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-rw-r--r--kernel/cgroup/freezer.c323
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..3984dd6b8
--- /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(&current->sighand->siglock);
+ current->jobctl |= JOBCTL_TRAP_FREEZE;
+ set_thread_flag(TIF_SIGPENDING);
+ spin_unlock(&current->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);
+ }
+}