cpuset.c 77.3 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 65 66 67 68
/*
 * Tracks how many cpusets are currently defined in system.
 * When there is only one cpuset (the root cpuset) we can
 * short circuit some hooks.
 */
69
int number_of_cpusets __read_mostly;
70

71
/* Forward declare cgroup structures */
72 73
struct cgroup_subsys cpuset_subsys;

74 75 76 77 78 79 80 81 82
/* 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
83
struct cpuset {
84 85
	struct cgroup_subsys_state css;

Linus Torvalds's avatar
Linus Torvalds committed
86
	unsigned long flags;		/* "unsigned long" so bitops work */
87
	cpumask_var_t cpus_allowed;	/* CPUs allowed to tasks in cpuset */
Linus Torvalds's avatar
Linus Torvalds committed
88 89
	nodemask_t mems_allowed;	/* Memory Nodes allowed to tasks */

90 91 92 93 94 95 96 97 98 99 100 101
	/*
	 * 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;

102
	struct fmeter fmeter;		/* memory_pressure filter */
Paul Jackson's avatar
Paul Jackson committed
103

104 105 106 107 108 109
	/*
	 * 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
110 111
	/* partition number for rebuild_sched_domains() */
	int pn;
112

113 114
	/* for custom sched domain */
	int relax_domain_level;
Linus Torvalds's avatar
Linus Torvalds committed
115 116
};

117 118 119 120 121
static inline struct cpuset *css_cs(struct cgroup_subsys_state *css)
{
	return css ? container_of(css, struct cpuset, css) : NULL;
}

122 123 124
/* Retrieve the cpuset for a task */
static inline struct cpuset *task_cs(struct task_struct *task)
{
125
	return css_cs(task_css(task, cpuset_subsys_id));
126 127
}

128
static inline struct cpuset *parent_cs(struct cpuset *cs)
Tejun Heo's avatar
Tejun Heo committed
129
{
Tejun Heo's avatar
Tejun Heo committed
130
	return css_cs(css_parent(&cs->css));
Tejun Heo's avatar
Tejun Heo committed
131 132
}

133 134 135 136 137 138 139 140 141 142 143 144 145
#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
146 147
/* bits in struct cpuset flags field */
typedef enum {
Tejun Heo's avatar
Tejun Heo committed
148
	CS_ONLINE,
Linus Torvalds's avatar
Linus Torvalds committed
149 150
	CS_CPU_EXCLUSIVE,
	CS_MEM_EXCLUSIVE,
151
	CS_MEM_HARDWALL,
152
	CS_MEMORY_MIGRATE,
Paul Jackson's avatar
Paul Jackson committed
153
	CS_SCHED_LOAD_BALANCE,
154 155
	CS_SPREAD_PAGE,
	CS_SPREAD_SLAB,
Linus Torvalds's avatar
Linus Torvalds committed
156 157 158
} cpuset_flagbits_t;

/* convenient tests for these bits */
Tejun Heo's avatar
Tejun Heo committed
159 160 161 162 163
static inline bool is_cpuset_online(const struct cpuset *cs)
{
	return test_bit(CS_ONLINE, &cs->flags);
}

Linus Torvalds's avatar
Linus Torvalds committed
164 165
static inline int is_cpu_exclusive(const struct cpuset *cs)
{
166
	return test_bit(CS_CPU_EXCLUSIVE, &cs->flags);
Linus Torvalds's avatar
Linus Torvalds committed
167 168 169 170
}

static inline int is_mem_exclusive(const struct cpuset *cs)
{
171
	return test_bit(CS_MEM_EXCLUSIVE, &cs->flags);
Linus Torvalds's avatar
Linus Torvalds committed
172 173
}

174 175 176 177 178
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
179 180 181 182 183
static inline int is_sched_load_balance(const struct cpuset *cs)
{
	return test_bit(CS_SCHED_LOAD_BALANCE, &cs->flags);
}

184 185
static inline int is_memory_migrate(const struct cpuset *cs)
{
186
	return test_bit(CS_MEMORY_MIGRATE, &cs->flags);
187 188
}

