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cgroup v2: Don't require CPU controller for CPU accounting in 4.15+
systemd only uses functions that are as of Linux 4.15+ provided externally to the CPU controller (currently usage_usec), so if we have a new enough kernel, we don't need to set CGROUP_MASK_CPU for CPUAccounting=true as the CPU controller does not need to necessarily be enabled in this case. Part of this patch is modelled on an earlier patch by Ryutaroh Matsumoto (see PR #9665).
This commit is contained in:
Chris Down
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commit
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@ -12,6 +12,7 @@
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#include <sys/stat.h>
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#include <sys/statfs.h>
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#include <sys/types.h>
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#include <sys/utsname.h>
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#include <sys/xattr.h>
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#include <unistd.h>
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@ -2822,3 +2823,54 @@ static const char *cgroup_controller_table[_CGROUP_CONTROLLER_MAX] = {
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};
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DEFINE_STRING_TABLE_LOOKUP(cgroup_controller, CGroupController);
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CGroupMask get_cpu_accounting_mask(void) {
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static CGroupMask needed_mask = (CGroupMask) -1;
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/* On kernel ≥4.15 with unified hierarchy, cpu.stat's usage_usec is
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* provided externally from the CPU controller, which means we don't
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* need to enable the CPU controller just to get metrics. This is good,
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* because enabling the CPU controller comes at a minor performance
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* hit, especially when it's propagated deep into large hierarchies.
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* There's also no separate CPU accounting controller available within
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* a unified hierarchy.
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*
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* This combination of factors results in the desired cgroup mask to
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* enable for CPU accounting varying as follows:
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*
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* ╔═════════════════════╤═════════════════════╗
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* ║ Linux ≥4.15 │ Linux <4.15 ║
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* ╔═══════════════╬═════════════════════╪═════════════════════╣
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* ║ Unified ║ nothing │ CGROUP_MASK_CPU ║
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* ╟───────────────╫─────────────────────┼─────────────────────╢
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* ║ Hybrid/Legacy ║ CGROUP_MASK_CPUACCT │ CGROUP_MASK_CPUACCT ║
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* ╚═══════════════╩═════════════════════╧═════════════════════╝
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*
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* We check kernel version here instead of manually checking whether
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* cpu.stat is present for every cgroup, as that check in itself would
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* already be fairly expensive.
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*
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* Kernels where this patch has been backported will therefore have the
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* CPU controller enabled unnecessarily. This is more expensive than
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* necessary, but harmless. ☺️
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*/
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if (needed_mask == (CGroupMask) -1) {
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if (cg_all_unified()) {
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struct utsname u;
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assert_se(uname(&u) >= 0);
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if (str_verscmp(u.release, "4.15") < 0)
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needed_mask = CGROUP_MASK_CPU;
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else
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needed_mask = 0;
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} else
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needed_mask = CGROUP_MASK_CPUACCT;
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}
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return needed_mask;
