cpuset.c 76.8 KB
Newer Older
Linus Torvalds's avatar
Linus Torvalds committed
1 2 3 4 5 6
/*
 *  kernel/cpuset.c
 *
 *  Processor and Memory placement constraints for sets of tasks.
 *
 *  Copyright (C) 2003 BULL SA.
Paul Jackson's avatar
Paul Jackson committed
7
 *  Copyright (C) 2004-2007 Silicon Graphics, Inc.
8
 *  Copyright (C) 2006 Google, Inc
Linus Torvalds's avatar
Linus Torvalds committed
9 10 11 12
 *
 *  Portions derived from Patrick Mochel's sysfs code.
 *  sysfs is Copyright (c) 2001-3 Patrick Mochel
 *
13
 *  2003-10-10 Written by Simon Derr.
Linus Torvalds's avatar
Linus Torvalds committed
14
 *  2003-10-22 Updates by Stephen Hemminger.
15
 *  2004 May-July Rework by Paul Jackson.
16
 *  2006 Rework by Paul Menage to use generic cgroups
17 18
 *  2008 Rework of the scheduler domains and CPU hotplug handling
 *       by Max Krasnyansky
Linus Torvalds's avatar
Linus Torvalds committed
19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36
 *
 *  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>
37
#include <linux/mempolicy.h>
Linus Torvalds's avatar
Linus Torvalds committed
38
#include <linux/mm.h>
39
#include <linux/memory.h>
40
#include <linux/export.h>
Linus Torvalds's avatar
Linus Torvalds committed
41 42 43 44
#include <linux/mount.h>
#include <linux/namei.h>
#include <linux/pagemap.h>
#include <linux/proc_fs.h>
45
#include <linux/rcupdate.h>
Linus Torvalds's avatar
Linus Torvalds committed
46 47
#include <linux/sched.h>
#include <linux/seq_file.h>
48
#include <linux/security.h>
Linus Torvalds's avatar
Linus Torvalds committed
49 50 51 52 53 54 55 56 57
#include <linux/slab.h>
#include <linux/spinlock.h>
#include <linux/stat.h>
#include <linux/string.h>
#include <linux/time.h>
#include <linux/backing-dev.h>
#include <linux/sort.h>

#include <asm/uaccess.h>
Arun Sharma's avatar
Arun Sharma committed
58
#include <linux/atomic.h>
59
#include <linux/mutex.h>
60 61
#include <linux/workqueue.h>
#include <linux/cgroup.h>
62
#include <linux/wait.h>
Linus Torvalds's avatar
Linus Torvalds committed
63

64
struct static_key cpusets_enabled_key __read_mostly = STATIC_KEY_INIT_FALSE;
65

66 67 68 69 70 71 72 73 74
/* See "Frequency meter" comments, below. */

struct fmeter {
	int cnt;		/* unprocessed events count */
	int val;		/* most recent output value */
	time_t time;		/* clock (secs) when val computed */
	spinlock_t lock;	/* guards read or write of above */
};

Linus Torvalds's avatar
Linus Torvalds committed
75
struct cpuset {
76 77
	struct cgroup_subsys_state css;

Linus Torvalds's avatar
Linus Torvalds committed
78
	unsigned long flags;		/* "unsigned long" so bitops work */
79

80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99
	/*
	 * 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.
	 */

100 101 102 103 104 105 106
	/* 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;
Linus Torvalds's avatar
Linus Torvalds committed
107

108 109 110 111 112 113 114 115 116 117 118 119
	/*
	 * 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;

120
	struct fmeter fmeter;		/* memory_pressure filter */
Paul Jackson's avatar
Paul Jackson committed
121

122 123 124 125 126 127
	/*
	 * Tasks are being attached to this cpuset.  Used to prevent
	 * zeroing cpus/mems_allowed between ->can_attach() and ->attach().
	 */
	int attach_in_progress;

Paul Jackson's avatar
Paul Jackson committed
128 129
	/* partition number for rebuild_sched_domains() */
	int pn;
130

131 132
	/* for custom sched domain */
	int relax_domain_level;
Linus Torvalds's avatar
Linus Torvalds committed
133 134
};

135
static inline struct cpuset *css_cs(struct cgroup_subsys_state *css)
136
{
137
	return css ? container_of(css, struct cpuset, css) : NULL;
138 139 140 141 142
}

/* Retrieve the cpuset for a task */
static inline struct cpuset *task_cs(struct task_struct *task)
{
143
	return css_cs(task_css(task, cpuset_cgrp_id));
144 145
}