189 190 191 192 193 194 195 196 197 198
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
199
static struct cpuset top_cpuset = {
Tejun Heo's avatar
Tejun Heo committed
200 201
	.flags = ((1 << CS_ONLINE) | (1 << CS_CPU_EXCLUSIVE) |
		  (1 << CS_MEM_EXCLUSIVE)),
Linus Torvalds's avatar
Linus Torvalds committed
202 203
};

204 205 206
/**
 * cpuset_for_each_child - traverse online children of a cpuset
 * @child_cs: loop cursor pointing to the current child
207
 * @pos_css: used for iteration
208 209 210 211 212
 * @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.
 */
213 214 215
#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)))))
216

217 218 219
/**
 * cpuset_for_each_descendant_pre - pre-order walk of a cpuset's descendants
 * @des_cs: loop cursor pointing to the current descendant
220
 * @pos_css: used for iteration
221 222 223
 * @root_cs: target cpuset to walk ancestor of
 *
 * Walk @des_cs through the online descendants of @root_cs.  Must be used
224 225
 * with RCU read locked.  The caller may modify @pos_css by calling
 * css_rightmost_descendant() to skip subtree.
226
 */
227 228 229
#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)))))
230

Linus Torvalds's avatar
Linus Torvalds committed
231
/*
232 233 234 235 236 237 238 239 240 241 242 243 244 245
 * 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.
246 247
 *
 * Calls to the kernel memory allocator can not be made while holding
248
 * callback_mutex, as that would risk double tripping on callback_mutex
249 250 251
 * from one of the callbacks into the cpuset code from within
 * __alloc_pages().
 *
252
 * If a task is only holding callback_mutex, then it has read-only
253 254
 * access to cpusets.
 *
255 256 257
 * 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.
258
 *
259
 * The cpuset_common_file_read() handlers only hold callback_mutex across
260 261 262
 * small pieces of code, such as when reading out possibly multi-word
 * cpumasks and nodemasks.
 *
263 264
 * 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
265 266
 */

267
static DEFINE_MUTEX(cpuset_mutex);
268
static DEFINE_MUTEX(callback_mutex);
269

270 271 272 273 274 275
/*
 * CPU / memory hotplug is handled asynchronously.
 */
static void cpuset_hotplug_workfn(struct work_struct *work);
static DECLARE_WORK(cpuset_hotplug_work, cpuset_hotplug_workfn);

276 277
static DECLARE_WAIT_QUEUE_HEAD(cpuset_attach_wq);

278 279
/*
 * This is ugly, but preserves the userspace API for existing cpuset
280
 * users. If someone tries to mount the "cpuset" filesystem, we
281 282
 * silently switch it to mount "cgroup" instead
 */
Al Viro's avatar
Al Viro committed
283 284
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
285
{
286
	struct file_system_type *cgroup_fs = get_fs_type("cgroup");
Al Viro's avatar
Al Viro committed
287
	struct dentry *ret = ERR_PTR(-ENODEV);
288 289 290 291
	if (cgroup_fs) {
		char mountopts[] =
			"cpuset,noprefix,"
			"release_agent=/sbin/cpuset_release_agent";
Al Viro's avatar
Al Viro committed
292 293
		ret = cgroup_fs->mount(cgroup_fs, flags,
					   unused_dev_name, mountopts);
294 295 296
		put_filesystem(cgroup_fs);
	}
	return ret;
Linus Torvalds's avatar
Linus Torvalds committed
297 298 299 300
}

static struct file_system_type cpuset_fs_type = {
	.name = "cpuset",
Al Viro's avatar
Al Viro committed
301
	.mount = cpuset_mount,
Linus Torvalds's avatar
Linus Torvalds committed
302 303 304
};

/*
305
 * Return in pmask the portion of a cpusets's cpus_allowed that
Linus Torvalds's avatar
Linus Torvalds committed
306
 * are online.  If none are online, walk up the cpuset hierarchy
307 308
 * 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
309 310
 *
 * One way or another, we guarantee to return some non-empty subset
311
 * of cpu_online_mask.
Linus Torvalds's avatar
Linus Torvalds committed
312
 *
313
 * Call with callback_mutex held.
Linus Torvalds's avatar
Linus Torvalds committed
314
 */
315
static void guarantee_online_cpus(struct cpuset *cs, struct cpumask *pmask)
Linus Torvalds's avatar
Linus Torvalds committed
316
{
317
	while (!cpumask_intersects(cs->cpus_allowed, cpu_online_mask))
Tejun Heo's avatar
Tejun Heo committed
318
		cs = parent_cs(cs);
319
	cpumask_and(pmask, cs->cpus_allowed, cpu_online_mask);
Linus Torvalds's avatar
Linus Torvalds committed
320 321 322 323
}

