[LTP] [PATCH 1/1] lib/tst_pid.c: Count used pid by traversing /proc

[Cyril Hrubis]

Hi!
> Use "ps -eT | wc -l" to calculate the number of used pid
> could have an incorrectly larger result because "ps -eT"
> may list the same pid multiple times (with different SPID).
> 
> Instead, we could count used pid by traversing /proc
> directory and count the subdirectories that have name
> composed of digits.
> 
> Increase PIDS_RESERVED to avoid fork failure.

The changes looks good, but can we please split the patch into two?

We should keep the change to the PIDS_RESERVED separate from the code
changes.

> Signed-off-by: Leo Yu-Chi Liang <ycliang@andestech.com>
> ---
>  lib/tst_pid.c | 26 +++++++++++---------------
>  1 file changed, 11 insertions(+), 15 deletions(-)
> 
> diff --git a/lib/tst_pid.c b/lib/tst_pid.c
> index 5595e79bd..7582e4828 100644
> --- a/lib/tst_pid.c
> +++ b/lib/tst_pid.c
> @@ -18,6 +18,7 @@
>   *   Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
>   */
>  
> +#include <ctype.h>
>  #include <errno.h>
>  #include <fcntl.h>
>  #include <limits.h>
> @@ -35,7 +36,7 @@
>  #define CGROUPS_V1_SLICE_FMT "/sys/fs/cgroup/pids/user.slice/user-%d.slice/pids.max"
>  #define CGROUPS_V2_SLICE_FMT "/sys/fs/cgroup/user.slice/user-%d.slice/pids.max"
>  /* Leave some available processes for the OS */
> -#define PIDS_RESERVE 50
> +#define PIDS_RESERVE 200
>  
>  pid_t tst_get_unused_pid_(void (*cleanup_fn) (void))
>  {
> @@ -113,21 +114,16 @@ static int get_session_pids_limit(void (*cleanup_fn) (void))
>  
>  int tst_get_free_pids_(void (*cleanup_fn) (void))
>  {
> -	FILE *f;
> -	int rc, used_pids, max_pids, max_session_pids, max_threads;
> -
> -	f = popen("ps -eT | wc -l", "r");
> -	if (!f) {
> -		tst_brkm(TBROK, cleanup_fn, "Could not run 'ps' to calculate used pids");
> -		return -1;
> -	}
> -	rc = fscanf(f, "%i", &used_pids);
> -	pclose(f);
> -
> -	if (rc != 1 || used_pids < 0) {
> -		tst_brkm(TBROK, cleanup_fn, "Could not read output of 'ps' to calculate used pids");
> -		return -1;
> +	DIR *f;
> +	struct dirent *ent;
> +	int max_pids, max_session_pids, max_threads, used_pids = 0;
> +
> +	f = SAFE_OPENDIR("/proc");
> +	while ((ent = SAFE_READDIR(f))) {
> +		if (isdigit(ent->d_name[0]))
> +			++used_pids;
>  	}
> +	SAFE_CLOSEDIR(f);
>  
>  	SAFE_FILE_SCANF(cleanup_fn, PID_MAX_PATH, "%d", &max_pids);
>  	SAFE_FILE_SCANF(cleanup_fn, THREADS_MAX_PATH, "%d", &max_threads);
> -- 
> 2.34.1
> 
> 
> -- 
> Mailing list info: https://lists.linux.it/listinfo/ltp

-- 
Cyril Hrubis
chrubis@suse.cz