// SPDX-License-Identifier: GPL-2.0
#include <linux/slab.h>
#include <linux/kernel.h>
#include <linux/bitops.h>
#include <linux/cpumask.h>
#include <linux/export.h>
#include <linux/memblock.h>
#include <linux/numa.h>
/**
* 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
*
* Return: >= nr_cpu_ids on completion
*
* Note: the @wrap argument is required for the start condition when
* we cannot assume @start is set in @mask.
*/
unsigned int cpumask_next_wrap(int n, const struct cpumask *mask, int start, bool wrap)
{
unsigned 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);
/* 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
* @node: memory node from which to allocate or %NUMA_NO_NODE
*
* Only defined when CONFIG_CPUMASK_OFFSTACK=y, otherwise is
* a nop returning a constant 1 (in <linux/cpumask.h>).
*
* Return: 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);
/**
* 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(mask, cpumask_size());
}
#endif
/**
* cpumask_local_spread - select the i'th cpu based on NUMA distances
* @i: index number
* @node: local numa_node
*
* Return: online CPU according to a numa aware policy; local cpus are returned
* first, followed by non-local ones, then it wraps around.
*
* For those who wants to enumerate all CPUs based on their NUMA distances,
* i.e. call this function in a loop, like:
*
* for (i = 0; i < num_online_cpus(); i++) {
* cpu = cpumask_local_spread(i, node);
* do_something(cpu);
* }
*
* There's a better alternative based on for_each()-like iterators:
*
* for_each_numa_hop_mask(mask, node) {
* for_each_cpu_andnot(cpu, mask, prev)
* do_something(cpu);
* prev = mask;
* }
*
* It's simpler and more verbose than above. Complexity of iterator-based
* enumeration is O(sched_domains_numa_levels * nr_cpu_ids), while
* cpumask_local_spread() when called for each cpu is
* O(sched_domains_numa_levels * nr_cpu_ids * log(nr_cpu_ids)).
*/
unsigned int cpumask_local_spread(unsigned int i, int node)
{
unsigned int cpu;
/* Wrap: we always want a cpu. */
i %= num_online_cpus();
cpu = sched_numa_find_nth_cpu(cpu_online_mask, i, node);
WARN_ON(cpu >= nr_cpu_ids);
return cpu;
}
EXPORT_SYMBOL(cpumask_local_spread);
static DEFINE_PER_CPU(int, distribute_cpu_mask_prev);
/**
* cpumask_any_and_distribute - Return an arbitrary cpu within src1p & src2p.
* @src1p: first &cpumask for intersection
* @src2p: second &cpumask for intersection
*
* Iterated calls using the same srcp1 and srcp2 will be distributed within
* their intersection.
*
* Return: >= nr_cpu_ids if the intersection is empty.
*/
unsigned int cpumask_any_and_distribute(const struct cpumask *src1p,
const struct cpumask *src2p)
{
unsigned int next, prev;
/* NOTE: our first selection will skip 0. */
prev = __this_cpu_read(distribute_cpu_mask_prev);
next = find_next_and_bit_wrap(cpumask_bits(src1p), cpumask_bits(src2p),
nr_cpumask_bits, prev + 1);
if (next < nr_cpu_ids)
__this_cpu_write(distribute_cpu_mask_prev, next);
return next;
}
EXPORT_SYMBOL(cpumask_any_and_distribute);
/**
* cpumask_any_distribute - Return an arbitrary cpu from srcp
* @srcp: &cpumask for selection
*
* Return: >= nr_cpu_ids if the intersection is empty.
*/
unsigned int cpumask_any_distribute(const struct cpumask *srcp)
{
unsigned int next, prev;
/* NOTE: our first selection will skip 0. */
prev = __this_cpu_read(distribute_cpu_mask_prev);
next = find_next_bit_wrap(cpumask_bits(srcp), nr_cpumask_bits, prev + 1);
if (next < nr_cpu_ids)
__this_cpu_write(distribute_cpu_mask_prev, next);
return next;
}
EXPORT_SYMBOL(cpumask_any_distribute);
Codebase Browser
linux