146
static inline struct cpuset *parent_cs(struct cpuset *cs)
Tejun Heo's avatar
Tejun Heo committed
147
{
Tejun Heo's avatar
Tejun Heo committed
148
	return css_cs(cs->css.parent);
Tejun Heo's avatar
Tejun Heo committed
149 150
}

151 152 153 154 155 156 157 158 159 160 161 162 163
#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


Linus Torvalds's avatar
Linus Torvalds committed
164 165
/* bits in struct cpuset flags field */
typedef enum {
Tejun Heo's avatar
Tejun Heo committed
166
	CS_ONLINE,
Linus Torvalds's avatar
Linus Torvalds committed
167 168
	CS_CPU_EXCLUSIVE,
	CS_MEM_EXCLUSIVE,
169
	CS_MEM_HARDWALL,
170
	CS_MEMORY_MIGRATE,
Paul Jackson's avatar
Paul Jackson committed
171
	CS_SCHED_LOAD_BALANCE,
172 173
	CS_SPREAD_PAGE,
	CS_SPREAD_SLAB,
Linus Torvalds's avatar
Linus Torvalds committed
174 175 176
} cpuset_flagbits_t;

/* convenient tests for these bits */
Tejun Heo's avatar
Tejun Heo committed
177 178 179 180 181
static inline bool is_cpuset_online(const struct cpuset *cs)
{
	return test_bit(CS_ONLINE, &cs->flags);
}

Linus Torvalds's avatar
Linus Torvalds committed
182 183
static inline int is_cpu_exclusive(const struct cpuset *cs)
{
184
	return test_bit(CS_CPU_EXCLUSIVE, &cs->flags);
Linus Torvalds's avatar
Linus Torvalds committed
185 186 187 188
}

static inline int is_mem_exclusive(const struct cpuset *cs)
{
189
	return test_bit(CS_MEM_EXCLUSIVE, &cs->flags);
Linus Torvalds's avatar
Linus Torvalds committed
190 191
}

192 193 194 195 196
static inline int is_mem_hardwall(const struct cpuset *cs)
{
	return test_bit(CS_MEM_HARDWALL, &cs->flags);
}

Paul Jackson's avatar
Paul Jackson committed
197 198 199 200 201
static inline int is_sched_load_balance(const struct cpuset *cs)
{
	return test_bit(CS_SCHED_LOAD_BALANCE, &cs->flags);
}

202 203
static inline int is_memory_migrate(const struct cpuset *cs)
{
204
	return test_bit(CS_MEMORY_MIGRATE, &cs->flags);
205 206
}

207 208 209 210 211 212 213 214 215 216
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);
}

Linus Torvalds's avatar
Linus Torvalds committed
217
static struct cpuset top_cpuset = {
Tejun Heo's avatar
Tejun Heo committed
218 219
	.flags = ((1 << CS_ONLINE) | (1 << CS_CPU_EXCLUSIVE) |
		  (1 << CS_MEM_EXCLUSIVE)),
Linus Torvalds's avatar
Linus Torvalds committed
220 221
};

222 223 224
/**
 * cpuset_for_each_child - traverse online children of a cpuset
 * @child_cs: loop cursor pointing to the current child
225
 * @pos_css: used for iteration
226 227 228 229 230
 * @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.
 */
231 232 233
#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)))))
234

235 236 237
/**
 * cpuset_for_each_descendant_pre - pre-order walk of a cpuset's descendants
 * @des_cs: loop cursor pointing to the current descendant
238
 * @pos_css: used for iteration
239 240 241
 * @root_cs: target cpuset to walk ancestor of
 *
 * Walk @des_cs through the online descendants of @root_cs.  Must be used
242
 * with RCU read locked.  The caller may modify @pos_css by calling
243 244
 * css_rightmost_descendant() to skip subtree.  @root_cs is included in the
 * iteration and the first node to be visited.
245
 */
246 247 248
#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)))))
249

