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32 results

cpuset.c

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  • cpuset.c 75.74 KiB
    /*
     *  kernel/cpuset.c
     *
     *  Processor and Memory placement constraints for sets of tasks.
     *
     *  Copyright (C) 2003 BULL SA.
     *  Copyright (C) 2004-2007 Silicon Graphics, Inc.
     *  Copyright (C) 2006 Google, Inc
     *
     *  Portions derived from Patrick Mochel's sysfs code.
     *  sysfs is Copyright (c) 2001-3 Patrick Mochel
     *
     *  2003-10-10 Written by Simon Derr.
     *  2003-10-22 Updates by Stephen Hemminger.
     *  2004 May-July Rework by Paul Jackson.
     *  2006 Rework by Paul Menage to use generic cgroups
     *  2008 Rework of the scheduler domains and CPU hotplug handling
     *       by Max Krasnyansky
     *
     *  This file is subject to the terms and conditions of the GNU General Public
     *  License.  See the file COPYING in the main directory of the Linux
     *  distribution for more details.
     */
    
    #include <linux/cpu.h>
    #include <linux/cpumask.h>
    #include <linux/cpuset.h>
    #include <linux/err.h>
    #include <linux/errno.h>
    #include <linux/file.h>
    #include <linux/fs.h>
    #include <linux/init.h>
    #include <linux/interrupt.h>
    #include <linux/kernel.h>
    #include <linux/kmod.h>
    #include <linux/list.h>
    #include <linux/mempolicy.h>
    #include <linux/mm.h>
    #include <linux/memory.h>
    #include <linux/export.h>
    #include <linux/mount.h>
    #include <linux/namei.h>
    #include <linux/pagemap.h>
    #include <linux/proc_fs.h>
    #include <linux/rcupdate.h>
    #include <linux/sched.h>
    #include <linux/seq_file.h>
    #include <linux/security.h>
    #include <linux/slab.h>
    #include <linux/spinlock.h>
    #include <linux/stat.h>
    #include <linux/string.h>
    #include <linux/time.h>
    #include <linux/time64.h>
    #include <linux/backing-dev.h>
    #include <linux/sort.h>
    
    #include <asm/uaccess.h>
    #include <linux/atomic.h>
    #include <linux/mutex.h>
    #include <linux/cgroup.h>
    #include <linux/wait.h>
    
    DEFINE_STATIC_KEY_FALSE(cpusets_enabled_key);
    
    /* See "Frequency meter" comments, below. */
    
    struct fmeter {
    	int cnt;		/* unprocessed events count */
    	int val;		/* most recent output value */
    	time64_t time;		/* clock (secs) when val computed */
    	spinlock_t lock;	/* guards read or write of above */
    };
    
    struct cpuset {
    	struct cgroup_subsys_state css;
    
    	unsigned long flags;		/* "unsigned long" so bitops work */
    
    	/*
    	 * On default hierarchy:
    	 *
    	 * The user-configured masks can only be changed by writing to
    	 * cpuset.cpus and cpuset.mems, and won't be limited by the
    	 * parent masks.
    	 *
    	 * The effective masks is the real masks that apply to the tasks
    	 * in the cpuset. They may be changed if the configured masks are
    	 * changed or hotplug happens.
    	 *
    	 * effective_mask == configured_mask & parent's effective_mask,
    	 * and if it ends up empty, it will inherit the parent's mask.
    	 *
    	 *
    	 * On legacy hierachy:
    	 *
    	 * The user-configured masks are always the same with effective masks.
    	 */
    
    	/* user-configured CPUs and Memory Nodes allow to tasks */
    	cpumask_var_t cpus_allowed;
    	nodemask_t mems_allowed;
    
    	/* effective CPUs and Memory Nodes allow to tasks */
    	cpumask_var_t effective_cpus;
    	nodemask_t effective_mems;
    
    	/*
    	 * This is old Memory Nodes tasks took on.
    	 *
    	 * - top_cpuset.old_mems_allowed is initialized to mems_allowed.
    	 * - A new cpuset's old_mems_allowed is initialized when some
    	 *   task is moved into it.
    	 * - old_mems_allowed is used in cpuset_migrate_mm() when we change
    	 *   cpuset.mems_allowed and have tasks' nodemask updated, and
    	 *   then old_mems_allowed is updated to mems_allowed.
    	 */
    	nodemask_t old_mems_allowed;
    
    	struct fmeter fmeter;		/* memory_pressure filter */
    
    	/*
    	 * Tasks are being attached to this cpuset.  Used to prevent
    	 * zeroing cpus/mems_allowed between ->can_attach() and ->attach().
    	 */
    	int attach_in_progress;
    
    	/* partition number for rebuild_sched_domains() */
    	int pn;
    
    	/* for custom sched domain */
    	int relax_domain_level;
    };
    
    static inline struct cpuset *css_cs(struct cgroup_subsys_state *css)
    {
    	return css ? container_of(css, struct cpuset, css) : NULL;
    }
    
    /* Retrieve the cpuset for a task */
    static inline struct cpuset *task_cs(struct task_struct *task)
    {
    	return css_cs(task_css(task, cpuset_cgrp_id));
    }
    
    static inline struct cpuset *parent_cs(struct cpuset *cs)
    {
    	return css_cs(cs->css.parent);
    }
    
    #ifdef CONFIG_NUMA
    static inline bool task_has_mempolicy(struct task_struct *task)
    {
    	return task->mempolicy;
    }
    #else
    static inline bool task_has_mempolicy(struct task_struct *task)
    {
    	return false;
    }
    #endif
    
    
    /* bits in struct cpuset flags field */
    typedef enum {
    	CS_ONLINE,
    	CS_CPU_EXCLUSIVE,
    	CS_MEM_EXCLUSIVE,
    	CS_MEM_HARDWALL,
    	CS_MEMORY_MIGRATE,
    	CS_SCHED_LOAD_BALANCE,
    	CS_SPREAD_PAGE,
    	CS_SPREAD_SLAB,
    } cpuset_flagbits_t;
    
    /* convenient tests for these bits */
    static inline bool is_cpuset_online(const struct cpuset *cs)
    {
    	return test_bit(CS_ONLINE, &cs->flags);
    }
    
    static inline int is_cpu_exclusive(const struct cpuset *cs)
    {
    	return test_bit(CS_CPU_EXCLUSIVE, &cs->flags);
    }
    
    static inline int is_mem_exclusive(const struct cpuset *cs)
    {
    	return test_bit(CS_MEM_EXCLUSIVE, &cs->flags);
    }
    
    static inline int is_mem_hardwall(const struct cpuset *cs)
    {
    	return test_bit(CS_MEM_HARDWALL, &cs->flags);
    }
    
    static inline int is_sched_load_balance(const struct cpuset *cs)
    {
    	return test_bit(CS_SCHED_LOAD_BALANCE, &cs->flags);
    }
    
    static inline int is_memory_migrate(const struct cpuset *cs)
    {
    	return test_bit(CS_MEMORY_MIGRATE, &cs->flags);
    }
    
    static inline int is_spread_page(const struct cpuset *cs)
    {
    	return test_bit(CS_SPREAD_PAGE, &cs->flags);
    }
    
    static inline int is_spread_slab(const struct cpuset *cs)
    {
    	return test_bit(CS_SPREAD_SLAB, &cs->flags);
    }
    
    static struct cpuset top_cpuset = {
    	.flags = ((1 << CS_ONLINE) | (1 << CS_CPU_EXCLUSIVE) |
    		  (1 << CS_MEM_EXCLUSIVE)),
    };
    
    /**
     * cpuset_for_each_child - traverse online children of a cpuset
     * @child_cs: loop cursor pointing to the current child
     * @pos_css: used for iteration
     * @parent_cs: target cpuset to walk children of
     *
     * Walk @child_cs through the online children of @parent_cs.  Must be used
     * with RCU read locked.
     */
    #define cpuset_for_each_child(child_cs, pos_css, parent_cs)		\
    	css_for_each_child((pos_css), &(parent_cs)->css)		\
    		if (is_cpuset_online(((child_cs) = css_cs((pos_css)))))
    
    /**
     * cpuset_for_each_descendant_pre - pre-order walk of a cpuset's descendants
     * @des_cs: loop cursor pointing to the current descendant
     * @pos_css: used for iteration
     * @root_cs: target cpuset to walk ancestor of
     *
     * Walk @des_cs through the online descendants of @root_cs.  Must be used
     * with RCU read locked.  The caller may modify @pos_css by calling
     * css_rightmost_descendant() to skip subtree.  @root_cs is included in the
     * iteration and the first node to be visited.
     */
    #define cpuset_for_each_descendant_pre(des_cs, pos_css, root_cs)	\
    	css_for_each_descendant_pre((pos_css), &(root_cs)->css)		\
    		if (is_cpuset_online(((des_cs) = css_cs((pos_css)))))
    
    /*
     * There are two global locks guarding cpuset structures - cpuset_mutex and
     * callback_lock. We also require taking task_lock() when dereferencing a
     * task's cpuset pointer. See "The task_lock() exception", at the end of this
     * comment.
     *
     * A task must hold both locks to modify cpusets.  If a task holds
     * cpuset_mutex, then it blocks others wanting that mutex, ensuring that it
     * is the only task able to also acquire callback_lock and be able to
     * modify cpusets.  It can perform various checks on the cpuset structure
     * first, knowing nothing will change.  It can also allocate memory while
     * just holding cpuset_mutex.  While it is performing these checks, various
     * callback routines can briefly acquire callback_lock to query cpusets.
     * Once it is ready to make the changes, it takes callback_lock, blocking
     * everyone else.
     *
     * Calls to the kernel memory allocator can not be made while holding
     * callback_lock, as that would risk double tripping on callback_lock
     * from one of the callbacks into the cpuset code from within
     * __alloc_pages().
     *
     * If a task is only holding callback_lock, then it has read-only
     * access to cpusets.
     *
     * Now, the task_struct fields mems_allowed and mempolicy may be changed
     * by other task, we use alloc_lock in the task_struct fields to protect
     * them.
     *
     * The cpuset_common_file_read() handlers only hold callback_lock across
     * small pieces of code, such as when reading out possibly multi-word
     * cpumasks and nodemasks.
     *
     * Accessing a task's cpuset should be done in accordance with the
     * guidelines for accessing subsystem state in kernel/cgroup.c
     */
    
    static DEFINE_MUTEX(cpuset_mutex);
    static DEFINE_SPINLOCK(callback_lock);
    
    static struct workqueue_struct *cpuset_migrate_mm_wq;
    
    /*
     * CPU / memory hotplug is handled asynchronously.
     */
    static void cpuset_hotplug_workfn(struct work_struct *work);
    static DECLARE_WORK(cpuset_hotplug_work, cpuset_hotplug_workfn);
    
    static DECLARE_WAIT_QUEUE_HEAD(cpuset_attach_wq);
    
    /*
     * This is ugly, but preserves the userspace API for existing cpuset
     * users. If someone tries to mount the "cpuset" filesystem, we
     * silently switch it to mount "cgroup" instead
     */
    static struct dentry *cpuset_mount(struct file_system_type *fs_type,
    			 int flags, const char *unused_dev_name, void *data)
    {
    	struct file_system_type *cgroup_fs = get_fs_type("cgroup");
    	struct dentry *ret = ERR_PTR(-ENODEV);
    	if (cgroup_fs) {
    		char mountopts[] =
    			"cpuset,noprefix,"
    			"release_agent=/sbin/cpuset_release_agent";
    		ret = cgroup_fs->mount(cgroup_fs, flags,
    					   unused_dev_name, mountopts);
    		put_filesystem(cgroup_fs);
    	}
    	return ret;
    }
    
    static struct file_system_type cpuset_fs_type = {
    	.name = "cpuset",
    	.mount = cpuset_mount,
    };
    
    /*
     * Return in pmask the portion of a cpusets's cpus_allowed that
     * are online.  If none are online, walk up the cpuset hierarchy
     * until we find one that does have some online cpus.  The top
     * cpuset always has some cpus online.
     *
     * One way or another, we guarantee to return some non-empty subset
     * of cpu_online_mask.
     *
     * Call with callback_lock or cpuset_mutex held.
     */
    static void guarantee_online_cpus(struct cpuset *cs, struct cpumask *pmask)
    {
    	while (!cpumask_intersects(cs->effective_cpus, cpu_online_mask))
    		cs = parent_cs(cs);
    	cpumask_and(pmask, cs->effective_cpus, cpu_online_mask);
    }
    