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}
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bool cpu_accounting_is_cheap(void) {
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return get_cpu_accounting_mask() == 0;
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}
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@ -69,6 +69,9 @@ static inline CGroupMask CGROUP_MASK_EXTEND_JOINED(CGroupMask mask) {
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return mask;
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}
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CGroupMask get_cpu_accounting_mask(void);
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bool cpu_accounting_is_cheap(void);
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/* Special values for all weight knobs on unified hierarchy */
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#define CGROUP_WEIGHT_INVALID ((uint64_t) -1)
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#define CGROUP_WEIGHT_MIN UINT64_C(1)
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@ -1178,7 +1178,7 @@ CGroupMask cgroup_context_get_mask(CGroupContext *c) {
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/* Figure out which controllers we need, based on the cgroup context object */
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if (c->cpu_accounting)
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mask |= CGROUP_MASK_CPUACCT;
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mask |= get_cpu_accounting_mask();
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if (cgroup_context_has_cpu_weight(c) ||
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cgroup_context_has_cpu_shares(c) ||
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@ -2617,13 +2617,15 @@ static int unit_get_cpu_usage_raw(Unit *u, nsec_t *ret) {
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r = cg_all_unified();
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if (r < 0)
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return r;
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/* Requisite controllers for CPU accounting are not enabled */
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if ((get_cpu_accounting_mask() & ~u->cgroup_realized_mask) != 0)
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return -ENODATA;
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if (r > 0) {
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_cleanup_free_ char *val = NULL;
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uint64_t us;
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if ((u->cgroup_realized_mask & CGROUP_MASK_CPU) == 0)
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return -ENODATA;
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r = cg_get_keyed_attribute("cpu", u->cgroup_path, "cpu.stat", STRV_MAKE("usage_usec"), &val);
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if (r < 0)
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return r;
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@ -2636,9 +2638,6 @@ static int unit_get_cpu_usage_raw(Unit *u, nsec_t *ret) {
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ns = us * NSEC_PER_USEC;
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} else {
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if ((u->cgroup_realized_mask & CGROUP_MASK_CPUACCT) == 0)
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return -ENODATA;
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r = cg_get_attribute("cpuacct", u->cgroup_path, "cpuacct.usage", &v);
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if (r == -ENOENT)
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return -ENODATA;
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@ -603,7 +603,7 @@ int bus_cgroup_set_property(
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flags |= UNIT_PRIVATE;
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if (streq(name, "CPUAccounting"))
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return bus_cgroup_set_boolean(u, name, &c->cpu_accounting, CGROUP_MASK_CPUACCT|CGROUP_MASK_CPU, message, flags, error);
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return bus_cgroup_set_boolean(u, name, &c->cpu_accounting, get_cpu_accounting_mask(), message, flags, error);
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if (streq(name, "CPUWeight"))
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return bus_cgroup_set_cpu_weight(u, name, &c->cpu_weight, message, flags, error);
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@ -2,6 +2,8 @@
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#include <stdio.h>
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#include "cgroup.h"
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#include "cgroup-util.h"
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#include "macro.h"
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#include "manager.h"
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#include "rm-rf.h"
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@ -10,11 +12,27 @@
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#include "tests.h"