/*
 * Return in *pmask the portion of a cpusets's mems_allowed that
324 325
 * are online, with memory.  If none are online with memory, walk
 * up the cpuset hierarchy until we find one that does have some
326
 * online mems.  The top cpuset always has some mems online.
Linus Torvalds's avatar
Linus Torvalds committed
327 328
 *
 * One way or another, we guarantee to return some non-empty subset
329
 * of node_states[N_MEMORY].
Linus Torvalds's avatar
Linus Torvalds committed
330
 *
331
 * Call with callback_mutex held.
Linus Torvalds's avatar
Linus Torvalds committed
332
 */
333
static void guarantee_online_mems(struct cpuset *cs, nodemask_t *pmask)
Linus Torvalds's avatar
Linus Torvalds committed
334
{
335
	while (!nodes_intersects(cs->mems_allowed, node_states[N_MEMORY]))
Tejun Heo's avatar
Tejun Heo committed
336
		cs = parent_cs(cs);
337
	nodes_and(*pmask, cs->mems_allowed, node_states[N_MEMORY]);
Linus Torvalds's avatar
Linus Torvalds committed
338 339
}

340 341 342
/*
 * update task's spread flag if cpuset's page/slab spread flag is set
 *
343
 * Called with callback_mutex/cpuset_mutex held
344 345 346 347 348 349 350 351 352 353 354 355 356 357
 */
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
358 359 360 361 362
/*
 * 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
363
 * are only set if the other's are set.  Call holding cpuset_mutex.
Linus Torvalds's avatar
Linus Torvalds committed
364 365 366 367
 */

static int is_cpuset_subset(const struct cpuset *p, const struct cpuset *q)
{
368
	return	cpumask_subset(p->cpus_allowed, q->cpus_allowed) &&
Linus Torvalds's avatar
Linus Torvalds committed
369 370 371 372 373
		nodes_subset(p->mems_allowed, q->mems_allowed) &&
		is_cpu_exclusive(p) <= is_cpu_exclusive(q) &&
		is_mem_exclusive(p) <= is_mem_exclusive(q);
}

374 375 376 377
/**
 * alloc_trial_cpuset - allocate a trial cpuset
 * @cs: the cpuset that the trial cpuset duplicates
 */
378
static struct cpuset *alloc_trial_cpuset(struct cpuset *cs)
379
{
380 381 382 383 384 385 386 387 388 389 390 391 392
	struct cpuset *trial;

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

	if (!alloc_cpumask_var(&trial->cpus_allowed, GFP_KERNEL)) {
		kfree(trial);
		return NULL;
	}
	cpumask_copy(trial->cpus_allowed, cs->cpus_allowed);

	return trial;
393 394 395 396 397 398 399 400
}

/**
 * free_trial_cpuset - free the trial cpuset
 * @trial: the trial cpuset to be freed
 */
static void free_trial_cpuset(struct cpuset *trial)
{
401
	free_cpumask_var(trial->cpus_allowed);
402 403 404
	kfree(trial);
}

Linus Torvalds's avatar
Linus Torvalds committed
405 406 407 408 409 410 411
/*
 * 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
412
 * cpuset_mutex held.
Linus Torvalds's avatar
Linus Torvalds committed
413 414 415 416 417 418 419 420 421 422 423 424
 *
 * '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.
 */

425
static int validate_change(struct cpuset *cur, struct cpuset *trial)
Linus Torvalds's avatar
Linus Torvalds committed
426
{
427
	struct cgroup_subsys_state *css;
Linus Torvalds's avatar
Linus Torvalds committed
428
	struct cpuset *c, *par;
429 430 431
	int ret;

	rcu_read_lock();
Linus Torvalds's avatar
Linus Torvalds committed
432 433

	/* Each of our child cpusets must be a subset of us */
434
	ret = -EBUSY;
435
	cpuset_for_each_child(c, css, cur)
436 437
		if (!is_cpuset_subset(c, trial))
			goto out;
Linus Torvalds's avatar
Linus Torvalds committed
438 439

