x86/topology: Update the 'cpu cores' field in /proc/cpuinfo correctly across CPU...

[cris-mirror.git] / drivers / infiniband / hw / hfi1 / affinity.c

/*
 * Copyright(c) 2015 - 2017 Intel Corporation.
 *
 * This file is provided under a dual BSD/GPLv2 license.  When using or
 * redistributing this file, you may do so under either license.
 *
 * GPL LICENSE SUMMARY
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of version 2 of the GNU General Public License as
 * published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * BSD LICENSE
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 *  - Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *  - Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 *  - Neither the name of Intel Corporation nor the names of its
 *    contributors may be used to endorse or promote products derived
 *    from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 */
#include <linux/topology.h>
#include <linux/cpumask.h>
#include <linux/module.h>
#include <linux/interrupt.h>

#include "hfi.h"
#include "affinity.h"
#include "sdma.h"
#include "trace.h"

struct hfi1_affinity_node_list node_affinity = {
        .list = LIST_HEAD_INIT(node_affinity.list),
        .lock = __MUTEX_INITIALIZER(node_affinity.lock)
};

/* Name of IRQ types, indexed by enum irq_type */
static const char * const irq_type_names[] = {
        "SDMA",
        "RCVCTXT",
        "GENERAL",
        "OTHER",
};

/* Per NUMA node count of HFI devices */
static unsigned int *hfi1_per_node_cntr;

static inline void init_cpu_mask_set(struct cpu_mask_set *set)
{
        cpumask_clear(&set->mask);
        cpumask_clear(&set->used);
        set->gen = 0;
}

/* Initialize non-HT cpu cores mask */
void init_real_cpu_mask(void)
{
        int possible, curr_cpu, i, ht;

        cpumask_clear(&node_affinity.real_cpu_mask);

        /* Start with cpu online mask as the real cpu mask */
        cpumask_copy(&node_affinity.real_cpu_mask, cpu_online_mask);

        /*
         * Remove HT cores from the real cpu mask.  Do this in two steps below.
         */
        possible = cpumask_weight(&node_affinity.real_cpu_mask);
        ht = cpumask_weight(topology_sibling_cpumask(
                                cpumask_first(&node_affinity.real_cpu_mask)));
        /*
         * Step 1.  Skip over the first N HT siblings and use them as the
         * "real" cores.  Assumes that HT cores are not enumerated in
         * succession (except in the single core case).
         */
        curr_cpu = cpumask_first(&node_affinity.real_cpu_mask);
        for (i = 0; i < possible / ht; i++)
                curr_cpu = cpumask_next(curr_cpu, &node_affinity.real_cpu_mask);
        /*
         * Step 2.  Remove the remaining HT siblings.  Use cpumask_next() to
         * skip any gaps.
         */
        for (; i < possible; i++) {
                cpumask_clear_cpu(curr_cpu, &node_affinity.real_cpu_mask);
                curr_cpu = cpumask_next(curr_cpu, &node_affinity.real_cpu_mask);
        }
}

int node_affinity_init(void)
{
        int node;
        struct pci_dev *dev = NULL;
        const struct pci_device_id *ids = hfi1_pci_tbl;

        cpumask_clear(&node_affinity.proc.used);
        cpumask_copy(&node_affinity.proc.mask, cpu_online_mask);

        node_affinity.proc.gen = 0;
        node_affinity.num_core_siblings =
                                cpumask_weight(topology_sibling_cpumask(
                                        cpumask_first(&node_affinity.proc.mask)
                                        ));
        node_affinity.num_possible_nodes = num_possible_nodes();
        node_affinity.num_online_nodes = num_online_nodes();
        node_affinity.num_online_cpus = num_online_cpus();

        /*
         * The real cpu mask is part of the affinity struct but it has to be
         * initialized early. It is needed to calculate the number of user
         * contexts in set_up_context_variables().
         */
        init_real_cpu_mask();

        hfi1_per_node_cntr = kcalloc(node_affinity.num_possible_nodes,
                                     sizeof(*hfi1_per_node_cntr), GFP_KERNEL);
        if (!hfi1_per_node_cntr)
                return -ENOMEM;

        while (ids->vendor) {
                dev = NULL;
                while ((dev = pci_get_device(ids->vendor, ids->device, dev))) {
                        node = pcibus_to_node(dev->bus);
                        if (node < 0)
                                node = numa_node_id();

