net/mlx5: use open/read/close for ib stats query

fgets(3)/fread(3)/fscanf(3) etc. use mmap(2)/munmap(2) which leads
to TLB shutdown interrupts to all DPDK app cores including RX cores.
This can cause packet drops. Use read(2)/write(2) instead.

Bugzilla ID: 440
Cc: stable@dpdk.org
Signed-off-by: Mohsin Shaikh <mohsinshaikh@niometrics.com>
Reviewed-by: Alexander Kozyrev <akozyrev@mellanox.com>
Acked-by: Viacheslav Ovsiienko <viacheslavo@mellanox.com>

diff --git a/drivers/net/mlx5/mlx5_stats.c b/drivers/net/mlx5/mlx5_stats.c
index 5bc6fa6..b4ca692 100644 (file)
--- a/drivers/net/mlx5/mlx5_stats.c
+++ b/drivers/net/mlx5/mlx5_stats.c
@@ -3,11 +3,13 @@
  * Copyright 2015 Mellanox Technologies, Ltd
  */
 
+#include <fcntl.h>
 #include <inttypes.h>
 #include <linux/sockios.h>
 #include <linux/ethtool.h>
 #include <stdint.h>
 #include <stdio.h>
+#include <unistd.h>
 
 #include <rte_ethdev_driver.h>
 #include <rte_common.h>
@@ -142,20 +144,23 @@ static const unsigned int xstats_n = RTE_DIM(mlx5_counters_init);
 static inline int
 mlx5_read_ib_stat(struct mlx5_priv *priv, const char *ctr_name, uint64_t *stat)
 {
-       FILE *file;
+       int fd;
+
        if (priv->sh) {
                MKSTR(path, "%s/ports/%d/hw_counters/%s",
                          priv->sh->ibdev_path,
                          priv->ibv_port,
                          ctr_name);
-
-               file = fopen(path, "rb");
-               if (file) {
-                       int n = fscanf(file, "%" SCNu64, stat);
-
-                       fclose(file);
-                       if (n == 1)
+               fd = open(path, O_RDONLY);
+               if (fd != -1) {
+                       char buf[21] = {'\0'};
+                       ssize_t n = read(fd, buf, sizeof(buf));
+
+                       close(fd);
+                       if (n != -1) {
+                               *stat = strtoull(buf, NULL, 10);
                                return 0;
+                       }
                }
        }
        *stat = 0;