	/* Remaining checks don't apply to root cpuset */
440
	ret = 0;
441
	if (cur == &top_cpuset)
442
		goto out;
Linus Torvalds's avatar
Linus Torvalds committed
443

Tejun Heo's avatar
Tejun Heo committed
444
	par = parent_cs(cur);
445

Linus Torvalds's avatar
Linus Torvalds committed
446
	/* We must be a subset of our parent cpuset */
447
	ret = -EACCES;
Linus Torvalds's avatar
Linus Torvalds committed
448
	if (!is_cpuset_subset(trial, par))
449
		goto out;
Linus Torvalds's avatar
Linus Torvalds committed
450

451 452 453 454
	/*
	 * If either I or some sibling (!= me) is exclusive, we can't
	 * overlap
	 */
455
	ret = -EINVAL;
456
	cpuset_for_each_child(c, css, par) {
Linus Torvalds's avatar
Linus Torvalds committed
457 458
		if ((is_cpu_exclusive(trial) || is_cpu_exclusive(c)) &&
		    c != cur &&
459
		    cpumask_intersects(trial->cpus_allowed, c->cpus_allowed))
460
			goto out;
Linus Torvalds's avatar
Linus Torvalds committed
461 462 463
		if ((is_mem_exclusive(trial) || is_mem_exclusive(c)) &&
		    c != cur &&
		    nodes_intersects(trial->mems_allowed, c->mems_allowed))
464
			goto out;
Linus Torvalds's avatar
Linus Torvalds committed
465 466
	}

467 468 469 470
	/*
	 * Cpusets with tasks - existing or newly being attached - can't
	 * have empty cpus_allowed or mems_allowed.
	 */
471
	ret = -ENOSPC;
472
	if ((cgroup_task_count(cur->css.cgroup) || cur->attach_in_progress) &&
473
	    (cpumask_empty(trial->cpus_allowed) &&
474 475
	     nodes_empty(trial->mems_allowed)))
		goto out;
476

477 478 479 480
	ret = 0;
out:
	rcu_read_unlock();
	return ret;
Linus Torvalds's avatar
Linus Torvalds committed
481 482
}

483
#ifdef CONFIG_SMP
Paul Jackson's avatar
Paul Jackson committed
484
/*
485
 * Helper routine for generate_sched_domains().
Paul Jackson's avatar
Paul Jackson committed
486 487 488 489
 * Do cpusets a, b have overlapping cpus_allowed masks?
 */
static int cpusets_overlap(struct cpuset *a, struct cpuset *b)
{
490
	return cpumask_intersects(a->cpus_allowed, b->cpus_allowed);
Paul Jackson's avatar
Paul Jackson committed
491 492
}

493 494 495 496 497 498 499 500
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;
}

501 502
static void update_domain_attr_tree(struct sched_domain_attr *dattr,
				    struct cpuset *root_cs)
503
{
504
	struct cpuset *cp;
505
	struct cgroup_subsys_state *pos_css;
506

507
	rcu_read_lock();
508
	cpuset_for_each_descendant_pre(cp, pos_css, root_cs) {
509 510
		/* skip the whole subtree if @cp doesn't have any CPU */
		if (cpumask_empty(cp->cpus_allowed)) {
511
			pos_css = css_rightmost_descendant(pos_css);
512
			continue;
513
		}
514 515 516 517

		if (is_sched_load_balance(cp))
			update_domain_attr(dattr, cp);
	}
518
	rcu_read_unlock();
519 520
}