                        hfi1_per_node_cntr[node]++;
                }
                ids++;
        }

        return 0;
}

void node_affinity_destroy(void)
{
        struct list_head *pos, *q;
        struct hfi1_affinity_node *entry;

        mutex_lock(&node_affinity.lock);
        list_for_each_safe(pos, q, &node_affinity.list) {
                entry = list_entry(pos, struct hfi1_affinity_node,
                                   list);
                list_del(pos);
                kfree(entry);
        }
        mutex_unlock(&node_affinity.lock);
        kfree(hfi1_per_node_cntr);
}

static struct hfi1_affinity_node *node_affinity_allocate(int node)
{
        struct hfi1_affinity_node *entry;

        entry = kzalloc(sizeof(*entry), GFP_KERNEL);
        if (!entry)
                return NULL;
        entry->node = node;
        INIT_LIST_HEAD(&entry->list);

        return entry;
}

/*
 * It appends an entry to the list.
 * It *must* be called with node_affinity.lock held.
 */
static void node_affinity_add_tail(struct hfi1_affinity_node *entry)
{
        list_add_tail(&entry->list, &node_affinity.list);
}

/* It must be called with node_affinity.lock held */
static struct hfi1_affinity_node *node_affinity_lookup(int node)
{
        struct list_head *pos;
        struct hfi1_affinity_node *entry;

        list_for_each(pos, &node_affinity.list) {
                entry = list_entry(pos, struct hfi1_affinity_node, list);
                if (entry->node == node)
                        return entry;
        }

        return NULL;
}

/*
 * Interrupt affinity.
 *
 * non-rcv avail gets a default mask that
 * starts as possible cpus with threads reset
 * and each rcv avail reset.
 *
 * rcv avail gets node relative 1 wrapping back
 * to the node relative 1 as necessary.
 *
 */
int hfi1_dev_affinity_init(struct hfi1_devdata *dd)
{
        int node = pcibus_to_node(dd->pcidev->bus);
        struct hfi1_affinity_node *entry;
        const struct cpumask *local_mask;
        int curr_cpu, possible, i;

        if (node < 0)
                node = numa_node_id();
        dd->node = node;

        local_mask = cpumask_of_node(dd->node);
        if (cpumask_first(local_mask) >= nr_cpu_ids)
                local_mask = topology_core_cpumask(0);

        mutex_lock(&node_affinity.lock);
        entry = node_affinity_lookup(dd->node);

        /*
         * If this is the first time this NUMA node's affinity is used,
         * create an entry in the global affinity structure and initialize it.
         */
        if (!entry) {
                entry = node_affinity_allocate(node);
                if (!entry) {
                        dd_dev_err(dd,
                                   "Unable to allocate global affinity node\n");
                        mutex_unlock(&node_affinity.lock);
                        return -ENOMEM;
                }
                init_cpu_mask_set(&entry->def_intr);
                init_cpu_mask_set(&entry->rcv_intr);
                cpumask_clear(&entry->general_intr_mask);
                /* Use the "real" cpu mask of this node as the default */
                cpumask_and(&entry->def_intr.mask, &node_affinity.real_cpu_mask,
                            local_mask);

                /* fill in the receive list */
                possible = cpumask_weight(&entry->def_intr.mask);
                curr_cpu = cpumask_first(&entry->def_intr.mask);

                if (possible == 1) {
                        /* only one CPU, everyone will use it */
                        cpumask_set_cpu(curr_cpu, &entry->rcv_intr.mask);
                        cpumask_set_cpu(curr_cpu, &entry->general_intr_mask);
                } else {
                        /*
                         * The general/control context will be the first CPU in
                         * the default list, so it is removed from the default
                         * list and added to the general interrupt list.
                         */
                        cpumask_clear_cpu(curr_cpu, &entry->def_intr.mask);
                        cpumask_set_cpu(curr_cpu, &entry->general_intr_mask);
                        curr_cpu = cpumask_next(curr_cpu,
                                                &entry->def_intr.mask);

                        /*
                         * Remove the remaining kernel receive queues from
                         * the default list and add them to the receive list.
                         */
                        for (i = 0;
                             i < (dd->n_krcv_queues - 1) *
                                  hfi1_per_node_cntr[dd->node];
                             i++) {
                                cpumask_clear_cpu(curr_cpu,
                                                  &entry->def_intr.mask);
                                cpumask_set_cpu(curr_cpu,
                                                &entry->rcv_intr.mask);
                                curr_cpu = cpumask_next(curr_cpu,
                                                        &entry->def_intr.mask);
                                if (curr_cpu >= nr_cpu_ids)
                                        break;
                        }