Linus Torvalds's avatar
Linus Torvalds committed
250
/*
251 252 253 254 255 256 257 258 259 260 261 262 263 264
 * There are two global mutexes guarding cpuset structures - cpuset_mutex
 * and callback_mutex.  The latter may nest inside the former.  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 mutexes 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_mutex 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_mutex to query cpusets.
 * Once it is ready to make the changes, it takes callback_mutex, blocking
 * everyone else.
265 266
 *
 * Calls to the kernel memory allocator can not be made while holding
267
 * callback_mutex, as that would risk double tripping on callback_mutex
268 269 270
 * from one of the callbacks into the cpuset code from within
 * __alloc_pages().
 *
271
 * If a task is only holding callback_mutex, then it has read-only
272 273
 * access to cpusets.
 *
274 275 276
 * 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.
277
 *
278
 * The cpuset_common_file_read() handlers only hold callback_mutex across
279 280 281
 * small pieces of code, such as when reading out possibly multi-word
 * cpumasks and nodemasks.
 *
282 283
 * Accessing a task's cpuset should be done in accordance with the
 * guidelines for accessing subsystem state in kernel/cgroup.c
Linus Torvalds's avatar
Linus Torvalds committed
284 285
 */

286
static DEFINE_MUTEX(cpuset_mutex);
287
static DEFINE_MUTEX(callback_mutex);
288

289 290 291 292 293 294
/*
 * CPU / memory hotplug is handled asynchronously.
 */
static void cpuset_hotplug_workfn(struct work_struct *work);
static DECLARE_WORK(cpuset_hotplug_work, cpuset_hotplug_workfn);

295 296
static DECLARE_WAIT_QUEUE_HEAD(cpuset_attach_wq);

297 298
/*
 * This is ugly, but preserves the userspace API for existing cpuset
299
 * users. If someone tries to mount the "cpuset" filesystem, we
300 301
 * silently switch it to mount "cgroup" instead
 */
Al Viro's avatar
Al Viro committed
302 303
static struct dentry *cpuset_mount(struct file_system_type *fs_type,
			 int flags, const char *unused_dev_name, void *data)
Linus Torvalds's avatar
Linus Torvalds committed
304
{
305
	struct file_system_type *cgroup_fs = get_fs_type("cgroup");
Al Viro's avatar
Al Viro committed
306
	struct dentry *ret = ERR_PTR(-ENODEV);
307 308 309 310
	if (cgroup_fs) {
		char mountopts[] =
			"cpuset,noprefix,"
			"release_agent=/sbin/cpuset_release_agent";
Al Viro's avatar
Al Viro committed
311 312
		ret = cgroup_fs->mount(cgroup_fs, flags,
					   unused_dev_name, mountopts);
313 314 315
		put_filesystem(cgroup_fs);
	}
	return ret;
Linus Torvalds's avatar
Linus Torvalds committed
316 317 318 319
}

static struct file_system_type cpuset_fs_type = {
	.name = "cpuset",
Al Viro's avatar
Al Viro committed
320
	.mount = cpuset_mount,
Linus Torvalds's avatar
Linus Torvalds committed
321 322 323
};

/*
324
 * Return in pmask the portion of a cpusets's cpus_allowed that
Linus Torvalds's avatar
Linus Torvalds committed
325
 * are online.  If none are online, walk up the cpuset hierarchy
326 327
 * until we find one that does have some online cpus.  The top
 * cpuset always has some cpus online.
Linus Torvalds's avatar
Linus Torvalds committed
328 329
 *
 * One way or another, we guarantee to return some non-empty subset
330
 * of cpu_online_mask.
Linus Torvalds's avatar
Linus Torvalds committed
331
 *
332
 * Call with callback_mutex held.
Linus Torvalds's avatar
Linus Torvalds committed
333
 */
334
static void guarantee_online_cpus(struct cpuset *cs, struct cpumask *pmask)
Linus Torvalds's avatar
Linus Torvalds committed
335
{
336
	while (!cpumask_intersects(cs->effective_cpus, cpu_online_mask))
Tejun Heo's avatar
Tejun Heo committed
337
		cs = parent_cs(cs);
338
	cpumask_and(pmask, cs->effective_cpus, cpu_online_mask);
Linus Torvalds's avatar
Linus Torvalds committed
339 340 341 342
}

/*
 * Return in *pmask the portion of a cpusets's mems_allowed that
343 344
 * are online, with memory.  If none are online with memory, walk
 * up the cpuset hierarchy until we find one that does have some
345
 * online mems.  The top cpuset always has some mems online.
Linus Torvalds's avatar
Linus Torvalds committed
346 347
 *
 * One way or another, we guarantee to return some non-empty subset
348
 * of node_states[N_MEMORY].
Linus Torvalds's avatar
Linus Torvalds committed
349
 *
350
 * Call with callback_mutex held.
Linus Torvalds's avatar
Linus Torvalds committed
351
 */
352
static void guarantee_online_mems(struct cpuset *cs, nodemask_t *pmask)
Linus Torvalds's avatar
Linus Torvalds committed
353
{
354
	while (!nodes_intersects(cs->effective_mems, node_states[N_MEMORY]))
Tejun Heo's avatar
Tejun Heo committed
355
		cs = parent_cs(cs);
356
	nodes_and(*pmask, cs->effective_mems, node_states[N_MEMORY]);
Linus Torvalds's avatar
Linus Torvalds committed
357 358
}