Paul Jackson's avatar
Paul Jackson committed
521
/*
522 523 524 525 526
 * 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.
527
 * The output of this function needs to be passed to kernel/sched/core.c
528 529 530
 * 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
531
 *
532
 * See "What is sched_load_balance" in Documentation/cgroups/cpusets.txt
Paul Jackson's avatar
Paul Jackson committed
533 534 535 536 537 538 539
 * 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.
 *
540
 * Must be called with cpuset_mutex held.
Paul Jackson's avatar
Paul Jackson committed
541 542
 *
 * The three key local variables below are:
543
 *    q  - a linked-list queue of cpuset pointers, used to implement a
Paul Jackson's avatar
Paul Jackson committed
544 545 546 547 548 549 550 551 552 553 554 555
 *	   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
556
 *	   the kernel/sched/core.c routine partition_sched_domains() in a
Paul Jackson's avatar
Paul Jackson committed
557 558 559 560 561 562 563 564 565 566 567 568 569 570 571 572 573 574
 *	   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().
 */
575
static int generate_sched_domains(cpumask_var_t **domains,
576
			struct sched_domain_attr **attributes)
Paul Jackson's avatar
Paul Jackson committed
577 578 579 580 581
{
	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 */
582
	cpumask_var_t *doms;	/* resulting partition; i.e. sched domains */
583
	struct sched_domain_attr *dattr;  /* attributes for custom domains */
584
	int ndoms = 0;		/* number of sched domains in result */
585
	int nslot;		/* next empty doms[] struct cpumask slot */
586
	struct cgroup_subsys_state *pos_css;
Paul Jackson's avatar
Paul Jackson committed
587 588

	doms = NULL;
589
	dattr = NULL;
590
	csa = NULL;
Paul Jackson's avatar
Paul Jackson committed
591 592 593

	/* Special case for the 99% of systems with one, full, sched domain */
	if (is_sched_load_balance(&top_cpuset)) {
594 595
		ndoms = 1;
		doms = alloc_sched_domains(ndoms);
Paul Jackson's avatar
Paul Jackson committed
596
		if (!doms)
597 598
			goto done;

599 600 601
		dattr = kmalloc(sizeof(struct sched_domain_attr), GFP_KERNEL);
		if (dattr) {
			*dattr = SD_ATTR_INIT;
602
			update_domain_attr_tree(dattr, &top_cpuset);
603
		}
604
		cpumask_copy(doms[0], top_cpuset.cpus_allowed);
605 606

		goto done;
Paul Jackson's avatar
Paul Jackson committed
607 608 609 610 611 612 613
	}

	csa = kmalloc(number_of_cpusets * sizeof(cp), GFP_KERNEL);
	if (!csa)
		goto done;
	csn = 0;

614
	rcu_read_lock();
615
	cpuset_for_each_descendant_pre(cp, pos_css, &top_cpuset) {
616
		/*
617 618 619 620 621 622
		 * 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.
623
		 */
624 625
		if (!cpumask_empty(cp->cpus_allowed) &&
		    !is_sched_load_balance(cp))
626
			continue;
627

628 629 630 631
		if (is_sched_load_balance(cp))
			csa[csn++] = cp;

		/* skip @cp's subtree */
632
		pos_css = css_rightmost_descendant(pos_css);
633 634
	}
	rcu_read_unlock();
Paul Jackson's avatar
Paul Jackson committed
635 636 637 638 639 640 641 642 643 644 645 646 647 648 649 650 651 652 653 654 655 656 657 658 659 660 661 662

	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;
			}
		}
	}

663 664 665 666
	/*
	 * Now we know how many domains to create.
	 * Convert <csn, csa> to <ndoms, doms> and populate cpu masks.
	 */
667
	doms = alloc_sched_domains(ndoms);
668
	if (!doms)
669 670 671 672 673 674
		goto done;

	/*
	 * The rest of the code, including the scheduler, can deal with
	 * dattr==NULL case. No need to abort if alloc fails.
	 */
675
	dattr = kmalloc(ndoms * sizeof(struct sched_domain_attr), GFP_KERNEL);
Paul Jackson's avatar
Paul Jackson committed
676 677 678

	for (nslot = 0, i = 0; i < csn; i++) {
		struct cpuset *a = csa[i];
679
		struct cpumask *dp;
Paul Jackson's avatar
Paul Jackson committed
680 681
		int apn = a->pn;

682 683 684 685 686
		if (apn < 0) {
			/* Skip completed partitions */
			continue;
		}

