Re: [dpdk-dev] [PATCH v4 2/2] eal/linux: Add support for handling built-in kernel modules

[Panu Matilainen <pmatilai@redhat.com>]

On 12/08/2015 05:33 PM, Kamil Rytarowski wrote:
> Currently rte_eal_check_module() detects Linux kernel modules via reading
> /proc/modules. Built-in ones aren't listed there and therefore they are not
> being found by the script.
>
> Add support for checking built-in modules with parsing the sysfs files
>
> This commit obsoletes the /proc/modules parsing approach.
>
> Signed-off-by: Kamil Rytarowski <Kamil.Rytarowski@caviumnetworks.com>
> Signed-off-by: David Marchand <david.marchand@6wind.com>
> ---
>   lib/librte_eal/linuxapp/eal/eal.c | 34 ++++++++++++++++++++--------------
>   1 file changed, 20 insertions(+), 14 deletions(-)
>
> diff --git a/lib/librte_eal/linuxapp/eal/eal.c b/lib/librte_eal/linuxapp/eal/eal.c
> index 635ec36..92482a0 100644
> --- a/lib/librte_eal/linuxapp/eal/eal.c
> +++ b/lib/librte_eal/linuxapp/eal/eal.c
> @@ -901,27 +901,33 @@ int rte_eal_has_hugepages(void)
>   int
>   rte_eal_check_module(const char *module_name)
>   {
> -	char mod_name[30]; /* Any module names can be longer than 30 bytes? */
> -	int ret = 0;
> +	char sysfs_mod_name[PATH_MAX];
> +	struct stat st;
>   	int n;
>
>   	if (NULL == module_name)
>   		return -1;
>
> -	FILE *fd = fopen("/proc/modules", "r");
> -	if (NULL == fd) {
> -		RTE_LOG(ERR, EAL, "Open /proc/modules failed!"
> -			" error %i (%s)\n", errno, strerror(errno));
> +	/* Check if there is sysfs mounted */
> +	if (stat("/sys/module", &st) != 0) {
> +		RTE_LOG(DEBUG, EAL, "sysfs is not mounted! error %i (%s)\n",
> +			errno, strerror(errno));
>   		return -1;
>   	}
> -	while (!feof(fd)) {
> -		n = fscanf(fd, "%29s %*[^\n]", mod_name);
> -		if ((n == 1) && !strcmp(mod_name, module_name)) {
> -			ret = 1;
> -			break;
> -		}
> +
> +	/* A module might be built-in, therefore try sysfs */
> +	n = snprintf(sysfs_mod_name, PATH_MAX, "/sys/module/%s", module_name);
> +	if (n < 0 || n > PATH_MAX) {
> +		RTE_LOG(DEBUG, EAL, "Could not format module path\n");
> +		return -1;
>   	}
> -	fclose(fd);
>
> -	return ret;
> +	if (stat(sysfs_mod_name, &st) != 0) {
> +		RTE_LOG(DEBUG, EAL, "Open %s failed! error %i (%s)\n",
> +		        sysfs_mod_name, errno, strerror(errno));
> +		return 0;
> +	}

Like with /sys/module, its not trying to *open* sysfs_mod_name directory 
either so it shouldn't claim to do so.

I did use plural on purpose when I said "the debug messages are 
incorrect/misleading. It's certainly not trying to *open* these 
directories so it should not claim to do so" in my previous mail :)

- Panu -