    /*
     * Return in *pmask the portion of a cpusets's mems_allowed that
     * are online, with memory.  If none are online with memory, walk
     * up the cpuset hierarchy until we find one that does have some
     * online mems.  The top cpuset always has some mems online.
     *
     * One way or another, we guarantee to return some non-empty subset
     * of node_states[N_MEMORY].
     *
     * Call with callback_lock or cpuset_mutex held.
     */
    static void guarantee_online_mems(struct cpuset *cs, nodemask_t *pmask)
    {
    	while (!nodes_intersects(cs->effective_mems, node_states[N_MEMORY]))
    		cs = parent_cs(cs);
    	nodes_and(*pmask, cs->effective_mems, node_states[N_MEMORY]);
    }
    
    /*
     * update task's spread flag if cpuset's page/slab spread flag is set
     *
     * Call with callback_lock or cpuset_mutex held.
     */
    static void cpuset_update_task_spread_flag(struct cpuset *cs,
    					struct task_struct *tsk)
    {
    	if (is_spread_page(cs))
    		task_set_spread_page(tsk);
    	else
    		task_clear_spread_page(tsk);
    
    	if (is_spread_slab(cs))
    		task_set_spread_slab(tsk);
    	else
    		task_clear_spread_slab(tsk);
    }
    
    /*
     * is_cpuset_subset(p, q) - Is cpuset p a subset of cpuset q?
     *
     * One cpuset is a subset of another if all its allowed CPUs and
     * Memory Nodes are a subset of the other, and its exclusive flags
     * are only set if the other's are set.  Call holding cpuset_mutex.
     */
    
    static int is_cpuset_subset(const struct cpuset *p, const struct cpuset *q)
    {
    	return	cpumask_subset(p->cpus_allowed, q->cpus_allowed) &&
    		nodes_subset(p->mems_allowed, q->mems_allowed) &&
    		is_cpu_exclusive(p) <= is_cpu_exclusive(q) &&
    		is_mem_exclusive(p) <= is_mem_exclusive(q);
    }
    
    /**
     * alloc_trial_cpuset - allocate a trial cpuset
     * @cs: the cpuset that the trial cpuset duplicates
     */
    static struct cpuset *alloc_trial_cpuset(struct cpuset *cs)
    {
    	struct cpuset *trial;
    
    	trial = kmemdup(cs, sizeof(*cs), GFP_KERNEL);
    	if (!trial)
    		return NULL;
    
    	if (!alloc_cpumask_var(&trial->cpus_allowed, GFP_KERNEL))
    		goto free_cs;
    	if (!alloc_cpumask_var(&trial->effective_cpus, GFP_KERNEL))
    		goto free_cpus;
    
    	cpumask_copy(trial->cpus_allowed, cs->cpus_allowed);
    	cpumask_copy(trial->effective_cpus, cs->effective_cpus);
    	return trial;
    
    free_cpus:
    	free_cpumask_var(trial->cpus_allowed);
    free_cs:
    	kfree(trial);
    	return NULL;
    }
    
    /**
     * free_trial_cpuset - free the trial cpuset
     * @trial: the trial cpuset to be freed
     */
    static void free_trial_cpuset(struct cpuset *trial)
    {
    	free_cpumask_var(trial->effective_cpus);
    	free_cpumask_var(trial->cpus_allowed);
    	kfree(trial);
    }
    
    /*
     * validate_change() - Used to validate that any proposed cpuset change
     *		       follows the structural rules for cpusets.
     *
     * If we replaced the flag and mask values of the current cpuset
     * (cur) with those values in the trial cpuset (trial), would
     * our various subset and exclusive rules still be valid?  Presumes
     * cpuset_mutex held.
     *
     * 'cur' is the address of an actual, in-use cpuset.  Operations
     * such as list traversal that depend on the actual address of the
     * cpuset in the list must use cur below, not trial.
     *
     * 'trial' is the address of bulk structure copy of cur, with
     * perhaps one or more of the fields cpus_allowed, mems_allowed,
     * or flags changed to new, trial values.
     *
     * Return 0 if valid, -errno if not.
     */
    
    static int validate_change(struct cpuset *cur, struct cpuset *trial)
    {
    	struct cgroup_subsys_state *css;
    	struct cpuset *c, *par;
    	int ret;
    
    	rcu_read_lock();
    
    	/* Each of our child cpusets must be a subset of us */
    	ret = -EBUSY;
    	cpuset_for_each_child(c, css, cur)
    		if (!is_cpuset_subset(c, trial))
    			goto out;
    
    	/* Remaining checks don't apply to root cpuset */
    	ret = 0;
    	if (cur == &top_cpuset)
    		goto out;
    
    	par = parent_cs(cur);
    
    	/* On legacy hiearchy, we must be a subset of our parent cpuset. */
    	ret = -EACCES;
    	if (!cgroup_subsys_on_dfl(cpuset_cgrp_subsys) &&
    	    !is_cpuset_subset(trial, par))
    		goto out;
    
    	/*
    	 * If either I or some sibling (!= me) is exclusive, we can't
    	 * overlap
    	 */
    	ret = -EINVAL;
    	cpuset_for_each_child(c, css, par) {
    		if ((is_cpu_exclusive(trial) || is_cpu_exclusive(c)) &&
    		    c != cur &&
    		    cpumask_intersects(trial->cpus_allowed, c->cpus_allowed))
    			goto out;
    		if ((is_mem_exclusive(trial) || is_mem_exclusive(c)) &&
    		    c != cur &&
    		    nodes_intersects(trial->mems_allowed, c->mems_allowed))
    			goto out;
    	}
    
    	/*
    	 * Cpusets with tasks - existing or newly being attached - can't
    	 * be changed to have empty cpus_allowed or mems_allowed.
    	 */
    	ret = -ENOSPC;
    	if ((cgroup_is_populated(cur->css.cgroup) || cur->attach_in_progress)) {
    		if (!cpumask_empty(cur->cpus_allowed) &&
    		    cpumask_empty(trial->cpus_allowed))
    			goto out;
    		if (!nodes_empty(cur->mems_allowed) &&
    		    nodes_empty(trial->mems_allowed))
    			goto out;
    	}
    
    	/*
    	 * We can't shrink if we won't have enough room for SCHED_DEADLINE
    	 * tasks.
    	 */
    	ret = -EBUSY;
    	if (is_cpu_exclusive(cur) &&
    	    !cpuset_cpumask_can_shrink(cur->cpus_allowed,
    				       trial->cpus_allowed))
    		goto out;
    
    	ret = 0;
    out:
    	rcu_read_unlock();
    	return ret;
    }
    
    #ifdef CONFIG_SMP
    /*
     * Helper routine for generate_sched_domains().
     * Do cpusets a, b have overlapping effective cpus_allowed masks?
     */
    static int cpusets_overlap(struct cpuset *a, struct cpuset *b)
    {
    	return cpumask_intersects(a->effective_cpus, b->effective_cpus);
    }
    
    static void
    update_domain_attr(struct sched_domain_attr *dattr, struct cpuset *c)
    {
    	if (dattr->relax_domain_level < c->relax_domain_level)
    		dattr->relax_domain_level = c->relax_domain_level;
    	return;
    }
    
    static void update_domain_attr_tree(struct sched_domain_attr *dattr,
    				    struct cpuset *root_cs)
    {
    	struct cpuset *cp;
    	struct cgroup_subsys_state *pos_css;
    
    	rcu_read_lock();
    	cpuset_for_each_descendant_pre(cp, pos_css, root_cs) {
    		/* skip the whole subtree if @cp doesn't have any CPU */
    		if (cpumask_empty(cp->cpus_allowed)) {
    			pos_css = css_rightmost_descendant(pos_css);
    			continue;
    		}
    
    		if (is_sched_load_balance(cp))
    			update_domain_attr(dattr, cp);
    	}
    	rcu_read_unlock();
    }
    
    /*
     * generate_sched_domains()
     *
     * This function builds a partial partition of the systems CPUs
     * A 'partial partition' is a set of non-overlapping subsets whose
     * union is a subset of that set.
     * The output of this function needs to be passed to kernel/sched/core.c
     * partition_sched_domains() routine, which will rebuild the scheduler's
     * load balancing domains (sched domains) as specified by that partial
     * partition.
     *
     * See "What is sched_load_balance" in Documentation/cgroups/cpusets.txt
     * for a background explanation of this.
     *
     * Does not return errors, on the theory that the callers of this
     * routine would rather not worry about failures to rebuild sched
     * domains when operating in the severe memory shortage situations
     * that could cause allocation failures below.
     *
     * Must be called with cpuset_mutex held.
     *
     * The three key local variables below are:
     *    q  - a linked-list queue of cpuset pointers, used to implement a
     *	   top-down scan of all cpusets.  This scan loads a pointer
     *	   to each cpuset marked is_sched_load_balance into the
     *	   array 'csa'.  For our purposes, rebuilding the schedulers
     *	   sched domains, we can ignore !is_sched_load_balance cpusets.
     *  csa  - (for CpuSet Array) Array of pointers to all the cpusets
     *	   that need to be load balanced, for convenient iterative
     *	   access by the subsequent code that finds the best partition,
     *	   i.e the set of domains (subsets) of CPUs such that the
     *	   cpus_allowed of every cpuset marked is_sched_load_balance
     *	   is a subset of one of these domains, while there are as
     *	   many such domains as possible, each as small as possible.
     * doms  - Conversion of 'csa' to an array of cpumasks, for passing to
     *	   the kernel/sched/core.c routine partition_sched_domains() in a
     *	   convenient format, that can be easily compared to the prior
     *	   value to determine what partition elements (sched domains)
     *	   were changed (added or removed.)
     *
     * Finding the best partition (set of domains):
     *	The triple nested loops below over i, j, k scan over the
     *	load balanced cpusets (using the array of cpuset pointers in
     *	csa[]) looking for pairs of cpusets that have overlapping
     *	cpus_allowed, but which don't have the same 'pn' partition
     *	number and gives them in the same partition number.  It keeps
     *	looping on the 'restart' label until it can no longer find
     *	any such pairs.
     *
     *	The union of the cpus_allowed masks from the set of
     *	all cpusets having the same 'pn' value then form the one
     *	element of the partition (one sched domain) to be passed to
     *	partition_sched_domains().
     */
    static int generate_sched_domains(cpumask_var_t **domains,
    			struct sched_domain_attr **attributes)
    {
    	struct cpuset *cp;	/* scans q */
    	struct cpuset **csa;	/* array of all cpuset ptrs */
    	int csn;		/* how many cpuset ptrs in csa so far */
    	int i, j, k;		/* indices for partition finding loops */
    	cpumask_var_t *doms;	/* resulting partition; i.e. sched domains */
    	cpumask_var_t non_isolated_cpus;  /* load balanced CPUs */
    	struct sched_domain_attr *dattr;  /* attributes for custom domains */
    	int ndoms = 0;		/* number of sched domains in result */
    	int nslot;		/* next empty doms[] struct cpumask slot */
    	struct cgroup_subsys_state *pos_css;
    
    	doms = NULL;
    	dattr = NULL;
    	csa = NULL;
    
    	if (!alloc_cpumask_var(&non_isolated_cpus, GFP_KERNEL))
    		goto done;
    	cpumask_andnot(non_isolated_cpus, cpu_possible_mask, cpu_isolated_map);
    
    	/* Special case for the 99% of systems with one, full, sched domain */
    	if (is_sched_load_balance(&top_cpuset)) {
    		ndoms = 1;
    		doms = alloc_sched_domains(ndoms);
    		if (!doms)
    			goto done;
    
    		dattr = kmalloc(sizeof(struct sched_domain_attr), GFP_KERNEL);
    		if (dattr) {
    			*dattr = SD_ATTR_INIT;
    			update_domain_attr_tree(dattr, &top_cpuset);
    		}
    		cpumask_and(doms[0], top_cpuset.effective_cpus,
    				     non_isolated_cpus);
    
    		goto done;
    	}
    
    	csa = kmalloc(nr_cpusets() * sizeof(cp), GFP_KERNEL);
    	if (!csa)
    		goto done;
    	csn = 0;
    
    	rcu_read_lock();
    	cpuset_for_each_descendant_pre(cp, pos_css, &top_cpuset) {
    		if (cp == &top_cpuset)
    			continue;
    		/*
    		 * Continue traversing beyond @cp iff @cp has some CPUs and
    		 * isn't load balancing.  The former is obvious.  The
    		 * latter: All child cpusets contain a subset of the
    		 * parent's cpus, so just skip them, and then we call
    		 * update_domain_attr_tree() to calc relax_domain_level of
    		 * the corresponding sched domain.
    		 */
    		if (!cpumask_empty(cp->cpus_allowed) &&
    		    !(is_sched_load_balance(cp) &&
    		      cpumask_intersects(cp->cpus_allowed, non_isolated_cpus)))
    			continue;
    
    		if (is_sched_load_balance(cp))
    			csa[csn++] = cp;
    