687
		dp = doms[nslot];
688 689 690 691 692 693 694 695 696 697

		if (nslot == ndoms) {
			static int warnings = 10;
			if (warnings) {
				printk(KERN_WARNING
				 "rebuild_sched_domains confused:"
				  " nslot %d, ndoms %d, csn %d, i %d,"
				  " apn %d\n",
				  nslot, ndoms, csn, i, apn);
				warnings--;
Paul Jackson's avatar
Paul Jackson committed
698
			}
699 700
			continue;
		}
Paul Jackson's avatar
Paul Jackson committed
701

702
		cpumask_clear(dp);
703 704 705 706 707 708
		if (dattr)
			*(dattr + nslot) = SD_ATTR_INIT;
		for (j = i; j < csn; j++) {
			struct cpuset *b = csa[j];

			if (apn == b->pn) {
709
				cpumask_or(dp, dp, b->cpus_allowed);
710 711 712 713 714
				if (dattr)
					update_domain_attr_tree(dattr + nslot, b);

				/* Done with this partition */
				b->pn = -1;
Paul Jackson's avatar
Paul Jackson committed
715 716
			}
		}
717
		nslot++;
Paul Jackson's avatar
Paul Jackson committed
718 719 720
	}
	BUG_ON(nslot != ndoms);

721 722 723
done:
	kfree(csa);

724 725 726 727 728 729 730
	/*
	 * Fallback to the default domain if kmalloc() failed.
	 * See comments in partition_sched_domains().
	 */
	if (doms == NULL)
		ndoms = 1;

731 732 733 734 735 736 737 738
	*domains    = doms;
	*attributes = dattr;
	return ndoms;
}

/*
 * Rebuild scheduler domains.
 *
739 740 741 742 743
 * 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.
744
 *
745
 * Call with cpuset_mutex held.  Takes get_online_cpus().
746
 */
747
static void rebuild_sched_domains_locked(void)
748 749
{
	struct sched_domain_attr *attr;
750
	cpumask_var_t *doms;
751 752
	int ndoms;

753
	lockdep_assert_held(&cpuset_mutex);
754
	get_online_cpus();
755

756 757 758 759 760 761 762 763
	/*
	 * 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.cpus_allowed, cpu_active_mask))
		goto out;

764 765 766 767 768
	/* Generate domain masks and attrs */
	ndoms = generate_sched_domains(&doms, &attr);

	/* Have scheduler rebuild the domains */
	partition_sched_domains(ndoms, doms, attr);
769
out:
770
	put_online_cpus();
771
}
772
#else /* !CONFIG_SMP */
773
static void rebuild_sched_domains_locked(void)
774 775 776
{
}
#endif /* CONFIG_SMP */
Paul Jackson's avatar
Paul Jackson committed
777

778 779
void rebuild_sched_domains(void)
{
780
	mutex_lock(&cpuset_mutex);
781
	rebuild_sched_domains_locked();
782
	mutex_unlock(&cpuset_mutex);
Paul Jackson's avatar
Paul Jackson committed
783 784
}

785 786 787
/*
 * effective_cpumask_cpuset - return nearest ancestor with non-empty cpus
 * @cs: the cpuset in interest
788
 *
789 790 791 792 793 794 795 796 797 798 799 800 801 802 803 804 805 806 807 808 809 810 811 812 813 814 815
 * A cpuset's effective cpumask is the cpumask of the nearest ancestor
 * with non-empty cpus. We use effective cpumask whenever:
 * - we update tasks' cpus_allowed. (they take on the ancestor's cpumask
 *   if the cpuset they reside in has no cpus)
 * - we want to retrieve task_cs(tsk)'s cpus_allowed.
 *
 * Called with cpuset_mutex held. cpuset_cpus_allowed_fallback() is an
 * exception. See comments there.
 */
static struct cpuset *effective_cpumask_cpuset(struct cpuset *cs)
{
	while (cpumask_empty(cs->cpus_allowed))
		cs = parent_cs(cs);
	return cs;
}

/*
 * effective_nodemask_cpuset - return nearest ancestor with non-empty mems
 * @cs: the cpuset in interest
 *
 * A cpuset's effective nodemask is the nodemask of the nearest ancestor
 * with non-empty memss. We use effective nodemask whenever:
 * - we update tasks' mems_allowed. (they take on the ancestor's nodemask
 *   if the cpuset they reside in has no mems)
 * - we want to retrieve task_cs(tsk)'s mems_allowed.
 *
 * Called with cpuset_mutex held.
816
 */
817
static struct cpuset *effective_nodemask_cpuset(struct cpuset *cs)
818
{
819 820 821
	while (nodes_empty(cs->mems_allowed))
		cs = parent_cs(cs);
	return cs;
822
}
823

