[dpdk-stable] [PATCH] [18.11] net/mlx5: use open/read/close for ib stats query

[Kevin Traynor]

On 08/12/2020 11:34, Viacheslav Ovsiienko wrote:
> From: Mohsin Shaikh <mohsinshaikh at niometrics.com>
> 
> From: Mohsin Shaikh <mohsinshaikh at niometrics.com>
> 

Hi Slava, your patches are putting in duplicate From: tags ^ and missing
upstream commit ids. Please add upstream commit ids so I don't have to
find it for every patch. i.e.

[ 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 at dpdk.org
> 

We can drop the stable tag as it's targetted to LTS branch anyway

> Signed-off-by: Mohsin Shaikh <mohsinshaikh at niometrics.com>
> Reviewed-by: Alexander Kozyrev <akozyrev at mellanox.com>
> Acked-by: Viacheslav Ovsiienko <viacheslavo at 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;
>  }
>  
>  /**
>