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

[Leo Liang]

Hi Cyril,

On Tue, Feb 14, 2023 at 11:58:21AM +0100, Cyril Hrubis wrote:
> 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.
> 

Got it!
Will send a v3 ASAP!

Best regards,
Leo

> > 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