /* must not complete if we consumed full budget */
-                       if (work_done >= budget)
-                               break;
-               }
+       for_each_cos_in_tx_queue(fp, cos)
+               if (bnx2x_tx_queue_has_work(fp->txdata_ptr[cos]))
+                       bnx2x_tx_int(bp, fp->txdata_ptr[cos]);
 
-               /* Fall out from the NAPI loop if needed */
-               if (!(bnx2x_has_rx_work(fp) || bnx2x_has_tx_work(fp))) {
+       rx_work_done = (bnx2x_has_rx_work(fp)) ? bnx2x_rx_int(fp, budget) : 0;
 
-                       /* No need to update SB for FCoE L2 ring as long as
-                        * it's connected to the default SB and the SB
-                        * has been updated when NAPI was scheduled.
-                        */
-                       if (IS_FCOE_FP(fp)) {
-                               napi_complete(napi);
-                               break;
-                       }
+       if (rx_work_done < budget) {
+               /* No need to update SB for FCoE L2 ring as long as
+                * it's connected to the default SB and the SB
+                * has been updated when NAPI was scheduled.
+                */
+               if (IS_FCOE_FP(fp)) {
+                       napi_complete(napi);
+               } else {
                        bnx2x_update_fpsb_idx(fp);
                        /* bnx2x_has_rx_work() reads the status block,
                         * thus we need to ensure that status block indices
@@ -3264,12 +3254,13 @@ static int bnx2x_poll(struct napi_struct *napi, int budget)
                                bnx2x_ack_sb(bp, fp->igu_sb_id, USTORM_ID,
                                             le16_to_cpu(fp->fp_hc_idx),
                                             IGU_INT_ENABLE, 1);
-                               break;
+                       } else {
+                               rx_work_done = budget;
                        }
                }
        }
 
-       return work_done;
+       return rx_work_done;
 }
 
 /* we split the first BD into headers and data BDs