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#include "unit.h"
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#define ASSERT_CGROUP_MASK(got, expected) \
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log_cgroup_mask(got, expected); \
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assert_se(got == expected)
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#define ASSERT_CGROUP_MASK_JOINED(got, expected) ASSERT_CGROUP_MASK(got, CGROUP_MASK_EXTEND_JOINED(expected))
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static void log_cgroup_mask(CGroupMask got, CGroupMask expected) {
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_cleanup_free_ char *e_store = NULL, *g_store = NULL;
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assert_se(cg_mask_to_string(expected, &e_store) >= 0);
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log_info("Expected mask: %s\n", e_store);
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assert_se(cg_mask_to_string(got, &g_store) >= 0);
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log_info("Got mask: %s\n", g_store);
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}
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static int test_cgroup_mask(void) {
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_cleanup_(rm_rf_physical_and_freep) char *runtime_dir = NULL;
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_cleanup_(manager_freep) Manager *m = NULL;
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Unit *son, *daughter, *parent, *root, *grandchild, *parent_deep;
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int r;
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CGroupMask cpu_accounting_mask = get_cpu_accounting_mask();
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r = enter_cgroup_subroot();
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if (r == -ENOMEDIUM)
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@ -57,36 +75,36 @@ static int test_cgroup_mask(void) {
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root = UNIT_DEREF(parent->slice);
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/* Verify per-unit cgroups settings. */
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assert_se(unit_get_own_mask(son) == (CGROUP_MASK_CPU | CGROUP_MASK_CPUACCT));
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assert_se(unit_get_own_mask(daughter) == 0);
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assert_se(unit_get_own_mask(grandchild) == 0);
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assert_se(unit_get_own_mask(parent_deep) == CGROUP_MASK_MEMORY);
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assert_se(unit_get_own_mask(parent) == (CGROUP_MASK_IO | CGROUP_MASK_BLKIO));
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assert_se(unit_get_own_mask(root) == 0);
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ASSERT_CGROUP_MASK_JOINED(unit_get_own_mask(son), CGROUP_MASK_CPU);
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ASSERT_CGROUP_MASK_JOINED(unit_get_own_mask(daughter), cpu_accounting_mask);
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ASSERT_CGROUP_MASK_JOINED(unit_get_own_mask(grandchild), 0);
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ASSERT_CGROUP_MASK_JOINED(unit_get_own_mask(parent_deep), CGROUP_MASK_MEMORY);
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ASSERT_CGROUP_MASK_JOINED(unit_get_own_mask(parent), (CGROUP_MASK_IO | CGROUP_MASK_BLKIO));
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ASSERT_CGROUP_MASK_JOINED(unit_get_own_mask(root), 0);
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/* Verify aggregation of member masks */
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assert_se(unit_get_members_mask(son) == 0);
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assert_se(unit_get_members_mask(daughter) == 0);
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assert_se(unit_get_members_mask(grandchild) == 0);
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assert_se(unit_get_members_mask(parent_deep) == 0);
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assert_se(unit_get_members_mask(parent) == (CGROUP_MASK_CPU | CGROUP_MASK_CPUACCT | CGROUP_MASK_MEMORY));
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assert_se(unit_get_members_mask(root) == (CGROUP_MASK_CPU | CGROUP_MASK_CPUACCT | CGROUP_MASK_IO | CGROUP_MASK_BLKIO | CGROUP_MASK_MEMORY));
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ASSERT_CGROUP_MASK_JOINED(unit_get_members_mask(son), 0);
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ASSERT_CGROUP_MASK_JOINED(unit_get_members_mask(daughter), 0);
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ASSERT_CGROUP_MASK_JOINED(unit_get_members_mask(grandchild), 0);
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ASSERT_CGROUP_MASK_JOINED(unit_get_members_mask(parent_deep), 0);
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ASSERT_CGROUP_MASK_JOINED(unit_get_members_mask(parent), (CGROUP_MASK_CPU | cpu_accounting_mask | CGROUP_MASK_MEMORY));
