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- // SPDX-License-Identifier: GPL-2.0
- #include <linux/cgroup.h>
- #include <linux/sched.h>
- #include <linux/sched/task.h>
- #include <linux/sched/signal.h>
- #include "cgroup-internal.h"
- #include <trace/events/cgroup.h>
- #include <trace/hooks/dtask.h>
- /*
- * Propagate the cgroup frozen state upwards by the cgroup tree.
- */
- static void cgroup_propagate_frozen(struct cgroup *cgrp, bool frozen)
- {
- int desc = 1;
- /*
- * If the new state is frozen, some freezing ancestor cgroups may change
- * their state too, depending on if all their descendants are frozen.
- *
- * Otherwise, all ancestor cgroups are forced into the non-frozen state.
- */
- while ((cgrp = cgroup_parent(cgrp))) {
- if (frozen) {
- cgrp->freezer.nr_frozen_descendants += desc;
- if (!test_bit(CGRP_FROZEN, &cgrp->flags) &&
- test_bit(CGRP_FREEZE, &cgrp->flags) &&
- cgrp->freezer.nr_frozen_descendants ==
- cgrp->nr_descendants) {
- set_bit(CGRP_FROZEN, &cgrp->flags);
- cgroup_file_notify(&cgrp->events_file);
- TRACE_CGROUP_PATH(notify_frozen, cgrp, 1);
- desc++;
- }
- } else {
- cgrp->freezer.nr_frozen_descendants -= desc;
- if (test_bit(CGRP_FROZEN, &cgrp->flags)) {
- clear_bit(CGRP_FROZEN, &cgrp->flags);
- cgroup_file_notify(&cgrp->events_file);
- TRACE_CGROUP_PATH(notify_frozen, cgrp, 0);
- desc++;
- }
- }
- }
- }
- /*
- * Revisit the cgroup frozen state.
- * Checks if the cgroup is really frozen and perform all state transitions.
- */
- void cgroup_update_frozen(struct cgroup *cgrp)
- {
- bool frozen;
- lockdep_assert_held(&css_set_lock);
- /*
- * If the cgroup has to be frozen (CGRP_FREEZE bit set),
- * and all tasks are frozen and/or stopped, let's consider
- * the cgroup frozen. Otherwise it's not frozen.
- */
- frozen = test_bit(CGRP_FREEZE, &cgrp->flags) &&
- cgrp->freezer.nr_frozen_tasks == __cgroup_task_count(cgrp);
- if (frozen) {
- /* Already there? */
- if (test_bit(CGRP_FROZEN, &cgrp->flags))
- return;
- set_bit(CGRP_FROZEN, &cgrp->flags);
- } else {
- /* Already there? */
- if (!test_bit(CGRP_FROZEN, &cgrp->flags))
- return;
- clear_bit(CGRP_FROZEN, &cgrp->flags);
- }
- cgroup_file_notify(&cgrp->events_file);
- TRACE_CGROUP_PATH(notify_frozen, cgrp, frozen);
- /* Update the state of ancestor cgroups. */
- cgroup_propagate_frozen(cgrp, frozen);
- }
- /*
- * Increment cgroup's nr_frozen_tasks.
- */
- static void cgroup_inc_frozen_cnt(struct cgroup *cgrp)
- {
- cgrp->freezer.nr_frozen_tasks++;
- }
- /*
- * Decrement cgroup's nr_frozen_tasks.
- */
- static void cgroup_dec_frozen_cnt(struct cgroup *cgrp)
- {
- cgrp->freezer.nr_frozen_tasks--;
- WARN_ON_ONCE(cgrp->freezer.nr_frozen_tasks < 0);
- }
- /*
- * Enter frozen/stopped state, if not yet there. Update cgroup's counters,
- * and revisit the state of the cgroup, if necessary.
- */
- void cgroup_enter_frozen(void)
- {
- struct cgroup *cgrp;
- if (current->frozen)
- return;
- spin_lock_irq(&css_set_lock);
- current->frozen = true;
- cgrp = task_dfl_cgroup(current);
- cgroup_inc_frozen_cnt(cgrp);
- cgroup_update_frozen(cgrp);
- spin_unlock_irq(&css_set_lock);
- }
- /*
- * Conditionally leave frozen/stopped state. Update cgroup's counters,
- * and revisit the state of the cgroup, if necessary.
- *
- * If always_leave is not set, and the cgroup is freezing,
- * we're racing with the cgroup freezing. In this case, we don't
- * drop the frozen counter to avoid a transient switch to
- * the unfrozen state.
- */
- void cgroup_leave_frozen(bool always_leave)
- {
- struct cgroup *cgrp;
- spin_lock_irq(&css_set_lock);
- cgrp = task_dfl_cgroup(current);
- if (always_leave || !test_bit(CGRP_FREEZE, &cgrp->flags)) {
- cgroup_dec_frozen_cnt(cgrp);
- cgroup_update_frozen(cgrp);
- WARN_ON_ONCE(!current->frozen);
- current->frozen = false;
- } else if (!(current->jobctl & JOBCTL_TRAP_FREEZE)) {
- spin_lock(¤t->sighand->siglock);
- current->jobctl |= JOBCTL_TRAP_FREEZE;
- set_thread_flag(TIF_SIGPENDING);
- spin_unlock(¤t->sighand->siglock);
- }
- spin_unlock_irq(&css_set_lock);
- }
- /*
- * Freeze or unfreeze the task by setting or clearing the JOBCTL_TRAP_FREEZE
- * jobctl bit.