    		/* skip @cp's subtree */
    		pos_css = css_rightmost_descendant(pos_css);
    	}
    	rcu_read_unlock();
    
    	for (i = 0; i < csn; i++)
    		csa[i]->pn = i;
    	ndoms = csn;
    
    restart:
    	/* Find the best partition (set of sched domains) */
    	for (i = 0; i < csn; i++) {
    		struct cpuset *a = csa[i];
    		int apn = a->pn;
    
    		for (j = 0; j < csn; j++) {
    			struct cpuset *b = csa[j];
    			int bpn = b->pn;
    
    			if (apn != bpn && cpusets_overlap(a, b)) {
    				for (k = 0; k < csn; k++) {
    					struct cpuset *c = csa[k];
    
    					if (c->pn == bpn)
    						c->pn = apn;
    				}
    				ndoms--;	/* one less element */
    				goto restart;
    			}
    		}
    	}
    
    	/*
    	 * Now we know how many domains to create.
    	 * Convert <csn, csa> to <ndoms, doms> and populate cpu masks.
    	 */
    	doms = alloc_sched_domains(ndoms);
    	if (!doms)
    		goto done;
    
    	/*
    	 * The rest of the code, including the scheduler, can deal with
    	 * dattr==NULL case. No need to abort if alloc fails.
    	 */
    	dattr = kmalloc(ndoms * sizeof(struct sched_domain_attr), GFP_KERNEL);
    
    	for (nslot = 0, i = 0; i < csn; i++) {
    		struct cpuset *a = csa[i];
    		struct cpumask *dp;
    		int apn = a->pn;
    
    		if (apn < 0) {
    			/* Skip completed partitions */
    			continue;
    		}
    
    		dp = doms[nslot];
    
    		if (nslot == ndoms) {
    			static int warnings = 10;
    			if (warnings) {
    				pr_warn("rebuild_sched_domains confused: nslot %d, ndoms %d, csn %d, i %d, apn %d\n",
    					nslot, ndoms, csn, i, apn);
    				warnings--;
    			}
    			continue;
    		}
    
    		cpumask_clear(dp);
    		if (dattr)
    			*(dattr + nslot) = SD_ATTR_INIT;
    		for (j = i; j < csn; j++) {
    			struct cpuset *b = csa[j];
    
    			if (apn == b->pn) {
    				cpumask_or(dp, dp, b->effective_cpus);
    				cpumask_and(dp, dp, non_isolated_cpus);
    				if (dattr)
    					update_domain_attr_tree(dattr + nslot, b);
    
    				/* Done with this partition */
    				b->pn = -1;
    			}
    		}
    		nslot++;
    	}
    	BUG_ON(nslot != ndoms);
    
    done:
    	free_cpumask_var(non_isolated_cpus);
    	kfree(csa);
    
    	/*
    	 * Fallback to the default domain if kmalloc() failed.
    	 * See comments in partition_sched_domains().
    	 */
    	if (doms == NULL)
    		ndoms = 1;
    
    	*domains    = doms;
    	*attributes = dattr;
    	return ndoms;
    }
    
    /*
     * Rebuild scheduler domains.
     *
     * If the flag 'sched_load_balance' of any cpuset with non-empty
     * 'cpus' changes, or if the 'cpus' allowed changes in any cpuset
     * which has that flag enabled, or if any cpuset with a non-empty
     * 'cpus' is removed, then call this routine to rebuild the
     * scheduler's dynamic sched domains.
     *
     * Call with cpuset_mutex held.  Takes get_online_cpus().
     */
    static void rebuild_sched_domains_locked(void)
    {
    	struct sched_domain_attr *attr;
    	cpumask_var_t *doms;
    	int ndoms;
    
    	lockdep_assert_held(&cpuset_mutex);
    	get_online_cpus();
    
    	/*
    	 * We have raced with CPU hotplug. Don't do anything to avoid
    	 * passing doms with offlined cpu to partition_sched_domains().
    	 * Anyways, hotplug work item will rebuild sched domains.
    	 */
    	if (!cpumask_equal(top_cpuset.effective_cpus, cpu_active_mask))
    		goto out;
    
    	/* Generate domain masks and attrs */
    	ndoms = generate_sched_domains(&doms, &attr);
    
    	/* Have scheduler rebuild the domains */
    	partition_sched_domains(ndoms, doms, attr);
    out:
    	put_online_cpus();
    }
    #else /* !CONFIG_SMP */
    static void rebuild_sched_domains_locked(void)
    {
    }
    #endif /* CONFIG_SMP */
    
    void rebuild_sched_domains(void)
    {
    	mutex_lock(&cpuset_mutex);
    	rebuild_sched_domains_locked();
    	mutex_unlock(&cpuset_mutex);
    }
    
    /**
     * update_tasks_cpumask - Update the cpumasks of tasks in the cpuset.
     * @cs: the cpuset in which each task's cpus_allowed mask needs to be changed
     *
     * Iterate through each task of @cs updating its cpus_allowed to the
     * effective cpuset's.  As this function is called with cpuset_mutex held,
     * cpuset membership stays stable.
     */
    static void update_tasks_cpumask(struct cpuset *cs)
    {
    	struct css_task_iter it;
    	struct task_struct *task;
    
    	css_task_iter_start(&cs->css, &it);
    	while ((task = css_task_iter_next(&it)))
    		set_cpus_allowed_ptr(task, cs->effective_cpus);
    	css_task_iter_end(&it);
    }
    
    /*
     * update_cpumasks_hier - Update effective cpumasks and tasks in the subtree
     * @cs: the cpuset to consider
     * @new_cpus: temp variable for calculating new effective_cpus
     *
     * When congifured cpumask is changed, the effective cpumasks of this cpuset
     * and all its descendants need to be updated.
     *
     * On legacy hierachy, effective_cpus will be the same with cpu_allowed.
     *
     * Called with cpuset_mutex held
     */
    static void update_cpumasks_hier(struct cpuset *cs, struct cpumask *new_cpus)
    {
    	struct cpuset *cp;
    	struct cgroup_subsys_state *pos_css;
    	bool need_rebuild_sched_domains = false;
    
    	rcu_read_lock();
    	cpuset_for_each_descendant_pre(cp, pos_css, cs) {
    		struct cpuset *parent = parent_cs(cp);
    
    		cpumask_and(new_cpus, cp->cpus_allowed, parent->effective_cpus);
    
    		/*
    		 * If it becomes empty, inherit the effective mask of the
    		 * parent, which is guaranteed to have some CPUs.
    		 */
    		if (cgroup_subsys_on_dfl(cpuset_cgrp_subsys) &&
    		    cpumask_empty(new_cpus))
    			cpumask_copy(new_cpus, parent->effective_cpus);
    
    		/* Skip the whole subtree if the cpumask remains the same. */
    		if (cpumask_equal(new_cpus, cp->effective_cpus)) {
    			pos_css = css_rightmost_descendant(pos_css);
    			continue;
    		}
    
    		if (!css_tryget_online(&cp->css))
    			continue;
    		rcu_read_unlock();
    
    		spin_lock_irq(&callback_lock);
    		cpumask_copy(cp->effective_cpus, new_cpus);
    		spin_unlock_irq(&callback_lock);
    
    		WARN_ON(!cgroup_subsys_on_dfl(cpuset_cgrp_subsys) &&
    			!cpumask_equal(cp->cpus_allowed, cp->effective_cpus));
    
    		update_tasks_cpumask(cp);
    
    		/*
    		 * If the effective cpumask of any non-empty cpuset is changed,
    		 * we need to rebuild sched domains.
    		 */
    		if (!cpumask_empty(cp->cpus_allowed) &&
    		    is_sched_load_balance(cp))
    			need_rebuild_sched_domains = true;
    
    		rcu_read_lock();
    		css_put(&cp->css);
    	}
    	rcu_read_unlock();
    
    	if (need_rebuild_sched_domains)
    		rebuild_sched_domains_locked();
    }
    
    /**
     * update_cpumask - update the cpus_allowed mask of a cpuset and all tasks in it
     * @cs: the cpuset to consider
     * @trialcs: trial cpuset
     * @buf: buffer of cpu numbers written to this cpuset
     */
    static int update_cpumask(struct cpuset *cs, struct cpuset *trialcs,
    			  const char *buf)
    {
    	int retval;
    
    	/* top_cpuset.cpus_allowed tracks cpu_online_mask; it's read-only */
    	if (cs == &top_cpuset)
    		return -EACCES;
    
    	/*
    	 * An empty cpus_allowed is ok only if the cpuset has no tasks.
    	 * Since cpulist_parse() fails on an empty mask, we special case
    	 * that parsing.  The validate_change() call ensures that cpusets
    	 * with tasks have cpus.
    	 */
    	if (!*buf) {
    		cpumask_clear(trialcs->cpus_allowed);
    	} else {
    		retval = cpulist_parse(buf, trialcs->cpus_allowed);
    		if (retval < 0)
    			return retval;
    
    		if (!cpumask_subset(trialcs->cpus_allowed,
    				    top_cpuset.cpus_allowed))
    			return -EINVAL;
    	}
    
    	/* Nothing to do if the cpus didn't change */
    	if (cpumask_equal(cs->cpus_allowed, trialcs->cpus_allowed))
    		return 0;
    
    	retval = validate_change(cs, trialcs);
    	if (retval < 0)
    		return retval;
    
    	spin_lock_irq(&callback_lock);
    	cpumask_copy(cs->cpus_allowed, trialcs->cpus_allowed);
    	spin_unlock_irq(&callback_lock);
    
    	/* use trialcs->cpus_allowed as a temp variable */
    	update_cpumasks_hier(cs, trialcs->cpus_allowed);
    	return 0;
    }
    
    /*
     * Migrate memory region from one set of nodes to another.  This is
     * performed asynchronously as it can be called from process migration path
     * holding locks involved in process management.  All mm migrations are
     * performed in the queued order and can be waited for by flushing
     * cpuset_migrate_mm_wq.
     */
    
    struct cpuset_migrate_mm_work {
    	struct work_struct	work;
    	struct mm_struct	*mm;
    	nodemask_t		from;
    	nodemask_t		to;
    };
    
    static void cpuset_migrate_mm_workfn(struct work_struct *work)
    {
    	struct cpuset_migrate_mm_work *mwork =
    		container_of(work, struct cpuset_migrate_mm_work, work);
    
    	/* on a wq worker, no need to worry about %current's mems_allowed */
    	do_migrate_pages(mwork->mm, &mwork->from, &mwork->to, MPOL_MF_MOVE_ALL);
    	mmput(mwork->mm);
    	kfree(mwork);
    }
    
    static void cpuset_migrate_mm(struct mm_struct *mm, const nodemask_t *from,
    							const nodemask_t *to)
    {
    	struct cpuset_migrate_mm_work *mwork;
    
    	mwork = kzalloc(sizeof(*mwork), GFP_KERNEL);
    	if (mwork) {
    		mwork->mm = mm;
    		mwork->from = *from;
    		mwork->to = *to;
    		INIT_WORK(&mwork->work, cpuset_migrate_mm_workfn);
    		queue_work(cpuset_migrate_mm_wq, &mwork->work);
    	} else {
    		mmput(mm);
    	}
    }
    
    static void cpuset_post_attach(void)
    {
    	flush_workqueue(cpuset_migrate_mm_wq);
    }
    
