//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);	}}