examples/l3fwd-power: fix race on interrupt wakeup log

Currently, the interrupt status notification prevents log spam by
remembering whether previous interrupt wakeup was due to traffic or due
to timeout expiring. However, it is a single variable that can
potentially be accessed from multiple threads, so it is not thread-safe.

Fix it by having per-lcore interrupt status.

Fixes: f4d1e19c293d ("examples/l3fwd-power: add Rx interrupt timeout")
Cc: stable@dpdk.org
Signed-off-by: Anatoly Burakov <anatoly.burakov@intel.com>
Acked-by: David Hunt <david.hunt@intel.com>
Tested-by: Xi Zhang <xix.zhang@intel.com>

diff --git a/examples/l3fwd-power/main.c b/examples/l3fwd-power/main.c
index a48d75f..2874285 100644 (file)
--- a/examples/l3fwd-power/main.c
+++ b/examples/l3fwd-power/main.c
@@ -821,20 +821,23 @@ power_freq_scaleup_heuristic(unsigned lcore_id,
  *  0 on success
  */
 static int
-sleep_until_rx_interrupt(int num)
+sleep_until_rx_interrupt(int num, int lcore)
 {
        /*
         * we want to track when we are woken up by traffic so that we can go
-        * back to sleep again without log spamming.
+        * back to sleep again without log spamming. Avoid cache line sharing
+        * to prevent threads stepping on each others' toes.
         */
-       static bool timeout;
+       static struct {
+               bool wakeup;
+       } __rte_cache_aligned status[RTE_MAX_LCORE];
        struct rte_epoll_event event[num];
        int n, i;
        uint16_t port_id;
        uint8_t queue_id;
        void *data;
 
-       if (!timeout) {
+       if (status[lcore].wakeup) {
                RTE_LOG(INFO, L3FWD_POWER,
                                "lcore %u sleeps until interrupt triggers\n",
                                rte_lcore_id());
@@ -851,7 +854,7 @@ sleep_until_rx_interrupt(int num)
                        " port %d queue %d\n",
                        rte_lcore_id(), port_id, queue_id);
        }
-       timeout = n == 0;
+       status[lcore].wakeup = n != 0;
 
        return 0;
 }
@@ -1050,7 +1053,8 @@ start_rx:
                                if (intr_en) {
                                        turn_on_off_intr(qconf, 1);
                                        sleep_until_rx_interrupt(
-                                                       qconf->n_rx_queue);
+                                                       qconf->n_rx_queue,
+                                                       lcore_id);
                                        turn_on_off_intr(qconf, 0);
                                        /**
                                         * start receiving packets immediately
@@ -1473,7 +1477,8 @@ start_rx:
                                if (intr_en) {
                                        turn_on_off_intr(qconf, 1);
                                        sleep_until_rx_interrupt(
-                                               qconf->n_rx_queue);
+                                                       qconf->n_rx_queue,
+                                                       lcore_id);
                                        turn_on_off_intr(qconf, 0);
                                        /**
                                         * start receiving packets immediately