    /*
     * cpuset_change_task_nodemask - change task's mems_allowed and mempolicy
     * @tsk: the task to change
     * @newmems: new nodes that the task will be set
     *
     * In order to avoid seeing no nodes if the old and new nodes are disjoint,
     * we structure updates as setting all new allowed nodes, then clearing newly
     * disallowed ones.
     */
    static void cpuset_change_task_nodemask(struct task_struct *tsk,
    					nodemask_t *newmems)
    {
    	bool need_loop;
    
    	task_lock(tsk);
    	/*
    	 * Determine if a loop is necessary if another thread is doing
    	 * read_mems_allowed_begin().  If at least one node remains unchanged and
    	 * tsk does not have a mempolicy, then an empty nodemask will not be
    	 * possible when mems_allowed is larger than a word.
    	 */
    	need_loop = task_has_mempolicy(tsk) ||
    			!nodes_intersects(*newmems, tsk->mems_allowed);
    
    	if (need_loop) {
    		local_irq_disable();
    		write_seqcount_begin(&tsk->mems_allowed_seq);
    	}
    
    	nodes_or(tsk->mems_allowed, tsk->mems_allowed, *newmems);
    	mpol_rebind_task(tsk, newmems, MPOL_REBIND_STEP1);
    
    	mpol_rebind_task(tsk, newmems, MPOL_REBIND_STEP2);
    	tsk->mems_allowed = *newmems;
    
    	if (need_loop) {
    		write_seqcount_end(&tsk->mems_allowed_seq);
    		local_irq_enable();
    	}
    
    	task_unlock(tsk);
    }
    
    static void *cpuset_being_rebound;
    
    /**
     * update_tasks_nodemask - Update the nodemasks of tasks in the cpuset.
     * @cs: the cpuset in which each task's mems_allowed mask needs to be changed
     *
     * Iterate through each task of @cs updating its mems_allowed to the
     * effective cpuset's.  As this function is called with cpuset_mutex held,
     * cpuset membership stays stable.
     */
    static void update_tasks_nodemask(struct cpuset *cs)
    {
    	static nodemask_t newmems;	/* protected by cpuset_mutex */
    	struct css_task_iter it;
    	struct task_struct *task;
    
    	cpuset_being_rebound = cs;		/* causes mpol_dup() rebind */
    
    	guarantee_online_mems(cs, &newmems);
    
    	/*
    	 * The mpol_rebind_mm() call takes mmap_sem, which we couldn't
    	 * take while holding tasklist_lock.  Forks can happen - the
    	 * mpol_dup() cpuset_being_rebound check will catch such forks,
    	 * and rebind their vma mempolicies too.  Because we still hold
    	 * the global cpuset_mutex, we know that no other rebind effort
    	 * will be contending for the global variable cpuset_being_rebound.
    	 * It's ok if we rebind the same mm twice; mpol_rebind_mm()
    	 * is idempotent.  Also migrate pages in each mm to new nodes.
    	 */
    	css_task_iter_start(&cs->css, &it);
    	while ((task = css_task_iter_next(&it))) {
    		struct mm_struct *mm;
    		bool migrate;
    
    		cpuset_change_task_nodemask(task, &newmems);
    
    		mm = get_task_mm(task);
    		if (!mm)
    			continue;
    
    		migrate = is_memory_migrate(cs);
    
    		mpol_rebind_mm(mm, &cs->mems_allowed);
    		if (migrate)
    			cpuset_migrate_mm(mm, &cs->old_mems_allowed, &newmems);
    		else
    			mmput(mm);
    	}
    	css_task_iter_end(&it);
    
    	/*
    	 * All the tasks' nodemasks have been updated, update
    	 * cs->old_mems_allowed.
    	 */
    	cs->old_mems_allowed = newmems;
    
    	/* We're done rebinding vmas to this cpuset's new mems_allowed. */
    	cpuset_being_rebound = NULL;
    }
    
    /*
     * update_nodemasks_hier - Update effective nodemasks and tasks in the subtree
     * @cs: the cpuset to consider
     * @new_mems: a temp variable for calculating new effective_mems
     *
     * When configured nodemask is changed, the effective nodemasks of this cpuset
     * and all its descendants need to be updated.
     *
     * On legacy hiearchy, effective_mems will be the same with mems_allowed.
     *
     * Called with cpuset_mutex held
     */
    static void update_nodemasks_hier(struct cpuset *cs, nodemask_t *new_mems)
    {
    	struct cpuset *cp;
    	struct cgroup_subsys_state *pos_css;
    
    	rcu_read_lock();
    	cpuset_for_each_descendant_pre(cp, pos_css, cs) {
    		struct cpuset *parent = parent_cs(cp);
    
    		nodes_and(*new_mems, cp->mems_allowed, parent->effective_mems);
    
    		/*
    		 * If it becomes empty, inherit the effective mask of the
    		 * parent, which is guaranteed to have some MEMs.
    		 */
    		if (cgroup_subsys_on_dfl(cpuset_cgrp_subsys) &&
    		    nodes_empty(*new_mems))
    			*new_mems = parent->effective_mems;
    
    		/* Skip the whole subtree if the nodemask remains the same. */
    		if (nodes_equal(*new_mems, cp->effective_mems)) {
    			pos_css = css_rightmost_descendant(pos_css);
    			continue;
    		}
    
    		if (!css_tryget_online(&cp->css))
    			continue;
    		rcu_read_unlock();
    
    		spin_lock_irq(&callback_lock);
    		cp->effective_mems = *new_mems;
    		spin_unlock_irq(&callback_lock);
    
    		WARN_ON(!cgroup_subsys_on_dfl(cpuset_cgrp_subsys) &&
    			!nodes_equal(cp->mems_allowed, cp->effective_mems));
    
    		update_tasks_nodemask(cp);
    
    		rcu_read_lock();
    		css_put(&cp->css);
    	}
    	rcu_read_unlock();
    }
    
    /*
     * Handle user request to change the 'mems' memory placement
     * of a cpuset.  Needs to validate the request, update the
     * cpusets mems_allowed, and for each task in the cpuset,
     * update mems_allowed and rebind task's mempolicy and any vma
     * mempolicies and if the cpuset is marked 'memory_migrate',
     * migrate the tasks pages to the new memory.
     *
     * Call with cpuset_mutex held. May take callback_lock during call.
     * Will take tasklist_lock, scan tasklist for tasks in cpuset cs,
     * lock each such tasks mm->mmap_sem, scan its vma's and rebind
     * their mempolicies to the cpusets new mems_allowed.
     */
    static int update_nodemask(struct cpuset *cs, struct cpuset *trialcs,
    			   const char *buf)
    {
    	int retval;
    
    	/*
    	 * top_cpuset.mems_allowed tracks node_stats[N_MEMORY];
    	 * it's read-only
    	 */
    	if (cs == &top_cpuset) {
    		retval = -EACCES;
    		goto done;
    	}
    
    	/*
    	 * An empty mems_allowed is ok iff there are no tasks in the cpuset.
    	 * Since nodelist_parse() fails on an empty mask, we special case
    	 * that parsing.  The validate_change() call ensures that cpusets
    	 * with tasks have memory.
    	 */
    	if (!*buf) {
    		nodes_clear(trialcs->mems_allowed);
    	} else {
    		retval = nodelist_parse(buf, trialcs->mems_allowed);
    		if (retval < 0)
    			goto done;
    
    		if (!nodes_subset(trialcs->mems_allowed,
    				  top_cpuset.mems_allowed)) {
    			retval = -EINVAL;
    			goto done;
    		}
    	}
    
    	if (nodes_equal(cs->mems_allowed, trialcs->mems_allowed)) {
    		retval = 0;		/* Too easy - nothing to do */
    		goto done;
    	}
    	retval = validate_change(cs, trialcs);
    	if (retval < 0)
    		goto done;
    
    	spin_lock_irq(&callback_lock);
    	cs->mems_allowed = trialcs->mems_allowed;
    	spin_unlock_irq(&callback_lock);
    
    	/* use trialcs->mems_allowed as a temp variable */
    	update_nodemasks_hier(cs, &trialcs->mems_allowed);
    done:
    	return retval;
    }
    
    int current_cpuset_is_being_rebound(void)
    {
    	int ret;
    
    	rcu_read_lock();
    	ret = task_cs(current) == cpuset_being_rebound;
    	rcu_read_unlock();
    
    	return ret;
    }
    
    static int update_relax_domain_level(struct cpuset *cs, s64 val)
    {
    #ifdef CONFIG_SMP
    	if (val < -1 || val >= sched_domain_level_max)
    		return -EINVAL;
    #endif
    
    	if (val != cs->relax_domain_level) {
    		cs->relax_domain_level = val;
    		if (!cpumask_empty(cs->cpus_allowed) &&
    		    is_sched_load_balance(cs))
    			rebuild_sched_domains_locked();
    	}
    
    	return 0;
    }
    
    /**
     * update_tasks_flags - update the spread flags of tasks in the cpuset.
     * @cs: the cpuset in which each task's spread flags needs to be changed
     *
     * Iterate through each task of @cs updating its spread flags.  As this
     * function is called with cpuset_mutex held, cpuset membership stays
     * stable.
     */
    static void update_tasks_flags(struct cpuset *cs)
    {
    	struct css_task_iter it;
    	struct task_struct *task;
    
    	css_task_iter_start(&cs->css, &it);
    	while ((task = css_task_iter_next(&it)))
    		cpuset_update_task_spread_flag(cs, task);
    	css_task_iter_end(&it);
    }
    
    /*
     * update_flag - read a 0 or a 1 in a file and update associated flag
     * bit:		the bit to update (see cpuset_flagbits_t)
     * cs:		the cpuset to update
     * turning_on: 	whether the flag is being set or cleared
     *
     * Call with cpuset_mutex held.
     */
    
    static int update_flag(cpuset_flagbits_t bit, struct cpuset *cs,
    		       int turning_on)
    {
    	struct cpuset *trialcs;
    	int balance_flag_changed;
    	int spread_flag_changed;
    	int err;
    
    	trialcs = alloc_trial_cpuset(cs);
    	if (!trialcs)
    		return -ENOMEM;
    
    	if (turning_on)
    		set_bit(bit, &trialcs->flags);
    	else
    		clear_bit(bit, &trialcs->flags);
    
    	err = validate_change(cs, trialcs);
    	if (err < 0)
    		goto out;
    
    	balance_flag_changed = (is_sched_load_balance(cs) !=
    				is_sched_load_balance(trialcs));
    
    	spread_flag_changed = ((is_spread_slab(cs) != is_spread_slab(trialcs))
    			|| (is_spread_page(cs) != is_spread_page(trialcs)));
    
    	spin_lock_irq(&callback_lock);
    	cs->flags = trialcs->flags;
    	spin_unlock_irq(&callback_lock);
    
    	if (!cpumask_empty(trialcs->cpus_allowed) && balance_flag_changed)
    		rebuild_sched_domains_locked();
    
    	if (spread_flag_changed)
    		update_tasks_flags(cs);
    out:
    	free_trial_cpuset(trialcs);
    	return err;
    }
    
    /*
     * Frequency meter - How fast is some event occurring?
     *
     * These routines manage a digitally filtered, constant time based,
     * event frequency meter.  There are four routines:
     *   fmeter_init() - initialize a frequency meter.
     *   fmeter_markevent() - called each time the event happens.
     *   fmeter_getrate() - returns the recent rate of such events.
     *   fmeter_update() - internal routine used to update fmeter.
     *
     * A common data structure is passed to each of these routines,
     * which is used to keep track of the state required to manage the
     * frequency meter and its digital filter.
     *
     * The filter works on the number of events marked per unit time.
     * The filter is single-pole low-pass recursive (IIR).  The time unit
     * is 1 second.  Arithmetic is done using 32-bit integers scaled to
     * simulate 3 decimal digits of precision (multiplied by 1000).
     *
     * With an FM_COEF of 933, and a time base of 1 second, the filter
     * has a half-life of 10 seconds, meaning that if the events quit
     * happening, then the rate returned from the fmeter_getrate()
     * will be cut in half each 10 seconds, until it converges to zero.
     *
     * It is not worth doing a real infinitely recursive filter.  If more
     * than FM_MAXTICKS ticks have elapsed since the last filter event,
     * just compute FM_MAXTICKS ticks worth, by which point the level
     * will be stable.
     *
     * Limit the count of unprocessed events to FM_MAXCNT, so as to avoid
     * arithmetic overflow in the fmeter_update() routine.
     *
     * Given the simple 32 bit integer arithmetic used, this meter works
     * best for reporting rates between one per millisecond (msec) and
     * one per 32 (approx) seconds.  At constant rates faster than one
     * per msec it maxes out at values just under 1,000,000.  At constant
     * rates between one per msec, and one per second it will stabilize
     * to a value N*1000, where N is the rate of events per second.
     * At constant rates between one per second and one per 32 seconds,
     * it will be choppy, moving up on the seconds that have an event,
     * and then decaying until the next event.  At rates slower than
     * about one in 32 seconds, it decays all the way back to zero between
     * each event.
     */
    