359 360 361
/*
 * update task's spread flag if cpuset's page/slab spread flag is set
 *
362
 * Called with callback_mutex/cpuset_mutex held
363 364 365 366 367 368 369 370 371 372 373 374 375 376
 */
static void cpuset_update_task_spread_flag(struct cpuset *cs,
					struct task_struct *tsk)
{
	if (is_spread_page(cs))
		tsk->flags |= PF_SPREAD_PAGE;
	else
		tsk->flags &= ~PF_SPREAD_PAGE;
	if (is_spread_slab(cs))
		tsk->flags |= PF_SPREAD_SLAB;
	else
		tsk->flags &= ~PF_SPREAD_SLAB;
}

Linus Torvalds's avatar
Linus Torvalds committed
377 378 379 380 381
/*
 * 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
382
 * are only set if the other's are set.  Call holding cpuset_mutex.
Linus Torvalds's avatar
Linus Torvalds committed
383 384 385 386
 */

static int is_cpuset_subset(const struct cpuset *p, const struct cpuset *q)
{
387
	return	cpumask_subset(p->cpus_allowed, q->cpus_allowed) &&
Linus Torvalds's avatar
Linus Torvalds committed
388 389 390 391 392
		nodes_subset(p->mems_allowed, q->mems_allowed) &&
		is_cpu_exclusive(p) <= is_cpu_exclusive(q) &&
		is_mem_exclusive(p) <= is_mem_exclusive(q);
}

393 394 395 396
/**
 * alloc_trial_cpuset - allocate a trial cpuset
 * @cs: the cpuset that the trial cpuset duplicates
 */
397
static struct cpuset *alloc_trial_cpuset(struct cpuset *cs)
398
{
399 400 401 402 403 404
	struct cpuset *trial;

	trial = kmemdup(cs, sizeof(*cs), GFP_KERNEL);
	if (!trial)
		return NULL;

405 406 407 408
	if (!alloc_cpumask_var(&trial->cpus_allowed, GFP_KERNEL))
		goto free_cs;
	if (!alloc_cpumask_var(&trial->effective_cpus, GFP_KERNEL))
		goto free_cpus;
409

410 411
	cpumask_copy(trial->cpus_allowed, cs->cpus_allowed);
	cpumask_copy(trial->effective_cpus, cs->effective_cpus);
412
	return trial;
413 414 415 416 417 418

free_cpus:
	free_cpumask_var(trial->cpus_allowed);
free_cs:
	kfree(trial);
	return NULL;
419 420 421 422 423 424 425 426
}

/**
 * free_trial_cpuset - free the trial cpuset
 * @trial: the trial cpuset to be freed
 */
static void free_trial_cpuset(struct cpuset *trial)
{
427
	free_cpumask_var(trial->effective_cpus);
428
	free_cpumask_var(trial->cpus_allowed);
429 430 431
	kfree(trial);
}

Linus Torvalds's avatar
Linus Torvalds committed
432 433 434 435 436 437 438
/*
 * 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
439
 * cpuset_mutex held.
Linus Torvalds's avatar
Linus Torvalds committed
440 441 442 443 444 445 446 447 448 449 450 451
 *
 * '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.
 */

452
static int validate_change(struct cpuset *cur, struct cpuset *trial)
Linus Torvalds's avatar
Linus Torvalds committed
453
{
454
	struct cgroup_subsys_state *css;
Linus Torvalds's avatar
Linus Torvalds committed
455
	struct cpuset *c, *par;
456 457 458
	int ret;

	rcu_read_lock();
Linus Torvalds's avatar
Linus Torvalds committed
459 460

	/* Each of our child cpusets must be a subset of us */
461
	ret = -EBUSY;
462
	cpuset_for_each_child(c, css, cur)
463 464
		if (!is_cpuset_subset(c, trial))
			goto out;
Linus Torvalds's avatar
Linus Torvalds committed
465 466

	/* Remaining checks don't apply to root cpuset */
467
	ret = 0;
468
	if (cur == &top_cpuset)
469
		goto out;
Linus Torvalds's avatar
Linus Torvalds committed
470

