lib/cpumask.c

// SPDX-License-Identifier: GPL-2.0
#include <linux/slab.h>
#include <linux/kernel.h>
#include <linux/bitops.h>
#include <linux/string.h>
#include <linux/ctype.h>
#include <linux/cpumask.h>
#include <linux/export.h>
#include <linux/memblock.h>
#include <linux/numa.h>
#include <linux/sched/isolation.h>

/**
 * cpumask_next - get the next cpu in a cpumask
 * @n: the cpu prior to the place to search (ie. return will be > @n)
 * @srcp: the cpumask pointer
 *
 * Returns >= nr_cpu_ids if no further cpus set.
 */
unsigned int cpumask_next(int n, const struct cpumask *srcp)
{
	/* -1 is a legal arg here. */
	if (n != -1)
		cpumask_check(n);
	return find_next_bit(cpumask_bits(srcp), nr_cpumask_bits, n + 1);
}
EXPORT_SYMBOL(cpumask_next);

/**
 * cpumask_next_and - get the next cpu in *src1p & *src2p
 * @n: the cpu prior to the place to search (ie. return will be > @n)
 * @src1p: the first cpumask pointer
 * @src2p: the second cpumask pointer
 *
 * Returns >= nr_cpu_ids if no further cpus set in both.
 */
int cpumask_next_and(int n, const struct cpumask *src1p,
		     const struct cpumask *src2p)
{
	/* -1 is a legal arg here. */
	if (n != -1)
		cpumask_check(n);
	return find_next_and_bit(cpumask_bits(src1p), cpumask_bits(src2p),
		nr_cpumask_bits, n + 1);
}
EXPORT_SYMBOL(cpumask_next_and);

/**
 * cpumask_any_but - return a "random" in a cpumask, but not this one.
 * @mask: the cpumask to search
 * @cpu: the cpu to ignore.
 *
 * Often used to find any cpu but smp_processor_id() in a mask.
 * Returns >= nr_cpu_ids if no cpus set.
 */
int cpumask_any_but(const struct cpumask *mask, unsigned int cpu)
{
	unsigned int i;

	cpumask_check(cpu);
	for_each_cpu(i, mask)
		if (i != cpu)
			break;
	return i;
}
EXPORT_SYMBOL(cpumask_any_but);

/**
 * cpumask_next_wrap - helper to implement for_each_cpu_wrap
 * @n: the cpu prior to the place to search
 * @mask: the cpumask pointer
 * @start: the start point of the iteration
 * @wrap: assume @n crossing @start terminates the iteration
 *
 * Returns >= nr_cpu_ids on completion
 *
 * Note: the @wrap argument is required for the start condition when
 * we cannot assume @start is set in @mask.
 */
int cpumask_next_wrap(int n, const struct cpumask *mask, int start, bool wrap)
{
	int next;

again:
	next = cpumask_next(n, mask);

	if (wrap && n < start && next >= start) {
		return nr_cpumask_bits;

	} else if (next >= nr_cpumask_bits) {
		wrap = true;
		n = -1;
		goto again;
	}

	return next;
}
EXPORT_SYMBOL(cpumask_next_wrap);

/*
 * Basically strstr() but given "foo", ignore "foobar", "myfoo", "foofoo"
 * and "foo2bar" -- i.e. any case where the token is a word fragment.
 */
static char *cpumask_find_token(const char *str, const char *token)
{
	char *here = strstr(str, token);
	size_t tlen = strlen(token);

	if (!here)
		return NULL;

	while (here) {
		size_t offset = here - str;
		char prev, next = str[offset + tlen];

		if (offset)
			prev = str[offset - 1];
		else
			prev = '\0';

		if (!(isalnum(prev) || isalnum(next)))
			break;

		here = strstr(here + tlen, token);
	}

	return here;
}

/*
 * replace old token with new token: Given a convenience or placeholder
 * token "last" and an associated value not known until boot, of say 1234,
 * replace instances of "last" with "1234".
 *
 * For example src = "1,3,last,7-last,9,lastly,last-2047\0"  results in a
 *            dest = "1,3,1234,7-1234,9,lastly,1234-2047\0"
 *
 * The destination string may be shorter than, equal to, or longer than
 * the source string -- based on whether the new token strlen is shorter
 * than, equal to, or longer than the old token strlen.
 * The caller must allocate dest space accordingly with that in mind.
 */