    #define FM_COEF 933		/* coefficient for half-life of 10 secs */
    #define FM_MAXTICKS ((u32)99)   /* useless computing more ticks than this */
    #define FM_MAXCNT 1000000	/* limit cnt to avoid overflow */
    #define FM_SCALE 1000		/* faux fixed point scale */
    
    /* Initialize a frequency meter */
    static void fmeter_init(struct fmeter *fmp)
    {
    	fmp->cnt = 0;
    	fmp->val = 0;
    	fmp->time = 0;
    	spin_lock_init(&fmp->lock);
    }
    
    /* Internal meter update - process cnt events and update value */
    static void fmeter_update(struct fmeter *fmp)
    {
    	time64_t now;
    	u32 ticks;
    
    	now = ktime_get_seconds();
    	ticks = now - fmp->time;
    
    	if (ticks == 0)
    		return;
    
    	ticks = min(FM_MAXTICKS, ticks);
    	while (ticks-- > 0)
    		fmp->val = (FM_COEF * fmp->val) / FM_SCALE;
    	fmp->time = now;
    
    	fmp->val += ((FM_SCALE - FM_COEF) * fmp->cnt) / FM_SCALE;
    	fmp->cnt = 0;
    }
    
    /* Process any previous ticks, then bump cnt by one (times scale). */
    static void fmeter_markevent(struct fmeter *fmp)
    {
    	spin_lock(&fmp->lock);
    	fmeter_update(fmp);
    	fmp->cnt = min(FM_MAXCNT, fmp->cnt + FM_SCALE);
    	spin_unlock(&fmp->lock);
    }
    
    /* Process any previous ticks, then return current value. */
    static int fmeter_getrate(struct fmeter *fmp)
    {
    	int val;
    
    	spin_lock(&fmp->lock);
    	fmeter_update(fmp);
    	val = fmp->val;
    	spin_unlock(&fmp->lock);
    	return val;
    }
    
    static struct cpuset *cpuset_attach_old_cs;
    
    /* Called by cgroups to determine if a cpuset is usable; cpuset_mutex held */
    static int cpuset_can_attach(struct cgroup_taskset *tset)
    {
    	struct cgroup_subsys_state *css;
    	struct cpuset *cs;
    	struct task_struct *task;
    	int ret;
    
    	/* used later by cpuset_attach() */
    	cpuset_attach_old_cs = task_cs(cgroup_taskset_first(tset, &css));
    	cs = css_cs(css);
    
    	mutex_lock(&cpuset_mutex);
    
    	/* allow moving tasks into an empty cpuset if on default hierarchy */
    	ret = -ENOSPC;
    	if (!cgroup_subsys_on_dfl(cpuset_cgrp_subsys) &&
    	    (cpumask_empty(cs->cpus_allowed) || nodes_empty(cs->mems_allowed)))
    		goto out_unlock;
    
    	cgroup_taskset_for_each(task, css, tset) {
    		ret = task_can_attach(task, cs->cpus_allowed);
    		if (ret)
    			goto out_unlock;
    		ret = security_task_setscheduler(task);
    		if (ret)
    			goto out_unlock;
    	}
    
    	/*
    	 * Mark attach is in progress.  This makes validate_change() fail
    	 * changes which zero cpus/mems_allowed.
    	 */
    	cs->attach_in_progress++;
    	ret = 0;
    out_unlock:
    	mutex_unlock(&cpuset_mutex);
    	return ret;
    }
    
    static void cpuset_cancel_attach(struct cgroup_taskset *tset)
    {
    	struct cgroup_subsys_state *css;
    	struct cpuset *cs;
    
    	cgroup_taskset_first(tset, &css);
    	cs = css_cs(css);
    
    	mutex_lock(&cpuset_mutex);
    	css_cs(css)->attach_in_progress--;
    	mutex_unlock(&cpuset_mutex);
    }
    
    /*
     * Protected by cpuset_mutex.  cpus_attach is used only by cpuset_attach()
     * but we can't allocate it dynamically there.  Define it global and
     * allocate from cpuset_init().
     */
    static cpumask_var_t cpus_attach;
    
    static void cpuset_attach(struct cgroup_taskset *tset)
    {
    	/* static buf protected by cpuset_mutex */
    	static nodemask_t cpuset_attach_nodemask_to;
    	struct task_struct *task;
    	struct task_struct *leader;
    	struct cgroup_subsys_state *css;
    	struct cpuset *cs;
    	struct cpuset *oldcs = cpuset_attach_old_cs;
    
    	cgroup_taskset_first(tset, &css);
    	cs = css_cs(css);
    
    	mutex_lock(&cpuset_mutex);
    
    	/* prepare for attach */
    	if (cs == &top_cpuset)
    		cpumask_copy(cpus_attach, cpu_possible_mask);
    	else
    		guarantee_online_cpus(cs, cpus_attach);
    
    	guarantee_online_mems(cs, &cpuset_attach_nodemask_to);
    
    	cgroup_taskset_for_each(task, css, tset) {
    		/*
    		 * can_attach beforehand should guarantee that this doesn't
    		 * fail.  TODO: have a better way to handle failure here
    		 */
    		WARN_ON_ONCE(set_cpus_allowed_ptr(task, cpus_attach));
    
    		cpuset_change_task_nodemask(task, &cpuset_attach_nodemask_to);
    		cpuset_update_task_spread_flag(cs, task);
    	}
    
    	/*
    	 * Change mm for all threadgroup leaders. This is expensive and may
    	 * sleep and should be moved outside migration path proper.
    	 */
    	cpuset_attach_nodemask_to = cs->effective_mems;
    	cgroup_taskset_for_each_leader(leader, css, tset) {
    		struct mm_struct *mm = get_task_mm(leader);
    
    		if (mm) {
    			mpol_rebind_mm(mm, &cpuset_attach_nodemask_to);
    
    			/*
    			 * old_mems_allowed is the same with mems_allowed
    			 * here, except if this task is being moved
    			 * automatically due to hotplug.  In that case
    			 * @mems_allowed has been updated and is empty, so
    			 * @old_mems_allowed is the right nodesets that we
    			 * migrate mm from.
    			 */
    			if (is_memory_migrate(cs))
    				cpuset_migrate_mm(mm, &oldcs->old_mems_allowed,
    						  &cpuset_attach_nodemask_to);
    			else
    				mmput(mm);
    		}
    	}
    
    	cs->old_mems_allowed = cpuset_attach_nodemask_to;
    
    	cs->attach_in_progress--;
    	if (!cs->attach_in_progress)
    		wake_up(&cpuset_attach_wq);
    
    	mutex_unlock(&cpuset_mutex);
    }
    
    /* The various types of files and directories in a cpuset file system */
    
    typedef enum {
    	FILE_MEMORY_MIGRATE,
    	FILE_CPULIST,
    	FILE_MEMLIST,
    	FILE_EFFECTIVE_CPULIST,
    	FILE_EFFECTIVE_MEMLIST,
    	FILE_CPU_EXCLUSIVE,
    	FILE_MEM_EXCLUSIVE,
    	FILE_MEM_HARDWALL,
    	FILE_SCHED_LOAD_BALANCE,
    	FILE_SCHED_RELAX_DOMAIN_LEVEL,
    	FILE_MEMORY_PRESSURE_ENABLED,
    	FILE_MEMORY_PRESSURE,
    	FILE_SPREAD_PAGE,
    	FILE_SPREAD_SLAB,
    } cpuset_filetype_t;
    
    static int cpuset_write_u64(struct cgroup_subsys_state *css, struct cftype *cft,
    			    u64 val)
    {
    	struct cpuset *cs = css_cs(css);
    	cpuset_filetype_t type = cft->private;
    	int retval = 0;
    
    	mutex_lock(&cpuset_mutex);
    	if (!is_cpuset_online(cs)) {
    		retval = -ENODEV;
    		goto out_unlock;
    	}
    
    	switch (type) {
    	case FILE_CPU_EXCLUSIVE:
    		retval = update_flag(CS_CPU_EXCLUSIVE, cs, val);
    		break;
    	case FILE_MEM_EXCLUSIVE:
    		retval = update_flag(CS_MEM_EXCLUSIVE, cs, val);
    		break;
    	case FILE_MEM_HARDWALL:
    		retval = update_flag(CS_MEM_HARDWALL, cs, val);
    		break;
    	case FILE_SCHED_LOAD_BALANCE:
    		retval = update_flag(CS_SCHED_LOAD_BALANCE, cs, val);
    		break;
    	case FILE_MEMORY_MIGRATE:
    		retval = update_flag(CS_MEMORY_MIGRATE, cs, val);
    		break;
    	case FILE_MEMORY_PRESSURE_ENABLED:
    		cpuset_memory_pressure_enabled = !!val;
    		break;
    	case FILE_SPREAD_PAGE:
    		retval = update_flag(CS_SPREAD_PAGE, cs, val);
    		break;
    	case FILE_SPREAD_SLAB:
    		retval = update_flag(CS_SPREAD_SLAB, cs, val);
    		break;
    	default:
    		retval = -EINVAL;
    		break;
    	}
    out_unlock:
    	mutex_unlock(&cpuset_mutex);
    	return retval;
    }
    
    static int cpuset_write_s64(struct cgroup_subsys_state *css, struct cftype *cft,
    			    s64 val)
    {
    	struct cpuset *cs = css_cs(css);
    	cpuset_filetype_t type = cft->private;
    	int retval = -ENODEV;
    
    	mutex_lock(&cpuset_mutex);
    	if (!is_cpuset_online(cs))
    		goto out_unlock;
    
    	switch (type) {
    	case FILE_SCHED_RELAX_DOMAIN_LEVEL:
    		retval = update_relax_domain_level(cs, val);
    		break;
    	default:
    		retval = -EINVAL;
    		break;
    	}
    out_unlock:
    	mutex_unlock(&cpuset_mutex);
    	return retval;
    }
    
    /*
     * Common handling for a write to a "cpus" or "mems" file.
     */
    static ssize_t cpuset_write_resmask(struct kernfs_open_file *of,
    				    char *buf, size_t nbytes, loff_t off)
    {
    	struct cpuset *cs = css_cs(of_css(of));
    	struct cpuset *trialcs;
    	int retval = -ENODEV;
    
    	buf = strstrip(buf);
    
    	/*
    	 * CPU or memory hotunplug may leave @cs w/o any execution
    	 * resources, in which case the hotplug code asynchronously updates
    	 * configuration and transfers all tasks to the nearest ancestor
    	 * which can execute.
    	 *
    	 * As writes to "cpus" or "mems" may restore @cs's execution
    	 * resources, wait for the previously scheduled operations before
    	 * proceeding, so that we don't end up keep removing tasks added
    	 * after execution capability is restored.
    	 *
    	 * cpuset_hotplug_work calls back into cgroup core via
    	 * cgroup_transfer_tasks() and waiting for it from a cgroupfs
    	 * operation like this one can lead to a deadlock through kernfs
    	 * active_ref protection.  Let's break the protection.  Losing the
    	 * protection is okay as we check whether @cs is online after
    	 * grabbing cpuset_mutex anyway.  This only happens on the legacy
    	 * hierarchies.
    	 */
    	css_get(&cs->css);
    	kernfs_break_active_protection(of->kn);
    	flush_work(&cpuset_hotplug_work);
    
    	mutex_lock(&cpuset_mutex);
    	if (!is_cpuset_online(cs))
    		goto out_unlock;
    
    	trialcs = alloc_trial_cpuset(cs);
    	if (!trialcs) {
    		retval = -ENOMEM;
    		goto out_unlock;
    	}
    
    	switch (of_cft(of)->private) {
    	case FILE_CPULIST:
    		retval = update_cpumask(cs, trialcs, buf);
    		break;
    	case FILE_MEMLIST:
    		retval = update_nodemask(cs, trialcs, buf);
    		break;
    	default:
    		retval = -EINVAL;
    		break;
    	}
    
    	free_trial_cpuset(trialcs);
    out_unlock:
    	mutex_unlock(&cpuset_mutex);
    	kernfs_unbreak_active_protection(of->kn);
    	css_put(&cs->css);
    	flush_workqueue(cpuset_migrate_mm_wq);
    	return retval ?: nbytes;
    }
    