Tejun Heo's avatar
Tejun Heo committed
471
	par = parent_cs(cur);
472

473
	/* On legacy hiearchy, we must be a subset of our parent cpuset. */
474
	ret = -EACCES;
475
	if (!cgroup_on_dfl(cur->css.cgroup) && !is_cpuset_subset(trial, par))
476
		goto out;
Linus Torvalds's avatar
Linus Torvalds committed
477

478 479 480 481
	/*
	 * If either I or some sibling (!= me) is exclusive, we can't
	 * overlap
	 */
482
	ret = -EINVAL;
483
	cpuset_for_each_child(c, css, par) {
Linus Torvalds's avatar
Linus Torvalds committed
484 485
		if ((is_cpu_exclusive(trial) || is_cpu_exclusive(c)) &&
		    c != cur &&
486
		    cpumask_intersects(trial->cpus_allowed, c->cpus_allowed))
487
			goto out;
Linus Torvalds's avatar
Linus Torvalds committed
488 489 490
		if ((is_mem_exclusive(trial) || is_mem_exclusive(c)) &&
		    c != cur &&
		    nodes_intersects(trial->mems_allowed, c->mems_allowed))
491
			goto out;
Linus Torvalds's avatar
Linus Torvalds committed
492 493
	}

494 495
	/*
	 * Cpusets with tasks - existing or newly being attached - can't
496
	 * be changed to have empty cpus_allowed or mems_allowed.
497
	 */
498
	ret = -ENOSPC;
499
	if ((cgroup_has_tasks(cur->css.cgroup) || cur->attach_in_progress)) {
500 501 502 503 504 505 506
		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;
	}
507

508 509 510 511
	ret = 0;
out:
	rcu_read_unlock();
	return ret;
Linus Torvalds's avatar
Linus Torvalds committed
512 513
}

514
#ifdef CONFIG_SMP
Paul Jackson's avatar
Paul Jackson committed
515
/*
516
 * Helper routine for generate_sched_domains().
517
 * Do cpusets a, b have overlapping effective cpus_allowed masks?
Paul Jackson's avatar
Paul Jackson committed
518 519 520
 */
static int cpusets_overlap(struct cpuset *a, struct cpuset *b)
{
521
	return cpumask_intersects(a->effective_cpus, b->effective_cpus);
Paul Jackson's avatar
Paul Jackson committed
522 523
}

524 525 526 527 528 529 530 531
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;
}

532 533
static void update_domain_attr_tree(struct sched_domain_attr *dattr,
				    struct cpuset *root_cs)
534
{
535
	struct cpuset *cp;
536
	struct cgroup_subsys_state *pos_css;
537

538
	rcu_read_lock();
539
	cpuset_for_each_descendant_pre(cp, pos_css, root_cs) {
540 541 542
		if (cp == root_cs)
			continue;

543 544
		/* skip the whole subtree if @cp doesn't have any CPU */
		if (cpumask_empty(cp->cpus_allowed)) {
545
			pos_css = css_rightmost_descendant(pos_css);
546
			continue;
547
		}
548 549 550 551

		if (is_sched_load_balance(cp))
			update_domain_attr(dattr, cp);
	}
552
	rcu_read_unlock();
553 554
}

Paul Jackson's avatar
Paul Jackson committed
555
/*
556 557 558 559 560
 * 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.
561
 * The output of this function needs to be passed to kernel/sched/core.c
562 563 564
 * partition_sched_domains() routine, which will rebuild the scheduler's
 * load balancing domains (sched domains) as specified by that partial
 * partition.
Paul Jackson's avatar
Paul Jackson committed
565
 *
566
 * See "What is sched_load_balance" in Documentation/cgroups/cpusets.txt
Paul Jackson's avatar
Paul Jackson committed
567 568 569 570 571 572 573
 * 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.
 *
574
 * Must be called with cpuset_mutex held.
Paul Jackson's avatar
Paul Jackson committed
575 576
 *
 * The three key local variables below are:
577
 *    q  - a linked-list queue of cpuset pointers, used to implement a
Paul Jackson's avatar
Paul Jackson committed
578 579 580 581 582 583 584 585 586 587 588 589
 *	   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
590
 *	   the kernel/sched/core.c routine partition_sched_domains() in a
Paul Jackson's avatar
Paul Jackson committed
591 592 593 594 595 596 597 598 599 600 601 602 603 604 605 606 607 608
 *	   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().
 */
609
static int generate_sched_domains(cpumask_var_t **domains,
610
			struct sched_domain_attr **attributes)
Paul Jackson's avatar
Paul Jackson committed
611 612 613 614 615
{
	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 */
616
	cpumask_var_t *doms;	/* resulting partition; i.e. sched domains */
617
	struct sched_domain_attr *dattr;  /* attributes for custom domains */
618
	int ndoms = 0;		/* number of sched domains in result */
619
	int nslot;		/* next empty doms[] struct cpumask slot */
620
	struct cgroup_subsys_state *pos_css;
Paul Jackson's avatar
Paul Jackson committed
621 622