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ASSERT_CGROUP_MASK_JOINED(unit_get_members_mask(root), (CGROUP_MASK_CPU | cpu_accounting_mask | CGROUP_MASK_IO | CGROUP_MASK_BLKIO | CGROUP_MASK_MEMORY));
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/* Verify aggregation of sibling masks. */
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assert_se(unit_get_siblings_mask(son) == (CGROUP_MASK_CPU | CGROUP_MASK_CPUACCT | CGROUP_MASK_MEMORY));
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assert_se(unit_get_siblings_mask(daughter) == (CGROUP_MASK_CPU | CGROUP_MASK_CPUACCT | CGROUP_MASK_MEMORY));
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assert_se(unit_get_siblings_mask(grandchild) == 0);
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assert_se(unit_get_siblings_mask(parent_deep) == (CGROUP_MASK_CPU | CGROUP_MASK_CPUACCT | CGROUP_MASK_MEMORY));
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assert_se(unit_get_siblings_mask(parent) == (CGROUP_MASK_CPU | CGROUP_MASK_CPUACCT | CGROUP_MASK_IO | CGROUP_MASK_BLKIO | CGROUP_MASK_MEMORY));
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assert_se(unit_get_siblings_mask(root) == (CGROUP_MASK_CPU | CGROUP_MASK_CPUACCT | CGROUP_MASK_IO | CGROUP_MASK_BLKIO | CGROUP_MASK_MEMORY));
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ASSERT_CGROUP_MASK_JOINED(unit_get_siblings_mask(son), (CGROUP_MASK_CPU | cpu_accounting_mask | CGROUP_MASK_MEMORY));
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ASSERT_CGROUP_MASK_JOINED(unit_get_siblings_mask(daughter), (CGROUP_MASK_CPU | cpu_accounting_mask | CGROUP_MASK_MEMORY));
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ASSERT_CGROUP_MASK_JOINED(unit_get_siblings_mask(grandchild), 0);
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ASSERT_CGROUP_MASK_JOINED(unit_get_siblings_mask(parent_deep), (CGROUP_MASK_CPU | cpu_accounting_mask | CGROUP_MASK_MEMORY));
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ASSERT_CGROUP_MASK_JOINED(unit_get_siblings_mask(parent), (CGROUP_MASK_CPU | cpu_accounting_mask | CGROUP_MASK_IO | CGROUP_MASK_BLKIO | CGROUP_MASK_MEMORY));
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ASSERT_CGROUP_MASK_JOINED(unit_get_siblings_mask(root), (CGROUP_MASK_CPU | cpu_accounting_mask | CGROUP_MASK_IO | CGROUP_MASK_BLKIO | CGROUP_MASK_MEMORY));
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/* Verify aggregation of target masks. */
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assert_se(unit_get_target_mask(son) == ((CGROUP_MASK_CPU | CGROUP_MASK_CPUACCT | CGROUP_MASK_MEMORY) & m->cgroup_supported));
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assert_se(unit_get_target_mask(daughter) == ((CGROUP_MASK_CPU | CGROUP_MASK_CPUACCT | CGROUP_MASK_MEMORY) & m->cgroup_supported));
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assert_se(unit_get_target_mask(grandchild) == 0);
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assert_se(unit_get_target_mask(parent_deep) == ((CGROUP_MASK_CPU | CGROUP_MASK_CPUACCT | CGROUP_MASK_MEMORY) & m->cgroup_supported));
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assert_se(unit_get_target_mask(parent) == ((CGROUP_MASK_CPU | CGROUP_MASK_CPUACCT | CGROUP_MASK_IO | CGROUP_MASK_BLKIO | CGROUP_MASK_MEMORY) & m->cgroup_supported));
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assert_se(unit_get_target_mask(root) == ((CGROUP_MASK_CPU | CGROUP_MASK_CPUACCT | CGROUP_MASK_IO | CGROUP_MASK_BLKIO | CGROUP_MASK_MEMORY) & m->cgroup_supported));
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ASSERT_CGROUP_MASK(unit_get_target_mask(son), (CGROUP_MASK_EXTEND_JOINED(CGROUP_MASK_CPU | cpu_accounting_mask | CGROUP_MASK_MEMORY) & m->cgroup_supported));
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ASSERT_CGROUP_MASK(unit_get_target_mask(daughter), (CGROUP_MASK_EXTEND_JOINED(CGROUP_MASK_CPU | cpu_accounting_mask | CGROUP_MASK_MEMORY) & m->cgroup_supported));
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ASSERT_CGROUP_MASK(unit_get_target_mask(grandchild), 0);
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ASSERT_CGROUP_MASK(unit_get_target_mask(parent_deep), (CGROUP_MASK_EXTEND_JOINED(CGROUP_MASK_CPU | cpu_accounting_mask | CGROUP_MASK_MEMORY) & m->cgroup_supported));
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ASSERT_CGROUP_MASK(unit_get_target_mask(parent), (CGROUP_MASK_EXTEND_JOINED(CGROUP_MASK_CPU | cpu_accounting_mask | CGROUP_MASK_IO | CGROUP_MASK_BLKIO | CGROUP_MASK_MEMORY) & m->cgroup_supported));
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ASSERT_CGROUP_MASK(unit_get_target_mask(root), (CGROUP_MASK_EXTEND_JOINED(CGROUP_MASK_CPU | cpu_accounting_mask | CGROUP_MASK_IO | CGROUP_MASK_BLKIO | CGROUP_MASK_MEMORY) & m->cgroup_supported));
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return 0;
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}
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@ -5,3 +5,4 @@ Description=Daughter Service
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Slice=parent.slice
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Type=oneshot
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ExecStart=/bin/true
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CPUAccounting=true
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