    /*
     * These ascii lists should be read in a single call, by using a user
     * buffer large enough to hold the entire map.  If read in smaller
     * chunks, there is no guarantee of atomicity.  Since the display format
     * used, list of ranges of sequential numbers, is variable length,
     * and since these maps can change value dynamically, one could read
     * gibberish by doing partial reads while a list was changing.
     */
    static int cpuset_common_seq_show(struct seq_file *sf, void *v)
    {
    	struct cpuset *cs = css_cs(seq_css(sf));
    	cpuset_filetype_t type = seq_cft(sf)->private;
    	int ret = 0;
    
    	spin_lock_irq(&callback_lock);
    
    	switch (type) {
    	case FILE_CPULIST:
    		seq_printf(sf, "%*pbl\n", cpumask_pr_args(cs->cpus_allowed));
    		break;
    	case FILE_MEMLIST:
    		seq_printf(sf, "%*pbl\n", nodemask_pr_args(&cs->mems_allowed));
    		break;
    	case FILE_EFFECTIVE_CPULIST:
    		seq_printf(sf, "%*pbl\n", cpumask_pr_args(cs->effective_cpus));
    		break;
    	case FILE_EFFECTIVE_MEMLIST:
    		seq_printf(sf, "%*pbl\n", nodemask_pr_args(&cs->effective_mems));
    		break;
    	default:
    		ret = -EINVAL;
    	}
    
    	spin_unlock_irq(&callback_lock);
    	return ret;
    }
    
    static u64 cpuset_read_u64(struct cgroup_subsys_state *css, struct cftype *cft)
    {
    	struct cpuset *cs = css_cs(css);
    	cpuset_filetype_t type = cft->private;
    	switch (type) {
    	case FILE_CPU_EXCLUSIVE:
    		return is_cpu_exclusive(cs);
    	case FILE_MEM_EXCLUSIVE:
    		return is_mem_exclusive(cs);
    	case FILE_MEM_HARDWALL:
    		return is_mem_hardwall(cs);
    	case FILE_SCHED_LOAD_BALANCE:
    		return is_sched_load_balance(cs);
    	case FILE_MEMORY_MIGRATE:
    		return is_memory_migrate(cs);
    	case FILE_MEMORY_PRESSURE_ENABLED:
    		return cpuset_memory_pressure_enabled;
    	case FILE_MEMORY_PRESSURE:
    		return fmeter_getrate(&cs->fmeter);
    	case FILE_SPREAD_PAGE:
    		return is_spread_page(cs);
    	case FILE_SPREAD_SLAB:
    		return is_spread_slab(cs);
    	default:
    		BUG();
    	}
    
    	/* Unreachable but makes gcc happy */
    	return 0;
    }
    
    static s64 cpuset_read_s64(struct cgroup_subsys_state *css, struct cftype *cft)
    {
    	struct cpuset *cs = css_cs(css);
    	cpuset_filetype_t type = cft->private;
    	switch (type) {
    	case FILE_SCHED_RELAX_DOMAIN_LEVEL:
    		return cs->relax_domain_level;
    	default:
    		BUG();
    	}
    
    	/* Unrechable but makes gcc happy */
    	return 0;
    }
    
    
    /*
     * for the common functions, 'private' gives the type of file
     */
    
    static struct cftype files[] = {
    	{
    		.name = "cpus",
    		.seq_show = cpuset_common_seq_show,
    		.write = cpuset_write_resmask,
    		.max_write_len = (100U + 6 * NR_CPUS),
    		.private = FILE_CPULIST,
    	},
    
    	{
    		.name = "mems",
    		.seq_show = cpuset_common_seq_show,
    		.write = cpuset_write_resmask,
    		.max_write_len = (100U + 6 * MAX_NUMNODES),
    		.private = FILE_MEMLIST,
    	},
    
    	{
    		.name = "effective_cpus",
    		.seq_show = cpuset_common_seq_show,
    		.private = FILE_EFFECTIVE_CPULIST,
    	},
    
    	{
    		.name = "effective_mems",
    		.seq_show = cpuset_common_seq_show,
    		.private = FILE_EFFECTIVE_MEMLIST,
    	},
    
    	{
    		.name = "cpu_exclusive",
    		.read_u64 = cpuset_read_u64,
    		.write_u64 = cpuset_write_u64,
    		.private = FILE_CPU_EXCLUSIVE,
    	},
    
    	{
    		.name = "mem_exclusive",
    		.read_u64 = cpuset_read_u64,
    		.write_u64 = cpuset_write_u64,
    		.private = FILE_MEM_EXCLUSIVE,
    	},
    
    	{
    		.name = "mem_hardwall",
    		.read_u64 = cpuset_read_u64,
    		.write_u64 = cpuset_write_u64,
    		.private = FILE_MEM_HARDWALL,
    	},
    
    	{
    		.name = "sched_load_balance",
    		.read_u64 = cpuset_read_u64,
    		.write_u64 = cpuset_write_u64,
    		.private = FILE_SCHED_LOAD_BALANCE,
    	},
    
    	{
    		.name = "sched_relax_domain_level",
    		.read_s64 = cpuset_read_s64,
    		.write_s64 = cpuset_write_s64,
    		.private = FILE_SCHED_RELAX_DOMAIN_LEVEL,
    	},
    
    	{
    		.name = "memory_migrate",
    		.read_u64 = cpuset_read_u64,
    		.write_u64 = cpuset_write_u64,
    		.private = FILE_MEMORY_MIGRATE,
    	},
    
    	{
    		.name = "memory_pressure",
    		.read_u64 = cpuset_read_u64,
    	},
    
    	{
    		.name = "memory_spread_page",
    		.read_u64 = cpuset_read_u64,
    		.write_u64 = cpuset_write_u64,
    		.private = FILE_SPREAD_PAGE,
    	},
    
    	{
    		.name = "memory_spread_slab",
    		.read_u64 = cpuset_read_u64,
    		.write_u64 = cpuset_write_u64,
    		.private = FILE_SPREAD_SLAB,
    	},
    
    	{
    		.name = "memory_pressure_enabled",
    		.flags = CFTYPE_ONLY_ON_ROOT,
    		.read_u64 = cpuset_read_u64,
    		.write_u64 = cpuset_write_u64,
    		.private = FILE_MEMORY_PRESSURE_ENABLED,
    	},
    
    	{ }	/* terminate */
    };
    
    /*
     *	cpuset_css_alloc - allocate a cpuset css
     *	cgrp:	control group that the new cpuset will be part of
     */
    
    static struct cgroup_subsys_state *
    cpuset_css_alloc(struct cgroup_subsys_state *parent_css)
    {
    	struct cpuset *cs;
    
    	if (!parent_css)
    		return &top_cpuset.css;
    
    	cs = kzalloc(sizeof(*cs), GFP_KERNEL);
    	if (!cs)
    		return ERR_PTR(-ENOMEM);
    	if (!alloc_cpumask_var(&cs->cpus_allowed, GFP_KERNEL))
    		goto free_cs;
    	if (!alloc_cpumask_var(&cs->effective_cpus, GFP_KERNEL))
    		goto free_cpus;
    
    	set_bit(CS_SCHED_LOAD_BALANCE, &cs->flags);
    	cpumask_clear(cs->cpus_allowed);
    	nodes_clear(cs->mems_allowed);
    	cpumask_clear(cs->effective_cpus);
    	nodes_clear(cs->effective_mems);
    	fmeter_init(&cs->fmeter);
    	cs->relax_domain_level = -1;
    
    	return &cs->css;
    
    free_cpus:
    	free_cpumask_var(cs->cpus_allowed);
    free_cs:
    	kfree(cs);
    	return ERR_PTR(-ENOMEM);
    }
    
    static int cpuset_css_online(struct cgroup_subsys_state *css)
    {
    	struct cpuset *cs = css_cs(css);
    	struct cpuset *parent = parent_cs(cs);
    	struct cpuset *tmp_cs;
    	struct cgroup_subsys_state *pos_css;
    
    	if (!parent)
    		return 0;
    
    	mutex_lock(&cpuset_mutex);
    
    	set_bit(CS_ONLINE, &cs->flags);
    	if (is_spread_page(parent))
    		set_bit(CS_SPREAD_PAGE, &cs->flags);
    	if (is_spread_slab(parent))
    		set_bit(CS_SPREAD_SLAB, &cs->flags);
    
    	cpuset_inc();
    
    	spin_lock_irq(&callback_lock);
    	if (cgroup_subsys_on_dfl(cpuset_cgrp_subsys)) {
    		cpumask_copy(cs->effective_cpus, parent->effective_cpus);
    		cs->effective_mems = parent->effective_mems;
    	}
    	spin_unlock_irq(&callback_lock);
    
    	if (!test_bit(CGRP_CPUSET_CLONE_CHILDREN, &css->cgroup->flags))
    		goto out_unlock;
    
    	/*
    	 * Clone @parent's configuration if CGRP_CPUSET_CLONE_CHILDREN is
    	 * set.  This flag handling is implemented in cgroup core for
    	 * histrical reasons - the flag may be specified during mount.
    	 *
    	 * Currently, if any sibling cpusets have exclusive cpus or mem, we
    	 * refuse to clone the configuration - thereby refusing the task to
    	 * be entered, and as a result refusing the sys_unshare() or
    	 * clone() which initiated it.  If this becomes a problem for some
    	 * users who wish to allow that scenario, then this could be
    	 * changed to grant parent->cpus_allowed-sibling_cpus_exclusive
    	 * (and likewise for mems) to the new cgroup.
    	 */
    	rcu_read_lock();
    	cpuset_for_each_child(tmp_cs, pos_css, parent) {
    		if (is_mem_exclusive(tmp_cs) || is_cpu_exclusive(tmp_cs)) {
    			rcu_read_unlock();
    			goto out_unlock;
    		}
    	}
    	rcu_read_unlock();
    
    	spin_lock_irq(&callback_lock);
    	cs->mems_allowed = parent->mems_allowed;
    	cs->effective_mems = parent->mems_allowed;
    	cpumask_copy(cs->cpus_allowed, parent->cpus_allowed);
    	cpumask_copy(cs->effective_cpus, parent->cpus_allowed);
    	spin_unlock_irq(&callback_lock);
    out_unlock:
    	mutex_unlock(&cpuset_mutex);
    	return 0;
    }
    
    /*
     * If the cpuset being removed has its flag 'sched_load_balance'
     * enabled, then simulate turning sched_load_balance off, which
     * will call rebuild_sched_domains_locked().
     */
    
    static void cpuset_css_offline(struct cgroup_subsys_state *css)
    {
    	struct cpuset *cs = css_cs(css);
    
    	mutex_lock(&cpuset_mutex);
    
    	if (is_sched_load_balance(cs))
    		update_flag(CS_SCHED_LOAD_BALANCE, cs, 0);
    
    	cpuset_dec();
    	clear_bit(CS_ONLINE, &cs->flags);
    
    	mutex_unlock(&cpuset_mutex);
    }
    
    static void cpuset_css_free(struct cgroup_subsys_state *css)
    {
    	struct cpuset *cs = css_cs(css);
    
    	free_cpumask_var(cs->effective_cpus);
    	free_cpumask_var(cs->cpus_allowed);
    	kfree(cs);
    }
    
    static void cpuset_bind(struct cgroup_subsys_state *root_css)
    {
    	mutex_lock(&cpuset_mutex);
    	spin_lock_irq(&callback_lock);
    
    	if (cgroup_subsys_on_dfl(cpuset_cgrp_subsys)) {
    		cpumask_copy(top_cpuset.cpus_allowed, cpu_possible_mask);
    		top_cpuset.mems_allowed = node_possible_map;
    	} else {
    		cpumask_copy(top_cpuset.cpus_allowed,
    			     top_cpuset.effective_cpus);
    		top_cpuset.mems_allowed = top_cpuset.effective_mems;
    	}
    
    	spin_unlock_irq(&callback_lock);
    	mutex_unlock(&cpuset_mutex);
    }
    
    struct cgroup_subsys cpuset_cgrp_subsys = {
    	.css_alloc	= cpuset_css_alloc,
    	.css_online	= cpuset_css_online,
    	.css_offline	= cpuset_css_offline,
    	.css_free	= cpuset_css_free,
    	.can_attach	= cpuset_can_attach,
    	.cancel_attach	= cpuset_cancel_attach,
    	.attach		= cpuset_attach,
    	.post_attach	= cpuset_post_attach,
    	.bind		= cpuset_bind,
    	.legacy_cftypes	= files,
    	.early_init	= true,
    };
    