                        /*
                         * If there ends up being 0 CPU cores leftover for SDMA
                         * engines, use the same CPU cores as general/control
                         * context.
                         */
                        if (cpumask_weight(&entry->def_intr.mask) == 0)
                                cpumask_copy(&entry->def_intr.mask,
                                             &entry->general_intr_mask);
                }

                node_affinity_add_tail(entry);
        }
        mutex_unlock(&node_affinity.lock);
        return 0;
}

/*
 * Function updates the irq affinity hint for msix after it has been changed
 * by the user using the /proc/irq interface. This function only accepts
 * one cpu in the mask.
 */
static void hfi1_update_sdma_affinity(struct hfi1_msix_entry *msix, int cpu)
{
        struct sdma_engine *sde = msix->arg;
        struct hfi1_devdata *dd = sde->dd;
        struct hfi1_affinity_node *entry;
        struct cpu_mask_set *set;
        int i, old_cpu;

        if (cpu > num_online_cpus() || cpu == sde->cpu)
                return;

        mutex_lock(&node_affinity.lock);
        entry = node_affinity_lookup(dd->node);
        if (!entry)
                goto unlock;

        old_cpu = sde->cpu;
        sde->cpu = cpu;
        cpumask_clear(&msix->mask);
        cpumask_set_cpu(cpu, &msix->mask);
        dd_dev_dbg(dd, "IRQ: %u, type %s engine %u -> cpu: %d\n",
                   msix->irq, irq_type_names[msix->type],
                   sde->this_idx, cpu);
        irq_set_affinity_hint(msix->irq, &msix->mask);

        /*
         * Set the new cpu in the hfi1_affinity_node and clean
         * the old cpu if it is not used by any other IRQ
         */
        set = &entry->def_intr;
        cpumask_set_cpu(cpu, &set->mask);
        cpumask_set_cpu(cpu, &set->used);
        for (i = 0; i < dd->num_msix_entries; i++) {
                struct hfi1_msix_entry *other_msix;

                other_msix = &dd->msix_entries[i];
                if (other_msix->type != IRQ_SDMA || other_msix == msix)
                        continue;

                if (cpumask_test_cpu(old_cpu, &other_msix->mask))
                        goto unlock;
        }
        cpumask_clear_cpu(old_cpu, &set->mask);
        cpumask_clear_cpu(old_cpu, &set->used);
unlock:
        mutex_unlock(&node_affinity.lock);
}

static void hfi1_irq_notifier_notify(struct irq_affinity_notify *notify,
                                     const cpumask_t *mask)
{
        int cpu = cpumask_first(mask);
        struct hfi1_msix_entry *msix = container_of(notify,
                                                    struct hfi1_msix_entry,
                                                    notify);

        /* Only one CPU configuration supported currently */
        hfi1_update_sdma_affinity(msix, cpu);
}

static void hfi1_irq_notifier_release(struct kref *ref)
{
        /*
         * This is required by affinity notifier. We don't have anything to
         * free here.
         */
}

static void hfi1_setup_sdma_notifier(struct hfi1_msix_entry *msix)
{
        struct irq_affinity_notify *notify = &msix->notify;

        notify->irq = msix->irq;
        notify->notify = hfi1_irq_notifier_notify;
        notify->release = hfi1_irq_notifier_release;

        if (irq_set_affinity_notifier(notify->irq, notify))
                pr_err("Failed to register sdma irq affinity notifier for irq %d\n",
                       notify->irq);
}

static void hfi1_cleanup_sdma_notifier(struct hfi1_msix_entry *msix)
{
        struct irq_affinity_notify *notify = &msix->notify;

        if (irq_set_affinity_notifier(notify->irq, NULL))
                pr_err("Failed to cleanup sdma irq affinity notifier for irq %d\n",
                       notify->irq);
}