- */
- static void cgroup_freeze_task(struct task_struct *task, bool freeze)
- {
- unsigned long flags;
- bool wake = true;
- /* If the task is about to die, don't bother with freezing it. */
- if (!lock_task_sighand(task, &flags))
- return;
- trace_android_vh_freeze_whether_wake(task, &wake);
- if (freeze) {
- task->jobctl |= JOBCTL_TRAP_FREEZE;
- if (wake)
- signal_wake_up(task, false);
- } else {
- task->jobctl &= ~JOBCTL_TRAP_FREEZE;
- if (wake)
- wake_up_process(task);
- }
- unlock_task_sighand(task, &flags);
- }
- /*
- * Freeze or unfreeze all tasks in the given cgroup.
- */
- static void cgroup_do_freeze(struct cgroup *cgrp, bool freeze)
- {
- struct css_task_iter it;
- struct task_struct *task;
- lockdep_assert_held(&cgroup_mutex);
- spin_lock_irq(&css_set_lock);
- if (freeze)
- set_bit(CGRP_FREEZE, &cgrp->flags);
- else
- clear_bit(CGRP_FREEZE, &cgrp->flags);
- spin_unlock_irq(&css_set_lock);
- if (freeze)
- TRACE_CGROUP_PATH(freeze, cgrp);
- else
- TRACE_CGROUP_PATH(unfreeze, cgrp);
- css_task_iter_start(&cgrp->self, 0, &it);
- while ((task = css_task_iter_next(&it))) {
- /*
- * Ignore kernel threads here. Freezing cgroups containing
- * kthreads isn't supported.
- */
- if (task->flags & PF_KTHREAD)
- continue;
- cgroup_freeze_task(task, freeze);
- }
- css_task_iter_end(&it);
- /*
- * Cgroup state should be revisited here to cover empty leaf cgroups
- * and cgroups which descendants are already in the desired state.
- */
- spin_lock_irq(&css_set_lock);
- if (cgrp->nr_descendants == cgrp->freezer.nr_frozen_descendants)
- cgroup_update_frozen(cgrp);
- spin_unlock_irq(&css_set_lock);
- }
- /*
- * Adjust the task state (freeze or unfreeze) and revisit the state of
- * source and destination cgroups.
- */
- void cgroup_freezer_migrate_task(struct task_struct *task,
- struct cgroup *src, struct cgroup *dst)
- {
- lockdep_assert_held(&css_set_lock);
- /*
- * Kernel threads are not supposed to be frozen at all.
- */
- if (task->flags & PF_KTHREAD)
- return;
- /*
- * It's not necessary to do changes if both of the src and dst cgroups
- * are not freezing and task is not frozen.
- */
- if (!test_bit(CGRP_FREEZE, &src->flags) &&
- !test_bit(CGRP_FREEZE, &dst->flags) &&
- !task->frozen)
- return;
- /*
- * Adjust counters of freezing and frozen tasks.
- * Note, that if the task is frozen, but the destination cgroup is not
- * frozen, we bump both counters to keep them balanced.
- */
- if (task->frozen) {
- cgroup_inc_frozen_cnt(dst);
- cgroup_dec_frozen_cnt(src);
- }
- cgroup_update_frozen(dst);
- cgroup_update_frozen(src);
- /*
- * Force the task to the desired state.
- */
- cgroup_freeze_task(task, test_bit(CGRP_FREEZE, &dst->flags));
- }
- void cgroup_freeze(struct cgroup *cgrp, bool freeze)
- {
- struct cgroup_subsys_state *css;
- struct cgroup *dsct;
- bool applied = false;
- lockdep_assert_held(&cgroup_mutex);
- /*
- * Nothing changed? Just exit.
- */
- if (cgrp->freezer.freeze == freeze)
- return;
- cgrp->freezer.freeze = freeze;
- /*
- * Propagate changes downwards the cgroup tree.
- */
- css_for_each_descendant_pre(css, &cgrp->self) {
- dsct = css->cgroup;
- if (cgroup_is_dead(dsct))
- continue;
- if (freeze) {
- dsct->freezer.e_freeze++;
- /*
- * Already frozen because of ancestor's settings?
- */
- if (dsct->freezer.e_freeze > 1)
- continue;
- } else {
- dsct->freezer.e_freeze--;
- /*
- * Still frozen because of ancestor's settings?
- */
- if (dsct->freezer.e_freeze > 0)
- continue;
- WARN_ON_ONCE(dsct->freezer.e_freeze < 0);
- }
- /*
- * Do change actual state: freeze or unfreeze.
- */
- cgroup_do_freeze(dsct, freeze);
- applied = true;
- }
- /*
- * Even if the actual state hasn't changed, let's notify a user.
- * The state can be enforced by an ancestor cgroup: the cgroup
- * can already be in the desired state or it can be locked in the
- * opposite state, so that the transition will never happen.
- * In both cases it's better to notify a user, that there is
- * nothing to wait for.
- */
- if (!applied) {
- TRACE_CGROUP_PATH(notify_frozen, cgrp,
- test_bit(CGRP_FROZEN, &cgrp->flags));
- cgroup_file_notify(&cgrp->events_file);
- }
- }
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