    /**
     * cpuset_init - initialize cpusets at system boot
     *
     * Description: Initialize top_cpuset and the cpuset internal file system,
     **/
    
    int __init cpuset_init(void)
    {
    	int err = 0;
    
    	if (!alloc_cpumask_var(&top_cpuset.cpus_allowed, GFP_KERNEL))
    		BUG();
    	if (!alloc_cpumask_var(&top_cpuset.effective_cpus, GFP_KERNEL))
    		BUG();
    
    	cpumask_setall(top_cpuset.cpus_allowed);
    	nodes_setall(top_cpuset.mems_allowed);
    	cpumask_setall(top_cpuset.effective_cpus);
    	nodes_setall(top_cpuset.effective_mems);
    
    	fmeter_init(&top_cpuset.fmeter);
    	set_bit(CS_SCHED_LOAD_BALANCE, &top_cpuset.flags);
    	top_cpuset.relax_domain_level = -1;
    
    	err = register_filesystem(&cpuset_fs_type);
    	if (err < 0)
    		return err;
    
    	if (!alloc_cpumask_var(&cpus_attach, GFP_KERNEL))
    		BUG();
    
    	return 0;
    }
    
    /*
     * If CPU and/or memory hotplug handlers, below, unplug any CPUs
     * or memory nodes, we need to walk over the cpuset hierarchy,
     * removing that CPU or node from all cpusets.  If this removes the
     * last CPU or node from a cpuset, then move the tasks in the empty
     * cpuset to its next-highest non-empty parent.
     */
    static void remove_tasks_in_empty_cpuset(struct cpuset *cs)
    {
    	struct cpuset *parent;
    
    	/*
    	 * Find its next-highest non-empty parent, (top cpuset
    	 * has online cpus, so can't be empty).
    	 */
    	parent = parent_cs(cs);
    	while (cpumask_empty(parent->cpus_allowed) ||
    			nodes_empty(parent->mems_allowed))
    		parent = parent_cs(parent);
    
    	if (cgroup_transfer_tasks(parent->css.cgroup, cs->css.cgroup)) {
    		pr_err("cpuset: failed to transfer tasks out of empty cpuset ");
    		pr_cont_cgroup_name(cs->css.cgroup);
    		pr_cont("\n");
    	}
    }
    
    static void
    hotplug_update_tasks_legacy(struct cpuset *cs,
    			    struct cpumask *new_cpus, nodemask_t *new_mems,
    			    bool cpus_updated, bool mems_updated)
    {
    	bool is_empty;
    
    	spin_lock_irq(&callback_lock);
    	cpumask_copy(cs->cpus_allowed, new_cpus);
    	cpumask_copy(cs->effective_cpus, new_cpus);
    	cs->mems_allowed = *new_mems;
    	cs->effective_mems = *new_mems;
    	spin_unlock_irq(&callback_lock);
    
    	/*
    	 * Don't call update_tasks_cpumask() if the cpuset becomes empty,
    	 * as the tasks will be migratecd to an ancestor.
    	 */
    	if (cpus_updated && !cpumask_empty(cs->cpus_allowed))
    		update_tasks_cpumask(cs);
    	if (mems_updated && !nodes_empty(cs->mems_allowed))
    		update_tasks_nodemask(cs);
    
    	is_empty = cpumask_empty(cs->cpus_allowed) ||
    		   nodes_empty(cs->mems_allowed);
    
    	mutex_unlock(&cpuset_mutex);
    
    	/*
    	 * Move tasks to the nearest ancestor with execution resources,
    	 * This is full cgroup operation which will also call back into
    	 * cpuset. Should be done outside any lock.
    	 */
    	if (is_empty)
    		remove_tasks_in_empty_cpuset(cs);
    
    	mutex_lock(&cpuset_mutex);
    }
    
    static void
    hotplug_update_tasks(struct cpuset *cs,
    		     struct cpumask *new_cpus, nodemask_t *new_mems,
    		     bool cpus_updated, bool mems_updated)
    {
    	if (cpumask_empty(new_cpus))
    		cpumask_copy(new_cpus, parent_cs(cs)->effective_cpus);
    	if (nodes_empty(*new_mems))
    		*new_mems = parent_cs(cs)->effective_mems;
    
    	spin_lock_irq(&callback_lock);
    	cpumask_copy(cs->effective_cpus, new_cpus);
    	cs->effective_mems = *new_mems;
    	spin_unlock_irq(&callback_lock);
    
    	if (cpus_updated)
    		update_tasks_cpumask(cs);
    	if (mems_updated)
    		update_tasks_nodemask(cs);
    }
    
    /**
     * cpuset_hotplug_update_tasks - update tasks in a cpuset for hotunplug
     * @cs: cpuset in interest
     *
     * Compare @cs's cpu and mem masks against top_cpuset and if some have gone
     * offline, update @cs accordingly.  If @cs ends up with no CPU or memory,
     * all its tasks are moved to the nearest ancestor with both resources.
     */
    static void cpuset_hotplug_update_tasks(struct cpuset *cs)
    {
    	static cpumask_t new_cpus;
    	static nodemask_t new_mems;
    	bool cpus_updated;
    	bool mems_updated;
    retry:
    	wait_event(cpuset_attach_wq, cs->attach_in_progress == 0);
    
    	mutex_lock(&cpuset_mutex);
    
    	/*
    	 * We have raced with task attaching. We wait until attaching
    	 * is finished, so we won't attach a task to an empty cpuset.
    	 */
    	if (cs->attach_in_progress) {
    		mutex_unlock(&cpuset_mutex);
    		goto retry;
    	}
    
    	cpumask_and(&new_cpus, cs->cpus_allowed, parent_cs(cs)->effective_cpus);
    	nodes_and(new_mems, cs->mems_allowed, parent_cs(cs)->effective_mems);
    
    	cpus_updated = !cpumask_equal(&new_cpus, cs->effective_cpus);
    	mems_updated = !nodes_equal(new_mems, cs->effective_mems);
    
    	if (cgroup_subsys_on_dfl(cpuset_cgrp_subsys))
    		hotplug_update_tasks(cs, &new_cpus, &new_mems,
    				     cpus_updated, mems_updated);
    	else
    		hotplug_update_tasks_legacy(cs, &new_cpus, &new_mems,
    					    cpus_updated, mems_updated);
    
    	mutex_unlock(&cpuset_mutex);
    }
    
    /**
     * cpuset_hotplug_workfn - handle CPU/memory hotunplug for a cpuset
     *
     * This function is called after either CPU or memory configuration has
     * changed and updates cpuset accordingly.  The top_cpuset is always
     * synchronized to cpu_active_mask and N_MEMORY, which is necessary in
     * order to make cpusets transparent (of no affect) on systems that are
     * actively using CPU hotplug but making no active use of cpusets.
     *
     * Non-root cpusets are only affected by offlining.  If any CPUs or memory
     * nodes have been taken down, cpuset_hotplug_update_tasks() is invoked on
     * all descendants.
     *
     * Note that CPU offlining during suspend is ignored.  We don't modify
     * cpusets across suspend/resume cycles at all.
     */
    static void cpuset_hotplug_workfn(struct work_struct *work)
    {
    	static cpumask_t new_cpus;
    	static nodemask_t new_mems;
    	bool cpus_updated, mems_updated;
    	bool on_dfl = cgroup_subsys_on_dfl(cpuset_cgrp_subsys);
    
    	mutex_lock(&cpuset_mutex);
    
    	/* fetch the available cpus/mems and find out which changed how */
    	cpumask_copy(&new_cpus, cpu_active_mask);
    	new_mems = node_states[N_MEMORY];
    
    	cpus_updated = !cpumask_equal(top_cpuset.effective_cpus, &new_cpus);
    	mems_updated = !nodes_equal(top_cpuset.effective_mems, new_mems);
    
    	/* synchronize cpus_allowed to cpu_active_mask */
    	if (cpus_updated) {
    		spin_lock_irq(&callback_lock);
    		if (!on_dfl)
    			cpumask_copy(top_cpuset.cpus_allowed, &new_cpus);
    		cpumask_copy(top_cpuset.effective_cpus, &new_cpus);
    		spin_unlock_irq(&callback_lock);
    		/* we don't mess with cpumasks of tasks in top_cpuset */
    	}
    
    	/* synchronize mems_allowed to N_MEMORY */
    	if (mems_updated) {
    		spin_lock_irq(&callback_lock);
    		if (!on_dfl)
    			top_cpuset.mems_allowed = new_mems;
    		top_cpuset.effective_mems = new_mems;
    		spin_unlock_irq(&callback_lock);
    		update_tasks_nodemask(&top_cpuset);
    	}
    
    	mutex_unlock(&cpuset_mutex);
    
    	/* if cpus or mems changed, we need to propagate to descendants */
    	if (cpus_updated || mems_updated) {
    		struct cpuset *cs;
    		struct cgroup_subsys_state *pos_css;
    
    		rcu_read_lock();
    		cpuset_for_each_descendant_pre(cs, pos_css, &top_cpuset) {
    			if (cs == &top_cpuset || !css_tryget_online(&cs->css))
    				continue;
    			rcu_read_unlock();
    
    			cpuset_hotplug_update_tasks(cs);
    
    			rcu_read_lock();
    			css_put(&cs->css);
    		}
    		rcu_read_unlock();
    	}
    
    	/* rebuild sched domains if cpus_allowed has changed */
    	if (cpus_updated)
    		rebuild_sched_domains();
    }
    
    void cpuset_update_active_cpus(bool cpu_online)
    {
    	/*
    	 * We're inside cpu hotplug critical region which usually nests
    	 * inside cgroup synchronization.  Bounce actual hotplug processing
    	 * to a work item to avoid reverse locking order.
    	 *
    	 * We still need to do partition_sched_domains() synchronously;
    	 * otherwise, the scheduler will get confused and put tasks to the
    	 * dead CPU.  Fall back to the default single domain.
    	 * cpuset_hotplug_workfn() will rebuild it as necessary.
    	 */
    	partition_sched_domains(1, NULL, NULL);
    	schedule_work(&cpuset_hotplug_work);
    }
    
    /*
     * Keep top_cpuset.mems_allowed tracking node_states[N_MEMORY].
     * Call this routine anytime after node_states[N_MEMORY] changes.
     * See cpuset_update_active_cpus() for CPU hotplug handling.
     */
    static int cpuset_track_online_nodes(struct notifier_block *self,
    				unsigned long action, void *arg)
    {
    	schedule_work(&cpuset_hotplug_work);
    	return NOTIFY_OK;
    }
    
    static struct notifier_block cpuset_track_online_nodes_nb = {
    	.notifier_call = cpuset_track_online_nodes,
    	.priority = 10,		/* ??! */
    };
    
    /**
     * cpuset_init_smp - initialize cpus_allowed
     *
     * Description: Finish top cpuset after cpu, node maps are initialized
     */
    void __init cpuset_init_smp(void)
    {
    	cpumask_copy(top_cpuset.cpus_allowed, cpu_active_mask);
    	top_cpuset.mems_allowed = node_states[N_MEMORY];
    	top_cpuset.old_mems_allowed = top_cpuset.mems_allowed;
    
    	cpumask_copy(top_cpuset.effective_cpus, cpu_active_mask);
    	top_cpuset.effective_mems = node_states[N_MEMORY];
    
    	register_hotmemory_notifier(&cpuset_track_online_nodes_nb);
    
    	cpuset_migrate_mm_wq = alloc_ordered_workqueue("cpuset_migrate_mm", 0);
    	BUG_ON(!cpuset_migrate_mm_wq);
    }
    
    /**
     * cpuset_cpus_allowed - return cpus_allowed mask from a tasks cpuset.
     * @tsk: pointer to task_struct from which to obtain cpuset->cpus_allowed.
     * @pmask: pointer to struct cpumask variable to receive cpus_allowed set.
     *
     * Description: Returns the cpumask_var_t cpus_allowed of the cpuset
     * attached to the specified @tsk.  Guaranteed to return some non-empty
     * subset of cpu_online_mask, even if this means going outside the
     * tasks cpuset.
     **/
    
    void cpuset_cpus_allowed(struct task_struct *tsk, struct cpumask *pmask)
    {
    	unsigned long flags;
    
    	spin_lock_irqsave(&callback_lock, flags);
    	rcu_read_lock();
    	guarantee_online_cpus(task_cs(tsk), pmask);
    	rcu_read_unlock();
    	spin_unlock_irqrestore(&callback_lock, flags);
    }
    
    void cpuset_cpus_allowed_fallback(struct task_struct *tsk)
    {
    	rcu_read_lock();
    	do_set_cpus_allowed(tsk, task_cs(tsk)->effective_cpus);
    	rcu_read_unlock();
    
