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cgroup-util: drop handcrafted cg_is_empty(), always check cgroup.events populated field

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This effectively renames cg_is_empty_recursive() to cg_is_empty().
Note that all existing code calls the former and not the latter,
hence with cgv1 support being dropped it's trivial to consult
cgroup.events directly for populated state everywhere.

Additionally, use more generic cg_get_keyed_attribute() helper
rather than cg_read_event().
This commit is contained in:
Mike Yuan
2025-05-26 22:27:26 +02:00
parent 879952a853
commit c3f900770d
8 changed files with 16 additions and 75 deletions
Download Patch File Download Diff File Expand all files Collapse all files

76
src/basic/cgroup-util.c
View File

@@ -792,81 +792,25 @@ int cg_pidref_get_path(const char *controller, const PidRef *pidref, char **ret_
}
int cg_is_empty(const char *controller, const char *path) {
_cleanup_fclose_ FILE *f = NULL;
pid_t pid;
_cleanup_free_ char *t = NULL;
int r;
/* Check if the cgroup hierarchy under 'path' is empty. On cgroup v2 it's exposed via the "populated"
* attribute of "cgroup.events". */
assert(path);
r = cg_enumerate_processes(controller, path, &f);
/* The root cgroup is always populated */
if (empty_or_root(path))
return false;
r = cg_get_keyed_attribute(SYSTEMD_CGROUP_CONTROLLER, path, "cgroup.events", STRV_MAKE("populated"), &t);
if (r == -ENOENT)
return true;
if (r < 0)
return r;
r = cg_read_pid(f, &pid, CGROUP_DONT_SKIP_UNMAPPED);
if (r < 0)
return r;
return r == 0;
}
int cg_is_empty_recursive(const char *controller, const char *path) {
int r;
assert(path);
/* The root cgroup is always populated */
if (controller && empty_or_root(path))
return false;
r = cg_unified_controller(controller);
if (r < 0)
return r;
if (r > 0) {
_cleanup_free_ char *t = NULL;
/* On the unified hierarchy we can check empty state
* via the "populated" attribute of "cgroup.events". */
r = cg_read_event(controller, path, "populated", &t);
if (r == -ENOENT)
return true;
if (r < 0)
return r;
return streq(t, "0");
} else {
_cleanup_closedir_ DIR *d = NULL;
char *fn;
r = cg_is_empty(controller, path);
if (r <= 0)
return r;
r = cg_enumerate_subgroups(controller, path, &d);
if (r == -ENOENT)
return true;
if (r < 0)
return r;
while ((r = cg_read_subgroup(d, &fn)) > 0) {
_cleanup_free_ char *p = NULL;
p = path_join(path, fn);
free(fn);
if (!p)
return -ENOMEM;
r = cg_is_empty_recursive(controller, p);
if (r <= 0)
return r;
}
if (r < 0)
return r;
return true;
}
return streq(t, "0");
}
int cg_split_spec(const char *spec, char **ret_controller, char **ret_path) {

1
src/basic/cgroup-util.h
View File

@@ -233,7 +233,6 @@ int cg_get_xattr_bool(const char *path, const char *name);
int cg_remove_xattr(const char *path, const char *name);
int cg_is_empty(const char *controller, const char *path);
int cg_is_empty_recursive(const char *controller, const char *path);
int cg_get_root_path(char **path);

2
src/core/cgroup.c
View File

@@ -2760,7 +2760,7 @@ int unit_cgroup_is_empty(Unit *u) {
if (!crt->cgroup_path)
return -EOWNERDEAD;
r = cg_is_empty_recursive(SYSTEMD_CGROUP_CONTROLLER, crt->cgroup_path);
r = cg_is_empty(SYSTEMD_CGROUP_CONTROLLER, crt->cgroup_path);
if (r < 0)
log_unit_debug_errno(u, r, "Failed to determine whether cgroup %s is empty: %m", empty_to_root(crt->cgroup_path));
return r;

2
src/core/service.c
View File

@@ -1976,7 +1976,7 @@ static int cgroup_good(Service *s) {
if (!s->cgroup_runtime || !s->cgroup_runtime->cgroup_path)
return 0;
r = cg_is_empty_recursive(SYSTEMD_CGROUP_CONTROLLER, s->cgroup_runtime->cgroup_path);
r = cg_is_empty(SYSTEMD_CGROUP_CONTROLLER, s->cgroup_runtime->cgroup_path);
if (r < 0)
return r;

2
src/login/loginctl.c
View File

@@ -457,7 +457,7 @@ static int show_unit_cgroup(
/* Fallback for older systemd versions where the GetUnitProcesses() call is not yet available */
if (cg_is_empty_recursive(SYSTEMD_CGROUP_CONTROLLER, cgroup) != 0 && leader <= 0)
if (cg_is_empty(SYSTEMD_CGROUP_CONTROLLER, cgroup) != 0 && leader <= 0)
return 0;
show_cgroup_and_extra(SYSTEMD_CGROUP_CONTROLLER, cgroup, prefix, c, &leader, leader > 0, get_output_flags());

2
src/machine/machinectl.c
View File

@@ -436,7 +436,7 @@ static int show_unit_cgroup(sd_bus *bus, const char *unit, pid_t leader) {
/* Fallback for older systemd versions where the GetUnitProcesses() call is not yet available */
if (cg_is_empty_recursive(SYSTEMD_CGROUP_CONTROLLER, cgroup) != 0 && leader <= 0)
if (cg_is_empty(SYSTEMD_CGROUP_CONTROLLER, cgroup) != 0 && leader <= 0)
return 0;
show_cgroup_and_extra(SYSTEMD_CGROUP_CONTROLLER, cgroup, "\t\t ", c, &leader, leader > 0, get_output_flags());

2
src/shared/cgroup-show.c
View File

@@ -251,7 +251,7 @@ int show_cgroup_by_path(
if (!k)
return -ENOMEM;
if (!(flags & OUTPUT_SHOW_ALL) && cg_is_empty_recursive(NULL, k) > 0)
if (!(flags & OUTPUT_SHOW_ALL) && cg_is_empty(NULL, k) > 0)
continue;
if (!shown_pids) {

4
src/test/test-cgroup.c
View File

@@ -106,9 +106,7 @@ TEST(cg_create) {
free(path);
ASSERT_OK_POSITIVE(cg_is_empty(SYSTEMD_CGROUP_CONTROLLER, test_a));
ASSERT_OK_POSITIVE(cg_is_empty(SYSTEMD_CGROUP_CONTROLLER, test_b));
ASSERT_OK_POSITIVE(cg_is_empty_recursive(SYSTEMD_CGROUP_CONTROLLER, test_a));
ASSERT_OK_ZERO(cg_is_empty_recursive(SYSTEMD_CGROUP_CONTROLLER, test_b));
ASSERT_OK_ZERO(cg_is_empty(SYSTEMD_CGROUP_CONTROLLER, test_b));
ASSERT_OK_ZERO(cg_kill_recursive(test_a, 0, 0, NULL, NULL, NULL));
ASSERT_OK_POSITIVE(cg_kill_recursive(test_b, 0, 0, NULL, NULL, NULL));