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From: Viacheslav Ovsiienko <viacheslavo@nvidia.com>
To: stable@dpdk.org
Cc: ktraynor@redhat.com, mohsinshaikh@niometrics.com
Date: Tue,  8 Dec 2020 12:45:44 +0000
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Subject: [dpdk-stable] [PATCH v2] [18.11] net/mlx5: use open/read/close for
	ib stats query
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From: Mohsin Shaikh <mohsinshaikh@niometrics.com>

[ upstream commit 00437823cb80b8fa87dbe61becc07bd42ee98549 ]

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>
---
 drivers/net/mlx5/mlx5_stats.c | 21 ++++++++++++++-------
 1 file changed, 14 insertions(+), 7 deletions(-)

diff --git a/drivers/net/mlx5/mlx5_stats.c b/drivers/net/mlx5/mlx5_stats.c
index 6906dc8..0b1fe3d 100644
--- 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>
@@ -139,19 +141,24 @@
 static inline void
 mlx5_read_ib_stat(struct mlx5_priv *priv, const char *ctr_name, uint64_t *stat)
 {
-	FILE *file;
+	int fd;
+
 	MKSTR(path, "%s/ports/1/hw_counters/%s",
 		  priv->ibdev_path,
 		  ctr_name);
 
-	file = fopen(path, "rb");
-	if (file) {
-		int n = fscanf(file, "%" SCNu64, stat);
+	fd = open(path, O_RDONLY);
+	if (fd != -1) {
+		char buf[21] = {'\0'};
+		ssize_t n = read(fd, buf, sizeof(buf));
 
-		fclose(file);
-		if (n != 1)
-			stat = 0;
+		close(fd);
+		if (n != -1) {
+			*stat = strtoull(buf, NULL, 10);
+			return;
+		}
 	}
+	*stat = 0;
 }
 
 /**
-- 
1.8.3.1