    	/*
    	 * We own tsk->cpus_allowed, nobody can change it under us.
    	 *
    	 * But we used cs && cs->cpus_allowed lockless and thus can
    	 * race with cgroup_attach_task() or update_cpumask() and get
    	 * the wrong tsk->cpus_allowed. However, both cases imply the
    	 * subsequent cpuset_change_cpumask()->set_cpus_allowed_ptr()
    	 * which takes task_rq_lock().
    	 *
    	 * If we are called after it dropped the lock we must see all
    	 * changes in tsk_cs()->cpus_allowed. Otherwise we can temporary
    	 * set any mask even if it is not right from task_cs() pov,
    	 * the pending set_cpus_allowed_ptr() will fix things.
    	 *
    	 * select_fallback_rq() will fix things ups and set cpu_possible_mask
    	 * if required.
    	 */
    }
    
    void __init cpuset_init_current_mems_allowed(void)
    {
    	nodes_setall(current->mems_allowed);
    }
    
    /**
     * cpuset_mems_allowed - return mems_allowed mask from a tasks cpuset.
     * @tsk: pointer to task_struct from which to obtain cpuset->mems_allowed.
     *
     * Description: Returns the nodemask_t mems_allowed of the cpuset
     * attached to the specified @tsk.  Guaranteed to return some non-empty
     * subset of node_states[N_MEMORY], even if this means going outside the
     * tasks cpuset.
     **/
    
    nodemask_t cpuset_mems_allowed(struct task_struct *tsk)
    {
    	nodemask_t mask;
    	unsigned long flags;
    
    	spin_lock_irqsave(&callback_lock, flags);
    	rcu_read_lock();
    	guarantee_online_mems(task_cs(tsk), &mask);
    	rcu_read_unlock();
    	spin_unlock_irqrestore(&callback_lock, flags);
    
    	return mask;
    }
    
    /**
     * cpuset_nodemask_valid_mems_allowed - check nodemask vs. curremt mems_allowed
     * @nodemask: the nodemask to be checked
     *
     * Are any of the nodes in the nodemask allowed in current->mems_allowed?
     */
    int cpuset_nodemask_valid_mems_allowed(nodemask_t *nodemask)
    {
    	return nodes_intersects(*nodemask, current->mems_allowed);
    }
    
    /*
     * nearest_hardwall_ancestor() - Returns the nearest mem_exclusive or
     * mem_hardwall ancestor to the specified cpuset.  Call holding
     * callback_lock.  If no ancestor is mem_exclusive or mem_hardwall
     * (an unusual configuration), then returns the root cpuset.
     */
    static struct cpuset *nearest_hardwall_ancestor(struct cpuset *cs)
    {
    	while (!(is_mem_exclusive(cs) || is_mem_hardwall(cs)) && parent_cs(cs))
    		cs = parent_cs(cs);
    	return cs;
    }
    
    /**
     * cpuset_node_allowed - Can we allocate on a memory node?
     * @node: is this an allowed node?
     * @gfp_mask: memory allocation flags
     *
     * If we're in interrupt, yes, we can always allocate.  If @node is set in
     * current's mems_allowed, yes.  If it's not a __GFP_HARDWALL request and this
     * node is set in the nearest hardwalled cpuset ancestor to current's cpuset,
     * yes.  If current has access to memory reserves due to TIF_MEMDIE, yes.
     * Otherwise, no.
     *
     * GFP_USER allocations are marked with the __GFP_HARDWALL bit,
     * and do not allow allocations outside the current tasks cpuset
     * unless the task has been OOM killed as is marked TIF_MEMDIE.
     * GFP_KERNEL allocations are not so marked, so can escape to the
     * nearest enclosing hardwalled ancestor cpuset.
     *
     * Scanning up parent cpusets requires callback_lock.  The
     * __alloc_pages() routine only calls here with __GFP_HARDWALL bit
     * _not_ set if it's a GFP_KERNEL allocation, and all nodes in the
     * current tasks mems_allowed came up empty on the first pass over
     * the zonelist.  So only GFP_KERNEL allocations, if all nodes in the
     * cpuset are short of memory, might require taking the callback_lock.
     *
     * The first call here from mm/page_alloc:get_page_from_freelist()
     * has __GFP_HARDWALL set in gfp_mask, enforcing hardwall cpusets,
     * so no allocation on a node outside the cpuset is allowed (unless
     * in interrupt, of course).
     *
     * The second pass through get_page_from_freelist() doesn't even call
     * here for GFP_ATOMIC calls.  For those calls, the __alloc_pages()
     * variable 'wait' is not set, and the bit ALLOC_CPUSET is not set
     * in alloc_flags.  That logic and the checks below have the combined
     * affect that:
     *	in_interrupt - any node ok (current task context irrelevant)
     *	GFP_ATOMIC   - any node ok
     *	TIF_MEMDIE   - any node ok
     *	GFP_KERNEL   - any node in enclosing hardwalled cpuset ok
     *	GFP_USER     - only nodes in current tasks mems allowed ok.
     */
    bool __cpuset_node_allowed(int node, gfp_t gfp_mask)
    {
    	struct cpuset *cs;		/* current cpuset ancestors */
    	int allowed;			/* is allocation in zone z allowed? */
    	unsigned long flags;
    
    	if (in_interrupt())
    		return true;
    	if (node_isset(node, current->mems_allowed))
    		return true;
    	/*
    	 * Allow tasks that have access to memory reserves because they have
    	 * been OOM killed to get memory anywhere.
    	 */
    	if (unlikely(test_thread_flag(TIF_MEMDIE)))
    		return true;
    	if (gfp_mask & __GFP_HARDWALL)	/* If hardwall request, stop here */
    		return false;
    
    	if (current->flags & PF_EXITING) /* Let dying task have memory */
    		return true;
    
    	/* Not hardwall and node outside mems_allowed: scan up cpusets */
    	spin_lock_irqsave(&callback_lock, flags);
    
    	rcu_read_lock();
    	cs = nearest_hardwall_ancestor(task_cs(current));
    	allowed = node_isset(node, cs->mems_allowed);
    	rcu_read_unlock();
    
    	spin_unlock_irqrestore(&callback_lock, flags);
    	return allowed;
    }
    
    /**
     * cpuset_mem_spread_node() - On which node to begin search for a file page
     * cpuset_slab_spread_node() - On which node to begin search for a slab page
     *
     * If a task is marked PF_SPREAD_PAGE or PF_SPREAD_SLAB (as for
     * tasks in a cpuset with is_spread_page or is_spread_slab set),
     * and if the memory allocation used cpuset_mem_spread_node()
     * to determine on which node to start looking, as it will for
     * certain page cache or slab cache pages such as used for file
     * system buffers and inode caches, then instead of starting on the
     * local node to look for a free page, rather spread the starting
     * node around the tasks mems_allowed nodes.
     *
     * We don't have to worry about the returned node being offline
     * because "it can't happen", and even if it did, it would be ok.
     *
     * The routines calling guarantee_online_mems() are careful to
     * only set nodes in task->mems_allowed that are online.  So it
     * should not be possible for the following code to return an
     * offline node.  But if it did, that would be ok, as this routine
     * is not returning the node where the allocation must be, only
     * the node where the search should start.  The zonelist passed to
     * __alloc_pages() will include all nodes.  If the slab allocator
     * is passed an offline node, it will fall back to the local node.
     * See kmem_cache_alloc_node().
     */
    
    static int cpuset_spread_node(int *rotor)
    {
    	return *rotor = next_node_in(*rotor, current->mems_allowed);
    }
    
    int cpuset_mem_spread_node(void)
    {
    	if (current->cpuset_mem_spread_rotor == NUMA_NO_NODE)
    		current->cpuset_mem_spread_rotor =
    			node_random(&current->mems_allowed);
    
    	return cpuset_spread_node(&current->cpuset_mem_spread_rotor);
    }
    
    int cpuset_slab_spread_node(void)
    {
    	if (current->cpuset_slab_spread_rotor == NUMA_NO_NODE)
    		current->cpuset_slab_spread_rotor =
    			node_random(&current->mems_allowed);
    
    	return cpuset_spread_node(&current->cpuset_slab_spread_rotor);
    }
    
    EXPORT_SYMBOL_GPL(cpuset_mem_spread_node);
    
    /**
     * cpuset_mems_allowed_intersects - Does @tsk1's mems_allowed intersect @tsk2's?
     * @tsk1: pointer to task_struct of some task.
     * @tsk2: pointer to task_struct of some other task.
     *
     * Description: Return true if @tsk1's mems_allowed intersects the
     * mems_allowed of @tsk2.  Used by the OOM killer to determine if
     * one of the task's memory usage might impact the memory available
     * to the other.
     **/
    
    int cpuset_mems_allowed_intersects(const struct task_struct *tsk1,
    				   const struct task_struct *tsk2)
    {
    	return nodes_intersects(tsk1->mems_allowed, tsk2->mems_allowed);
    }
    
    /**
     * cpuset_print_current_mems_allowed - prints current's cpuset and mems_allowed
     *
     * Description: Prints current's name, cpuset name, and cached copy of its
     * mems_allowed to the kernel log.
     */
    void cpuset_print_current_mems_allowed(void)
    {
    	struct cgroup *cgrp;
    
    	rcu_read_lock();
    
    	cgrp = task_cs(current)->css.cgroup;
    	pr_info("%s cpuset=", current->comm);
    	pr_cont_cgroup_name(cgrp);
    	pr_cont(" mems_allowed=%*pbl\n",
    		nodemask_pr_args(&current->mems_allowed));
    
    	rcu_read_unlock();
    }
    
    /*
     * Collection of memory_pressure is suppressed unless
     * this flag is enabled by writing "1" to the special
     * cpuset file 'memory_pressure_enabled' in the root cpuset.
     */
    
    int cpuset_memory_pressure_enabled __read_mostly;
    
    /**
     * cpuset_memory_pressure_bump - keep stats of per-cpuset reclaims.
     *
     * Keep a running average of the rate of synchronous (direct)
     * page reclaim efforts initiated by tasks in each cpuset.
     *
     * This represents the rate at which some task in the cpuset
     * ran low on memory on all nodes it was allowed to use, and
     * had to enter the kernels page reclaim code in an effort to
     * create more free memory by tossing clean pages or swapping
     * or writing dirty pages.
     *
     * Display to user space in the per-cpuset read-only file
     * "memory_pressure".  Value displayed is an integer
     * representing the recent rate of entry into the synchronous
     * (direct) page reclaim by any task attached to the cpuset.
     **/
    
    void __cpuset_memory_pressure_bump(void)
    {
    	rcu_read_lock();
    	fmeter_markevent(&task_cs(current)->fmeter);
    	rcu_read_unlock();
    }
    
    #ifdef CONFIG_PROC_PID_CPUSET
    /*
     * proc_cpuset_show()
     *  - Print tasks cpuset path into seq_file.
     *  - Used for /proc/<pid>/cpuset.
     *  - No need to task_lock(tsk) on this tsk->cpuset reference, as it
     *    doesn't really matter if tsk->cpuset changes after we read it,
     *    and we take cpuset_mutex, keeping cpuset_attach() from changing it
     *    anyway.
     */
    int proc_cpuset_show(struct seq_file *m, struct pid_namespace *ns,
    		     struct pid *pid, struct task_struct *tsk)
    {
    	char *buf, *p;
    	struct cgroup_subsys_state *css;
    	int retval;
    
    	retval = -ENOMEM;
    	buf = kmalloc(PATH_MAX, GFP_KERNEL);
    	if (!buf)
    		goto out;
    
    	retval = -ENAMETOOLONG;
    	css = task_get_css(tsk, cpuset_cgrp_id);
    	p = cgroup_path_ns(css->cgroup, buf, PATH_MAX,
    			   current->nsproxy->cgroup_ns);
    	css_put(css);
    	if (!p)
    		goto out_free;
    	seq_puts(m, p);
    	seq_putc(m, '\n');
    	retval = 0;
    out_free:
    	kfree(buf);
    out:
    	return retval;
    }
    #endif /* CONFIG_PROC_PID_CPUSET */
    
    /* Display task mems_allowed in /proc/<pid>/status file. */
    void cpuset_task_status_allowed(struct seq_file *m, struct task_struct *task)
    {
    	seq_printf(m, "Mems_allowed:\t%*pb\n",
    		   nodemask_pr_args(&task->mems_allowed));
    	seq_printf(m, "Mems_allowed_list:\t%*pbl\n",
    		   nodemask_pr_args(&task->mems_allowed));
    }