	doms = NULL;
623
	dattr = NULL;
624
	csa = NULL;
Paul Jackson's avatar
Paul Jackson committed
625 626 627

	/* Special case for the 99% of systems with one, full, sched domain */
	if (is_sched_load_balance(&top_cpuset)) {
628 629
		ndoms = 1;
		doms = alloc_sched_domains(ndoms);
Paul Jackson's avatar
Paul Jackson committed
630
		if (!doms)
631 632
			goto done;

633 634 635
		dattr = kmalloc(sizeof(struct sched_domain_attr), GFP_KERNEL);
		if (dattr) {
			*dattr = SD_ATTR_INIT;
636
			update_domain_attr_tree(dattr, &top_cpuset);
637
		}
638
		cpumask_copy(doms[0], top_cpuset.effective_cpus);
639 640

		goto done;
Paul Jackson's avatar
Paul Jackson committed
641 642
	}

643
	csa = kmalloc(nr_cpusets() * sizeof(cp), GFP_KERNEL);
Paul Jackson's avatar
Paul Jackson committed
644 645 646 647
	if (!csa)
		goto done;
	csn = 0;

648
	rcu_read_lock();
649
	cpuset_for_each_descendant_pre(cp, pos_css, &top_cpuset) {
650 651
		if (cp == &top_cpuset)
			continue;
652
		/*
653 654 655 656 657 658
		 * 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.
659
		 */
660 661
		if (!cpumask_empty(cp->cpus_allowed) &&
		    !is_sched_load_balance(cp))
662
			continue;
663

664 665 666 667
		if (is_sched_load_balance(cp))
			csa[csn++] = cp;

		/* skip @cp's subtree */
668
		pos_css = css_rightmost_descendant(pos_css);
669 670
	}
	rcu_read_unlock();
Paul Jackson's avatar
Paul Jackson committed
671 672 673 674 675 676 677 678 679 680 681 682 683 684 685 686 687 688 689 690 691 692 693 694 695 696 697 698

	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;
			}
		}
	}

699 700 701 702
	/*
	 * Now we know how many domains to create.
	 * Convert <csn, csa> to <ndoms, doms> and populate cpu masks.
	 */
703
	doms = alloc_sched_domains(ndoms);
704
	if (!doms)
705 706 707 708 709 710
		goto done;

	/*
	 * The rest of the code, including the scheduler, can deal with
	 * dattr==NULL case. No need to abort if alloc fails.
	 */
711
	dattr = kmalloc(ndoms * sizeof(struct sched_domain_attr), GFP_KERNEL);
Paul Jackson's avatar
Paul Jackson committed
712 713 714

	for (nslot = 0, i = 0; i < csn; i++) {
		struct cpuset *a = csa[i];
715
		struct cpumask *dp;
Paul Jackson's avatar
Paul Jackson committed
716 717
		int apn = a->pn;

718 719 720 721 722
		if (apn < 0) {
			/* Skip completed partitions */
			continue;
		}

723
		dp = doms[nslot];
724 725 726 727

		if (nslot == ndoms) {
			static int warnings = 10;
			if (warnings) {
728 729
				pr_warn("rebuild_sched_domains confused: nslot %d, ndoms %d, csn %d, i %d, apn %d\n",
					nslot, ndoms, csn, i, apn);
730
				warnings--;
Paul Jackson's avatar
Paul Jackson committed
731
			}
732 733
			continue;
		}
Paul Jackson's avatar
Paul Jackson committed
734

735
		cpumask_clear(dp);
736 737 738 739 740 741
		if (dattr)
			*(dattr + nslot) = SD_ATTR_INIT;
		for (j = i; j < csn; j++) {
			struct cpuset *b = csa[j];

			if (apn == b->pn) {
742
				cpumask_or(dp, dp, b->effective_cpus);
743 744 745 746 747
				if (dattr)
					update_domain_attr_tree(dattr + nslot, b);