824 825 826
/**
 * cpuset_change_cpumask - make a task's cpus_allowed the same as its cpuset's
 * @tsk: task to test
827
 * @data: cpuset to @tsk belongs to
828
 *
829 830
 * Called by css_scan_tasks() for each task in a cgroup whose cpus_allowed
 * mask needs to be changed.
831 832
 *
 * We don't need to re-check for the cgroup/cpuset membership, since we're
833
 * holding cpuset_mutex at this point.
834
 */
835
static void cpuset_change_cpumask(struct task_struct *tsk, void *data)
836
{
837 838
	struct cpuset *cs = data;
	struct cpuset *cpus_cs = effective_cpumask_cpuset(cs);
839 840

	set_cpus_allowed_ptr(tsk, cpus_cs->cpus_allowed);
841 842
}

843 844 845
/**
 * 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
846
 * @heap: if NULL, defer allocating heap memory to css_scan_tasks()
847
 *
848
 * Called with cpuset_mutex held
849
 *
850
 * The css_scan_tasks() function will scan all the tasks in a cgroup,
851 852
 * calling callback functions for each.
 *
853
 * No return value. It's guaranteed that css_scan_tasks() always returns 0
854
 * if @heap != NULL.
855
 */
856
static void update_tasks_cpumask(struct cpuset *cs, struct ptr_heap *heap)
857
{
858
	css_scan_tasks(&cs->css, NULL, cpuset_change_cpumask, cs, heap);
859 860
}

861 862 863 864
/*
 * update_tasks_cpumask_hier - Update the cpumasks of tasks in the hierarchy.
 * @root_cs: the root cpuset of the hierarchy
 * @update_root: update root cpuset or not?
865
 * @heap: the heap used by css_scan_tasks()
866 867 868 869 870 871 872 873 874 875
 *
 * This will update cpumasks of tasks in @root_cs and all other empty cpusets
 * which take on cpumask of @root_cs.
 *
 * Called with cpuset_mutex held
 */
static void update_tasks_cpumask_hier(struct cpuset *root_cs,
				      bool update_root, struct ptr_heap *heap)
{
	struct cpuset *cp;
876
	struct cgroup_subsys_state *pos_css;
877 878 879 880 881

	if (update_root)
		update_tasks_cpumask(root_cs, heap);

	rcu_read_lock();
882
	cpuset_for_each_descendant_pre(cp, pos_css, root_cs) {
883 884
		/* skip the whole subtree if @cp have some CPU */
		if (!cpumask_empty(cp->cpus_allowed)) {
885
			pos_css = css_rightmost_descendant(pos_css);
886 887 888 889 890 891 892 893 894 895 896 897 898 899
			continue;
		}
		if (!css_tryget(&cp->css))
			continue;
		rcu_read_unlock();

		update_tasks_cpumask(cp, heap);

		rcu_read_lock();
		css_put(&cp->css);
	}
	rcu_read_unlock();
}

900 901 902 903 904
/**
 * update_cpumask - update the cpus_allowed mask of a cpuset and all tasks in it
 * @cs: the cpuset to consider
 * @buf: buffer of cpu numbers written to this cpuset
 */
905 906
static int update_cpumask(struct cpuset *cs, struct cpuset *trialcs,
			  const char *buf)
Linus Torvalds's avatar
Linus Torvalds committed
907
{
908
	struct ptr_heap heap;
909 910
	int retval;
	int is_load_balanced;
Linus Torvalds's avatar
Linus Torvalds committed
911

912
	/* top_cpuset.cpus_allowed tracks cpu_online_mask; it's read-only */
913 914 915
	if (cs == &top_cpuset)
		return -EACCES;