static void cpulist_replace_token(char *dest, const char *src,
			   const char *old_token, const char *new_token)
{
	const char *src_start = src;
	char *dest_start = dest, *here;
	const size_t olen = strlen(old_token);
	const size_t nlen = strlen(new_token);

	here = cpumask_find_token(src_start, old_token);
	if (!here) {
		strcpy(dest, src);
		return;
	}

	while (here) {
		size_t offset = here - src_start;

		strncpy(dest_start, src_start, offset);
		dest_start += offset;
		src_start += offset;

		strcpy(dest_start, new_token);
		dest_start += nlen;
		src_start += olen;

		strcpy(dest_start, src_start);	/* remainder of string */
		here = cpumask_find_token(src_start, old_token);
	}
}

/**
 * cpulist_parse - extract a cpumask from a user string of ranges
 * @buf: the buffer to extract from
 * @dstp: the cpumask to set.
 *
 * Returns -errno, or 0 for success.
 *
 * Marked __ref because memblock_*() are __meminit and we use them for
 * any early calls before slab is available.
 */
int __ref cpulist_parse(const char *buf, struct cpumask *dstp)
{
	int r;
	char *cpulist, last_cpu[5];	/* NR_CPUS <= 9999 */
	size_t len = strlen(buf) + 1;	/* don't forget '\0' */
	bool early = !slab_is_available();

	if (!strcmp(buf, "all")) {
		cpumask_setall(dstp);
		return 0;
	}

	if (!strcmp(buf, "none")) {
		cpumask_clear(dstp);
		return 0;
	}

	/*
	 * strlen("last") means "len" is OK up to NR_CPUS <= 9999.
	 */
	if (early)
		cpulist = memblock_alloc(len, SMP_CACHE_BYTES);
	else
		cpulist = kzalloc(len, GFP_KERNEL);

	if (cpulist == NULL)
		return -ENOMEM;

	/*
	 * bitmap_parselist has no concept of "last" CPU, so we have to
	 * replace "last" with a real number in dest copy of the string.
	 */
	sprintf(last_cpu, "%d", cpumask_last(cpu_present_mask));
	cpulist_replace_token(cpulist, buf, "last", last_cpu);

	r = bitmap_parselist(cpulist, cpumask_bits(dstp), nr_cpumask_bits);

	if (early)
		memblock_free((phys_addr_t)cpulist, len);
	else
		kfree(cpulist);

	return r;
}
EXPORT_SYMBOL(cpulist_parse);

/* These are not inline because of header tangles. */
#ifdef CONFIG_CPUMASK_OFFSTACK
/**
 * alloc_cpumask_var_node - allocate a struct cpumask on a given node
 * @mask: pointer to cpumask_var_t where the cpumask is returned
 * @flags: GFP_ flags
 *
 * Only defined when CONFIG_CPUMASK_OFFSTACK=y, otherwise is
 * a nop returning a constant 1 (in <linux/cpumask.h>)
 * Returns TRUE if memory allocation succeeded, FALSE otherwise.
 *
 * In addition, mask will be NULL if this fails.  Note that gcc is
 * usually smart enough to know that mask can never be NULL if
 * CONFIG_CPUMASK_OFFSTACK=n, so does code elimination in that case
 * too.
 */
bool alloc_cpumask_var_node(cpumask_var_t *mask, gfp_t flags, int node)
{
	*mask = kmalloc_node(cpumask_size(), flags, node);

#ifdef CONFIG_DEBUG_PER_CPU_MAPS
	if (!*mask) {
		printk(KERN_ERR "=> alloc_cpumask_var: failed!\n");
		dump_stack();
	}
#endif

	return *mask != NULL;
}
EXPORT_SYMBOL(alloc_cpumask_var_node);

bool zalloc_cpumask_var_node(cpumask_var_t *mask, gfp_t flags, int node)
{
	return alloc_cpumask_var_node(mask, flags | __GFP_ZERO, node);
}
EXPORT_SYMBOL(zalloc_cpumask_var_node);

