diff options
Diffstat (limited to '')
| -rw-r--r-- | kernel/cgroup/freezer.c | 323 |
1 files changed, 323 insertions, 0 deletions
diff --git a/kernel/cgroup/freezer.c b/kernel/cgroup/freezer.c new file mode 100644 index 000000000..617861a54 --- /dev/null +++ b/kernel/cgroup/freezer.c @@ -0,0 +1,323 @@ +// 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> + +/* + * 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; + + /* If the task is about to die, don't bother with freezing it. */ + if (!lock_task_sighand(task, &flags)) + return; + + if (freeze) { + task->jobctl |= JOBCTL_TRAP_FREEZE; + signal_wake_up(task, false); + } else { + task->jobctl &= ~JOBCTL_TRAP_FREEZE; + 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); + } +} |