				/* Done with this partition */
				b->pn = -1;
Paul Jackson's avatar
Paul Jackson committed
748 749
			}
		}
750
		nslot++;
Paul Jackson's avatar
Paul Jackson committed
751 752 753
	}
	BUG_ON(nslot != ndoms);

754 755 756
done:
	kfree(csa);

757 758 759 760 761 762 763
	/*
	 * Fallback to the default domain if kmalloc() failed.
	 * See comments in partition_sched_domains().
	 */
	if (doms == NULL)
		ndoms = 1;

764 765 766 767 768 769 770 771
	*domains    = doms;
	*attributes = dattr;
	return ndoms;
}

/*
 * Rebuild scheduler domains.
 *
772 773 774 775 776
 * 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.
777
 *
778
 * Call with cpuset_mutex held.  Takes get_online_cpus().
779
 */
780
static void rebuild_sched_domains_locked(void)
781 782
{
	struct sched_domain_attr *attr;
783
	cpumask_var_t *doms;
784 785
	int ndoms;

786
	lockdep_assert_held(&cpuset_mutex);
787
	get_online_cpus();
788

789 790 791 792 793
	/*
	 * 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.
	 */
794
	if (!cpumask_equal(top_cpuset.effective_cpus, cpu_active_mask))
795 796
		goto out;

797 798 799 800 801
	/* Generate domain masks and attrs */
	ndoms = generate_sched_domains(&doms, &attr);

	/* Have scheduler rebuild the domains */
	partition_sched_domains(ndoms, doms, attr);
802
out:
803
	put_online_cpus();
804
}
805
#else /* !CONFIG_SMP */
806
static void rebuild_sched_domains_locked(void)
807 808 809
{
}
#endif /* CONFIG_SMP */
Paul Jackson's avatar
Paul Jackson committed
810

811 812
void rebuild_sched_domains(void)
{
813
	mutex_lock(&cpuset_mutex);
814
	rebuild_sched_domains_locked();
815
	mutex_unlock(&cpuset_mutex);
Paul Jackson's avatar
Paul Jackson committed
816 817
}

818 819 820 821
/**
 * 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
 *
822 823 824
 * 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.
825
 */
826
static void update_tasks_cpumask(struct cpuset *cs)
827
{
828 829 830 831 832
	struct css_task_iter it;
	struct task_struct *task;

	css_task_iter_start(&cs->css, &it);
	while ((task = css_task_iter_next(&it)))
833
		set_cpus_allowed_ptr(task, cs->effective_cpus);
834
	css_task_iter_end(&it);
835 836
}

837
/*
838 839 840 841 842 843
 * 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.
844
 *
845
 * On legacy hierachy, effective_cpus will be the same with cpu_allowed.
846 847 848
 *
 * Called with cpuset_mutex held
 */
849
static void update_cpumasks_hier(struct cpuset *cs, struct cpumask *new_cpus)
850 851
{
	struct cpuset *cp;
852
	struct cgroup_subsys_state *pos_css;
853
	bool need_rebuild_sched_domains = false;
854 855

	rcu_read_lock();
856 857 858 859 860
	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);

861 862 863 864 865 866 867
		/*
		 * If it becomes empty, inherit the effective mask of the
		 * parent, which is guaranteed to have some CPUs.
		 */
		if (cpumask_empty(new_cpus))
			cpumask_copy(new_cpus, parent->effective_cpus);

868 869 870 871
		/* 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;
872
		}
873

874
		if (!css_tryget_online(&cp->css))
875 876 877
			continue;
		rcu_read_unlock();

878 879 880 881 882 883 884
		mutex_lock(&callback_mutex);
		cpumask_copy(cp->effective_cpus, new_cpus);
		mutex_unlock(&callback_mutex);

		WARN_ON(!cgroup_on_dfl(cp->css.cgroup) &&
			!cpumask_equal(cp->cpus_allowed, cp->effective_cpus));

885
		update_tasks_cpumask(cp);
886

887 888 889 890 891 892 893 894
		/*
		 * 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;

895 896 897 898
		rcu_read_lock();
		css_put(&cp->css);
	}
	rcu_read_unlock();
899 900 901

	if (need_rebuild_sched_domains)
		rebuild_sched_domains_locked();
902 903
}

904 905 906
/**
 * update_cpumask - update the cpus_allowed mask of a cpuset and all tasks in it
 * @cs: the cpuset to consider
907
 * @trialcs: trial cpuset
908 909
 * @buf: buffer of cpu numbers written to this cpuset
 */
910 911
static int update_cpumask(struct cpuset *cs, struct cpuset *trialcs,
			  const char *buf)
Linus Torvalds's avatar
Linus Torvalds committed
912
{
913
	int retval;
Linus Torvalds's avatar
Linus Torvalds committed
914

