[Xen-devel] [PATCH 3/4] net: Always poll at least one device in net_rx_action

[Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>]

We should only perform the softnet_break check after we have polled
at least one device in net_rx_action.  Otherwise a zero or negative
setting of netdev_budget can lock up the whole system.

Signed-off-by: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>
---

 net/core/dev.c |    7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/net/core/dev.c b/net/core/dev.c
index 4a9c424..22b0fb2 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -4634,16 +4634,15 @@ static void net_rx_action(struct softirq_action *h)
        while (!list_empty(&list)) {
                struct napi_struct *n;
 
+               n = list_first_entry(&list, struct napi_struct, poll_list);
+               budget -= napi_poll(n, &repoll);
+
                /* If softirq window is exhausted then punt.
                 * Allow this to run for 2 jiffies since which will allow
                 * an average latency of 1.5/HZ.
                 */
                if (unlikely(budget <= 0 || time_after_eq(jiffies, time_limit)))
                        goto softnet_break;
-
-
-               n = list_first_entry(&list, struct napi_struct, poll_list);
-               budget -= napi_poll(n, &repoll);
        }
 
        if (!sd_has_rps_ipi_waiting(sd) &&

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