/*
 * Function sets the irq affinity for msix.
 * It *must* be called with node_affinity.lock held.
 */
static int get_irq_affinity(struct hfi1_devdata *dd,
                            struct hfi1_msix_entry *msix)
{
        int ret;
        cpumask_var_t diff;
        struct hfi1_affinity_node *entry;
        struct cpu_mask_set *set = NULL;
        struct sdma_engine *sde = NULL;
        struct hfi1_ctxtdata *rcd = NULL;
        char extra[64];
        int cpu = -1;

        extra[0] = '\0';
        cpumask_clear(&msix->mask);

        ret = zalloc_cpumask_var(&diff, GFP_KERNEL);
        if (!ret)
                return -ENOMEM;

        entry = node_affinity_lookup(dd->node);

        switch (msix->type) {
        case IRQ_SDMA:
                sde = (struct sdma_engine *)msix->arg;
                scnprintf(extra, 64, "engine %u", sde->this_idx);
                set = &entry->def_intr;
                break;
        case IRQ_GENERAL:
                cpu = cpumask_first(&entry->general_intr_mask);
                break;
        case IRQ_RCVCTXT:
                rcd = (struct hfi1_ctxtdata *)msix->arg;
                if (rcd->ctxt == HFI1_CTRL_CTXT)
                        cpu = cpumask_first(&entry->general_intr_mask);
                else
                        set = &entry->rcv_intr;
                scnprintf(extra, 64, "ctxt %u", rcd->ctxt);
                break;
        default:
                dd_dev_err(dd, "Invalid IRQ type %d\n", msix->type);
                return -EINVAL;
        }

        /*
         * The general and control contexts are placed on a particular
         * CPU, which is set above. Skip accounting for it. Everything else
         * finds its CPU here.
         */
        if (cpu == -1 && set) {
                if (cpumask_equal(&set->mask, &set->used)) {
                        /*
                         * We've used up all the CPUs, bump up the generation
                         * and reset the 'used' map
                         */
                        set->gen++;
                        cpumask_clear(&set->used);
                }
                cpumask_andnot(diff, &set->mask, &set->used);
                cpu = cpumask_first(diff);
                cpumask_set_cpu(cpu, &set->used);
        }

        cpumask_set_cpu(cpu, &msix->mask);
        dd_dev_info(dd, "IRQ: %u, type %s %s -> cpu: %d\n",
                    msix->irq, irq_type_names[msix->type],
                    extra, cpu);
        irq_set_affinity_hint(msix->irq, &msix->mask);

        if (msix->type == IRQ_SDMA) {
                sde->cpu = cpu;
                hfi1_setup_sdma_notifier(msix);
        }

        free_cpumask_var(diff);
        return 0;
}

int hfi1_get_irq_affinity(struct hfi1_devdata *dd, struct hfi1_msix_entry *msix)
{
        int ret;

        mutex_lock(&node_affinity.lock);
        ret = get_irq_affinity(dd, msix);
        mutex_unlock(&node_affinity.lock);
        return ret;
}

void hfi1_put_irq_affinity(struct hfi1_devdata *dd,
                           struct hfi1_msix_entry *msix)
{
        struct cpu_mask_set *set = NULL;
        struct hfi1_ctxtdata *rcd;
        struct hfi1_affinity_node *entry;

        mutex_lock(&node_affinity.lock);
        entry = node_affinity_lookup(dd->node);

        switch (msix->type) {
        case IRQ_SDMA:
                set = &entry->def_intr;
                hfi1_cleanup_sdma_notifier(msix);
                break;
        case IRQ_GENERAL:
                /* Don't do accounting for general contexts */
                break;
        case IRQ_RCVCTXT:
                rcd = (struct hfi1_ctxtdata *)msix->arg;
                /* Don't do accounting for control contexts */
                if (rcd->ctxt != HFI1_CTRL_CTXT)
                        set = &entry->rcv_intr;
                break;
        default:
                mutex_unlock(&node_affinity.lock);
                return;
        }

        if (set) {
                cpumask_andnot(&set->used, &set->used, &msix->mask);
                if (cpumask_empty(&set->used) && set->gen) {
                        set->gen--;
                        cpumask_copy(&set->used, &set->mask);
                }
        }

        irq_set_affinity_hint(msix->irq, NULL);
        cpumask_clear(&msix->mask);
        mutex_unlock(&node_affinity.lock);
}