915
	/* top_cpuset.cpus_allowed tracks cpu_online_mask; it's read-only */
916 917 918
	if (cs == &top_cpuset)
		return -EACCES;

919
	/*
920
	 * An empty cpus_allowed is ok only if the cpuset has no tasks.
921 922 923
	 * Since cpulist_parse() fails on an empty mask, we special case
	 * that parsing.  The validate_change() call ensures that cpusets
	 * with tasks have cpus.
924
	 */
925
	if (!*buf) {
926
		cpumask_clear(trialcs->cpus_allowed);
927
	} else {
928
		retval = cpulist_parse(buf, trialcs->cpus_allowed);
929 930
		if (retval < 0)
			return retval;
931

932
		if (!cpumask_subset(trialcs->cpus_allowed, cpu_active_mask))
933
			return -EINVAL;
934
	}
Paul Jackson's avatar
Paul Jackson committed
935

Paul Menage's avatar
Paul Menage committed
936
	/* Nothing to do if the cpus didn't change */
937
	if (cpumask_equal(cs->cpus_allowed, trialcs->cpus_allowed))
Paul Menage's avatar
Paul Menage committed
938
		return 0;
939

940 941 942 943
	retval = validate_change(cs, trialcs);
	if (retval < 0)
		return retval;

944
	mutex_lock(&callback_mutex);
945
	cpumask_copy(cs->cpus_allowed, trialcs->cpus_allowed);
946
	mutex_unlock(&callback_mutex);
Paul Jackson's avatar
Paul Jackson committed
947

948 949
	/* use trialcs->cpus_allowed as a temp variable */
	update_cpumasks_hier(cs, trialcs->cpus_allowed);
950
	return 0;
Linus Torvalds's avatar
Linus Torvalds committed
951 952
}

953 954 955 956 957 958 959 960 961 962 963 964 965 966 967 968 969 970 971 972 973 974 975
/*
 * cpuset_migrate_mm
 *
 *    Migrate memory region from one set of nodes to another.
 *
 *    Temporarilly set tasks mems_allowed to target nodes of migration,
 *    so that the migration code can allocate pages on these nodes.
 *
 *    While the mm_struct we are migrating is typically from some
 *    other task, the task_struct mems_allowed that we are hacking
 *    is for our current task, which must allocate new pages for that
 *    migrating memory region.
 */

static void cpuset_migrate_mm(struct mm_struct *mm, const nodemask_t *from,
							const nodemask_t *to)
{
	struct task_struct *tsk = current;

	tsk->mems_allowed = *to;

	do_migrate_pages(mm, from, to, MPOL_MF_MOVE_ALL);

976
	rcu_read_lock();
977
	guarantee_online_mems(task_cs(tsk), &tsk->mems_allowed);
978
	rcu_read_unlock();
979 980
}

981
/*
982 983 984 985 986 987 988 989 990 991 992
 * 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)
{
993
	bool need_loop;
994

995 996 997 998 999 1000 1001 1002 1003 1004
	/*
	 * 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;
	if (current->flags & PF_EXITING) /* Let dying task have memory */
		return;

	task_lock(tsk);
1005 1006
	/*
	 * Determine if a loop is necessary if another thread is doing
1007
	 * read_mems_allowed_begin().  If at least one node remains unchanged and
1008 1009 1010 1011 1012
	 * 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);
1013

1014 1015
	if (need_loop) {
		local_irq_disable();
1016
		write_seqcount_begin(&tsk->mems_allowed_seq);
1017
	}
1018

1019 1020
	nodes_or(tsk->mems_allowed, tsk->mems_allowed, *newmems);
	mpol_rebind_task(tsk, newmems, MPOL_REBIND_STEP1);
1021 1022

	mpol_rebind_task(tsk, newmems, MPOL_REBIND_STEP2);
1023
	tsk->mems_allowed = *newmems;
1024

1025
	if (need_loop) {
1026
		write_seqcount_end(&tsk->mems_allowed_seq);
1027 1028
		local_irq_enable();
	}
1029

1030
	task_unlock(tsk);
1031 1032
}

1033 1034
static void *cpuset_being_rebound;

1035 1036 1037 1038
/**
 * 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
 *
1039 1040 1041
 * 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.