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