Nicky Chorley <ndchorley@xxxxxxxxx>于2022年8月9日 周二20:31写道：
Hi folks,
I wrote a small program to start a new process (a shell), create a
cgroup and add the process to it. This all works fine - the process ID
of the shell ends up in the cgroup.procs file and when my program
exits, cgroup.procs ends up empty as expected. If I try and remove the
cgroup directory, though, I get a load of "Operation not permitted"
errors and I'm not sure why. I'm running on openSUSE (kernel 5.3.18)
with cgroups v2.
My program looks like:
#define _GNU_SOURCE
#include <sched.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/stat.h>
#include <sys/wait.h>
#include <unistd.h>
int startShell(void *argument) {
char* arguments[] = {"bash", NULL};
char* environment[] = {NULL};
execve("/bin/bash", arguments, environment);
return 0;
}
int main() {
mkdir(
"/sys/fs/cgroup/my_group",
S_IRWXO | S_IRGRP | S_IROTH
);
int stackSizeBytes = 65536;
char *stackStart = malloc(stackSizeBytes);
char *stackEnd = stackStart + stackSizeBytes;
pid_t childPid = clone(
startShell,
stackEnd,
SIGCHLD,
NULL
);
FILE* procsFile = fopen(
"/sys/fs/cgroup/my_group/cgroup.procs",
"w"
);
fprintf(procsFile, "%d\n", childPid);
fclose(procsFile);
waitpid(childPid, NULL, 0);
return 0;
}
and output looks like:
$ su -c ./run
Password:
# echo $$
4382
# cat /sys/fs/cgroup/my_group/cgroup.procs
4382
4522
# exit
$ cat /sys/fs/cgroup/my_group/cgroup.procs
$ su -c "rm -rf /sys/fs/cgroup/my_group"
You have to use rmdir to remove
Password:
rm: cannot remove '/sys/fs/cgroup/my_group/cgroup.events': Operation
not permitted
rm: cannot remove '/sys/fs/cgroup/my_group/memory.events': Operation
not permitted
... other lines omitted for brevity
Could someone please help me understand what's going on here?
Thanks!
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