/* This should be called with node_affinity.lock held */
static void find_hw_thread_mask(uint hw_thread_no, cpumask_var_t hw_thread_mask,
                                struct hfi1_affinity_node_list *affinity)
{
        int possible, curr_cpu, i;
        uint num_cores_per_socket = node_affinity.num_online_cpus /
                                        affinity->num_core_siblings /
                                                node_affinity.num_online_nodes;

        cpumask_copy(hw_thread_mask, &affinity->proc.mask);
        if (affinity->num_core_siblings > 0) {
                /* Removing other siblings not needed for now */
                possible = cpumask_weight(hw_thread_mask);
                curr_cpu = cpumask_first(hw_thread_mask);
                for (i = 0;
                     i < num_cores_per_socket * node_affinity.num_online_nodes;
                     i++)
                        curr_cpu = cpumask_next(curr_cpu, hw_thread_mask);

                for (; i < possible; i++) {
                        cpumask_clear_cpu(curr_cpu, hw_thread_mask);
                        curr_cpu = cpumask_next(curr_cpu, hw_thread_mask);
                }

                /* Identifying correct HW threads within physical cores */
                cpumask_shift_left(hw_thread_mask, hw_thread_mask,
                                   num_cores_per_socket *
                                   node_affinity.num_online_nodes *
                                   hw_thread_no);
        }
}

int hfi1_get_proc_affinity(int node)
{
        int cpu = -1, ret, i;
        struct hfi1_affinity_node *entry;
        cpumask_var_t diff, hw_thread_mask, available_mask, intrs_mask;
        const struct cpumask *node_mask,
                *proc_mask = &current->cpus_allowed;
        struct hfi1_affinity_node_list *affinity = &node_affinity;
        struct cpu_mask_set *set = &affinity->proc;

        /*
         * check whether process/context affinity has already
         * been set
         */
        if (cpumask_weight(proc_mask) == 1) {
                hfi1_cdbg(PROC, "PID %u %s affinity set to CPU %*pbl",
                          current->pid, current->comm,
                          cpumask_pr_args(proc_mask));
                /*
                 * Mark the pre-set CPU as used. This is atomic so we don't
                 * need the lock
                 */
                cpu = cpumask_first(proc_mask);
                cpumask_set_cpu(cpu, &set->used);
                goto done;
        } else if (cpumask_weight(proc_mask) < cpumask_weight(&set->mask)) {
                hfi1_cdbg(PROC, "PID %u %s affinity set to CPU set(s) %*pbl",
                          current->pid, current->comm,
                          cpumask_pr_args(proc_mask));
                goto done;
        }

        /*
         * The process does not have a preset CPU affinity so find one to
         * recommend using the following algorithm:
         *
         * For each user process that is opening a context on HFI Y:
         *  a) If all cores are filled, reinitialize the bitmask
         *  b) Fill real cores first, then HT cores (First set of HT
         *     cores on all physical cores, then second set of HT core,
         *     and, so on) in the following order:
         *
         *     1. Same NUMA node as HFI Y and not running an IRQ
         *        handler
         *     2. Same NUMA node as HFI Y and running an IRQ handler
         *     3. Different NUMA node to HFI Y and not running an IRQ
         *        handler
         *     4. Different NUMA node to HFI Y and running an IRQ
         *        handler
         *  c) Mark core as filled in the bitmask. As user processes are
         *     done, clear cores from the bitmask.
         */

        ret = zalloc_cpumask_var(&diff, GFP_KERNEL);
        if (!ret)
                goto done;
        ret = zalloc_cpumask_var(&hw_thread_mask, GFP_KERNEL);
        if (!ret)
                goto free_diff;
        ret = zalloc_cpumask_var(&available_mask, GFP_KERNEL);
        if (!ret)
                goto free_hw_thread_mask;
        ret = zalloc_cpumask_var(&intrs_mask, GFP_KERNEL);
        if (!ret)
                goto free_available_mask;

        mutex_lock(&affinity->lock);
        /*
         * If we've used all available HW threads, clear the mask and start
         * overloading.
         */
        if (cpumask_equal(&set->mask, &set->used)) {
                set->gen++;
                cpumask_clear(&set->used);
        }

        /*
         * If NUMA node has CPUs used by interrupt handlers, include them in the
         * interrupt handler mask.
         */
        entry = node_affinity_lookup(node);
        if (entry) {
                cpumask_copy(intrs_mask, (entry->def_intr.gen ?
                                          &entry->def_intr.mask :
                                          &entry->def_intr.used));
                cpumask_or(intrs_mask, intrs_mask, (entry->rcv_intr.gen ?
                                                    &entry->rcv_intr.mask :
                                                    &entry->rcv_intr.used));
                cpumask_or(intrs_mask, intrs_mask, &entry->general_intr_mask);
        }
        hfi1_cdbg(PROC, "CPUs used by interrupts: %*pbl",
                  cpumask_pr_args(intrs_mask));

        cpumask_copy(hw_thread_mask, &set->mask);