/**
 * alloc_cpumask_var - allocate a struct cpumask
 * @mask: pointer to cpumask_var_t where the cpumask is returned
 * @flags: GFP_ flags
 *
 * Only defined when CONFIG_CPUMASK_OFFSTACK=y, otherwise is
 * a nop returning a constant 1 (in <linux/cpumask.h>).
 *
 * See alloc_cpumask_var_node.
 */
bool alloc_cpumask_var(cpumask_var_t *mask, gfp_t flags)
{
	return alloc_cpumask_var_node(mask, flags, NUMA_NO_NODE);
}
EXPORT_SYMBOL(alloc_cpumask_var);

bool zalloc_cpumask_var(cpumask_var_t *mask, gfp_t flags)
{
	return alloc_cpumask_var(mask, flags | __GFP_ZERO);
}
EXPORT_SYMBOL(zalloc_cpumask_var);

/**
 * alloc_bootmem_cpumask_var - allocate a struct cpumask from the bootmem arena.
 * @mask: pointer to cpumask_var_t where the cpumask is returned
 *
 * Only defined when CONFIG_CPUMASK_OFFSTACK=y, otherwise is
 * a nop (in <linux/cpumask.h>).
 * Either returns an allocated (zero-filled) cpumask, or causes the
 * system to panic.
 */
void __init alloc_bootmem_cpumask_var(cpumask_var_t *mask)
{
	*mask = memblock_alloc(cpumask_size(), SMP_CACHE_BYTES);
	if (!*mask)
		panic("%s: Failed to allocate %u bytes\n", __func__,
		      cpumask_size());
}

/**
 * free_cpumask_var - frees memory allocated for a struct cpumask.
 * @mask: cpumask to free
 *
 * This is safe on a NULL mask.
 */
void free_cpumask_var(cpumask_var_t mask)
{
	kfree(mask);
}
EXPORT_SYMBOL(free_cpumask_var);

/**
 * free_bootmem_cpumask_var - frees result of alloc_bootmem_cpumask_var
 * @mask: cpumask to free
 */
void __init free_bootmem_cpumask_var(cpumask_var_t mask)
{
	memblock_free_early(__pa(mask), cpumask_size());
}
#endif

/**
 * cpumask_local_spread - select the i'th cpu with local numa cpu's first
 * @i: index number
 * @node: local numa_node
 *
 * This function selects an online CPU according to a numa aware policy;
 * local cpus are returned first, followed by non-local ones, then it
 * wraps around.
 *
 * It's not very efficient, but useful for setup.
 */
unsigned int cpumask_local_spread(unsigned int i, int node)
{
	int cpu, hk_flags;
	const struct cpumask *mask;

	hk_flags = HK_FLAG_DOMAIN | HK_FLAG_MANAGED_IRQ;
	mask = housekeeping_cpumask(hk_flags);
	/* Wrap: we always want a cpu. */
	i %= cpumask_weight(mask);

	if (node == NUMA_NO_NODE) {
		for_each_cpu(cpu, mask) {
			if (i-- == 0)
				return cpu;
		}
	} else {
		/* NUMA first. */
		for_each_cpu_and(cpu, cpumask_of_node(node), mask) {
			if (i-- == 0)
				return cpu;
		}

		for_each_cpu(cpu, mask) {
			/* Skip NUMA nodes, done above. */
			if (cpumask_test_cpu(cpu, cpumask_of_node(node)))
				continue;

			if (i-- == 0)
				return cpu;
		}
	}
	BUG();
}
EXPORT_SYMBOL(cpumask_local_spread);

static DEFINE_PER_CPU(int, distribute_cpu_mask_prev);

/**
 * Returns an arbitrary cpu within srcp1 & srcp2.
 *
 * Iterated calls using the same srcp1 and srcp2 will be distributed within
 * their intersection.
 *
 * Returns >= nr_cpu_ids if the intersection is empty.
 */
int cpumask_any_and_distribute(const struct cpumask *src1p,
			       const struct cpumask *src2p)
{
	int next, prev;

	/* NOTE: our first selection will skip 0. */
	prev = __this_cpu_read(distribute_cpu_mask_prev);

	next = cpumask_next_and(prev, src1p, src2p);
	if (next >= nr_cpu_ids)
		next = cpumask_first_and(src1p, src2p);

	if (next < nr_cpu_ids)
		__this_cpu_write(distribute_cpu_mask_prev, next);

	return next;
}
EXPORT_SYMBOL(cpumask_any_and_distribute);