916
	/*
917
	 * An empty cpus_allowed is ok only if the cpuset has no tasks.
918 919 920
	 * Since cpulist_parse() fails on an empty mask, we special case
	 * that parsing.  The validate_change() call ensures that cpusets
	 * with tasks have cpus.
921
	 */
922
	if (!*buf) {
923
		cpumask_clear(trialcs->cpus_allowed);
924
	} else {
925
		retval = cpulist_parse(buf, trialcs->cpus_allowed);
926 927
		if (retval < 0)
			return retval;
928

929
		if (!cpumask_subset(trialcs->cpus_allowed, cpu_active_mask))
930
			return -EINVAL;
931
	}
Paul Jackson's avatar
Paul Jackson committed
932

Paul Menage's avatar
Paul Menage committed
933
	/* Nothing to do if the cpus didn't change */
934
	if (cpumask_equal(cs->cpus_allowed, trialcs->cpus_allowed))
Paul Menage's avatar
Paul Menage committed
935
		return 0;
936

937 938 939 940
	retval = validate_change(cs, trialcs);
	if (retval < 0)
		return retval;

941 942 943 944
	retval = heap_init(&heap, PAGE_SIZE, GFP_KERNEL, NULL);
	if (retval)
		return retval;

945
	is_load_balanced = is_sched_load_balance(trialcs);
Paul Jackson's avatar
Paul Jackson committed
946

947
	mutex_lock(&callback_mutex);
948
	cpumask_copy(cs->cpus_allowed, trialcs->cpus_allowed);
949
	mutex_unlock(&callback_mutex);
Paul Jackson's avatar
Paul Jackson committed
950

951
	update_tasks_cpumask_hier(cs, true, &heap);
952 953

	heap_free(&heap);
954

Paul Menage's avatar
Paul Menage committed
955
	if (is_load_balanced)
956
		rebuild_sched_domains_locked();
957
	return 0;
Linus Torvalds's avatar
Linus Torvalds committed
958 959
}

960 961 962 963 964 965 966 967
/*
 * 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.
 *
968
 *    Call holding cpuset_mutex, so current's cpuset won't change
969
 *    during this call, as manage_mutex holds off any cpuset_attach()
970 971
 *    calls.  Therefore we don't need to take task_lock around the
 *    call to guarantee_online_mems(), as we know no one is changing
972
 *    our task's cpuset.
973 974 975 976 977 978 979 980 981 982 983
 *
 *    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;
984
	struct cpuset *mems_cs;
985 986 987 988 989

	tsk->mems_allowed = *to;

	do_migrate_pages(mm, from, to, MPOL_MF_MOVE_ALL);

990 991
	mems_cs = effective_nodemask_cpuset(task_cs(tsk));
	guarantee_online_mems(mems_cs, &tsk->mems_allowed);
992 993
}

994
/*
995 996 997 998 999 1000 1001 1002 1003 1004 1005
 * 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)
{
1006
	bool need_loop;
1007

1008 1009 1010 1011 1012 1013 1014 1015 1016 1017
	/*
	 * 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);
1018 1019 1020 1021 1022 1023 1024 1025
	/*
	 * Determine if a loop is necessary if another thread is doing
	 * get_mems_allowed().  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);
1026

1027 1028
	if (need_loop)
		write_seqcount_begin(&tsk->mems_allowed_seq);
1029

1030 1031
	nodes_or(tsk->mems_allowed, tsk->mems_allowed, *newmems);
	mpol_rebind_task(tsk, newmems, MPOL_REBIND_STEP1);
1032 1033

	mpol_rebind_task(tsk, newmems, MPOL_REBIND_STEP2);
1034
	tsk->mems_allowed = *newmems;
1035 1036 1037 1038

	if (need_loop)
		write_seqcount_end(&tsk->mems_allowed_seq);

1039
	task_unlock(tsk);
1040 1041
}

1042 1043 1044 1045 1046
struct cpuset_change_nodemask_arg {
	struct cpuset		*cs;
	nodemask_t		*newmems;
};

1047 1048 1049
/*
 * Update task's mems_allowed and rebind its mempolicy and vmas' mempolicy
 * of it to cpuset's new mems_allowed, and migrate pages to new nodes if
1050
 * memory_migrate flag is set. Called with cpuset_mutex held.
1051
 */
1052
static void cpuset_change_nodemask(struct task_struct *p, void *data)
1053
{