        /*
         * If HT cores are enabled, identify which HW threads within the
         * physical cores should be used.
         */
        if (affinity->num_core_siblings > 0) {
                for (i = 0; i < affinity->num_core_siblings; i++) {
                        find_hw_thread_mask(i, hw_thread_mask, affinity);

                        /*
                         * If there's at least one available core for this HW
                         * thread number, stop looking for a core.
                         *
                         * diff will always be not empty at least once in this
                         * loop as the used mask gets reset when
                         * (set->mask == set->used) before this loop.
                         */
                        cpumask_andnot(diff, hw_thread_mask, &set->used);
                        if (!cpumask_empty(diff))
                                break;
                }
        }
        hfi1_cdbg(PROC, "Same available HW thread on all physical CPUs: %*pbl",
                  cpumask_pr_args(hw_thread_mask));

        node_mask = cpumask_of_node(node);
        hfi1_cdbg(PROC, "Device on NUMA %u, CPUs %*pbl", node,
                  cpumask_pr_args(node_mask));

        /* Get cpumask of available CPUs on preferred NUMA */
        cpumask_and(available_mask, hw_thread_mask, node_mask);
        cpumask_andnot(available_mask, available_mask, &set->used);
        hfi1_cdbg(PROC, "Available CPUs on NUMA %u: %*pbl", node,
                  cpumask_pr_args(available_mask));

        /*
         * At first, we don't want to place processes on the same
         * CPUs as interrupt handlers. Then, CPUs running interrupt
         * handlers are used.
         *
         * 1) If diff is not empty, then there are CPUs not running
         *    non-interrupt handlers available, so diff gets copied
         *    over to available_mask.
         * 2) If diff is empty, then all CPUs not running interrupt
         *    handlers are taken, so available_mask contains all
         *    available CPUs running interrupt handlers.
         * 3) If available_mask is empty, then all CPUs on the
         *    preferred NUMA node are taken, so other NUMA nodes are
         *    used for process assignments using the same method as
         *    the preferred NUMA node.
         */
        cpumask_andnot(diff, available_mask, intrs_mask);
        if (!cpumask_empty(diff))
                cpumask_copy(available_mask, diff);

        /* If we don't have CPUs on the preferred node, use other NUMA nodes */
        if (cpumask_empty(available_mask)) {
                cpumask_andnot(available_mask, hw_thread_mask, &set->used);
                /* Excluding preferred NUMA cores */
                cpumask_andnot(available_mask, available_mask, node_mask);
                hfi1_cdbg(PROC,
                          "Preferred NUMA node cores are taken, cores available in other NUMA nodes: %*pbl",
                          cpumask_pr_args(available_mask));

                /*
                 * At first, we don't want to place processes on the same
                 * CPUs as interrupt handlers.
                 */
                cpumask_andnot(diff, available_mask, intrs_mask);
                if (!cpumask_empty(diff))
                        cpumask_copy(available_mask, diff);
        }
        hfi1_cdbg(PROC, "Possible CPUs for process: %*pbl",
                  cpumask_pr_args(available_mask));

        cpu = cpumask_first(available_mask);
        if (cpu >= nr_cpu_ids) /* empty */
                cpu = -1;
        else
                cpumask_set_cpu(cpu, &set->used);

        mutex_unlock(&affinity->lock);
        hfi1_cdbg(PROC, "Process assigned to CPU %d", cpu);

        free_cpumask_var(intrs_mask);
free_available_mask:
        free_cpumask_var(available_mask);
free_hw_thread_mask:
        free_cpumask_var(hw_thread_mask);
free_diff:
        free_cpumask_var(diff);
done:
        return cpu;
}

void hfi1_put_proc_affinity(int cpu)
{
        struct hfi1_affinity_node_list *affinity = &node_affinity;
        struct cpu_mask_set *set = &affinity->proc;

        if (cpu < 0)
                return;

        mutex_lock(&affinity->lock);
        cpumask_clear_cpu(cpu, &set->used);
        hfi1_cdbg(PROC, "Returning CPU %d for future process assignment", cpu);
        if (cpumask_empty(&set->used) && set->gen) {
                set->gen--;
                cpumask_copy(&set->used, &set->mask);
        }
        mutex_unlock(&affinity->lock);
}