proc_cpuview: release lock before returning

[mirror_lxcfs.git] / src / proc_cpuview.c

/* SPDX-License-Identifier: LGPL-2.1+ */

#ifndef _GNU_SOURCE
#define _GNU_SOURCE
#endif

#include "config.h"

#ifdef HAVE_FUSE3
#ifndef FUSE_USE_VERSION
#define FUSE_USE_VERSION 30
#endif
#else
#ifndef FUSE_USE_VERSION
#define FUSE_USE_VERSION 26
#endif
#endif

#define _FILE_OFFSET_BITS 64

#define __STDC_FORMAT_MACROS
#include <dirent.h>
#include <errno.h>
#include <fcntl.h>
#include <fuse.h>
#include <inttypes.h>
#include <libgen.h>
#include <pthread.h>
#include <sched.h>
#include <stdarg.h>
#include <stdbool.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
#include <unistd.h>
#include <wait.h>
#include <linux/magic.h>
#include <linux/sched.h>
#include <sys/epoll.h>
#include <sys/mman.h>
#include <sys/mount.h>
#include <sys/param.h>
#include <sys/socket.h>
#include <sys/syscall.h>
#include <sys/sysinfo.h>
#include <sys/vfs.h>

#include "bindings.h"
#include "cgroup_fuse.h"
#include "cpuset_parse.h"
#include "cgroups/cgroup.h"
#include "cgroups/cgroup_utils.h"
#include "memory_utils.h"
#include "proc_loadavg.h"
#include "utils.h"

/* Data for CPU view */
struct cg_proc_stat {
        char *cg;
        struct cpuacct_usage *usage;    /* Real usage as read from the host's /proc/stat. */
        struct cpuacct_usage *view;     /* Usage stats reported to the container. */
        int cpu_count;
        pthread_mutex_t lock;           /* For node manipulation. */
        struct cg_proc_stat *next;
};

struct cg_proc_stat_head {
        struct cg_proc_stat *next;
        time_t lastcheck;

        /*
         * For access to the list. Reading can be parallel, pruning is exclusive.
         */
        pthread_rwlock_t lock;
};

#define CPUVIEW_HASH_SIZE 100
static struct cg_proc_stat_head *proc_stat_history[CPUVIEW_HASH_SIZE];

static void reset_proc_stat_node(struct cg_proc_stat *node,
                                 struct cpuacct_usage *usage, int cpu_count)
{
        lxcfs_debug("Resetting stat node for %s\n", node->cg);
        memcpy(node->usage, usage, sizeof(struct cpuacct_usage) * cpu_count);

        for (int i = 0; i < cpu_count; i++) {
                node->view[i].user = 0;
                node->view[i].system = 0;
                node->view[i].idle = 0;
        }

        node->cpu_count = cpu_count;
}

static bool expand_proc_stat_node(struct cg_proc_stat *node, int cpu_count)
{
        __do_free struct cpuacct_usage *new_usage = NULL, *new_view = NULL;

        /* Allocate new memory */
        new_usage = zalloc(sizeof(struct cpuacct_usage) * cpu_count);
        if (!new_usage)
                return false;

        new_view = zalloc(sizeof(struct cpuacct_usage) * cpu_count);
        if (!new_view)
                return false;

        /* Copy existing data & initialize new elements */
        for (int i = 0; i < cpu_count; i++) {
                if (i < node->cpu_count) {
                        new_usage[i].user       = node->usage[i].user;
                        new_usage[i].system     = node->usage[i].system;
                        new_usage[i].idle       = node->usage[i].idle;

                        new_view[i].user        = node->view[i].user;
                        new_view[i].system      = node->view[i].system;
                        new_view[i].idle        = node->view[i].idle;
                }
        }

        free(node->usage);
        node->usage = move_ptr(new_usage);

        free(node->view);
        node->view = move_ptr(new_view);
        node->cpu_count = cpu_count;

        return true;
}

static void free_proc_stat_node(struct cg_proc_stat *node)
{
        if (node) {
                /*
                 * We're abusing the usage pointer to indicate that
                 * pthread_mutex_init() was successful. Don't judge me.
                 */
                if (node->usage)
                        pthread_mutex_destroy(&node->lock);
                free_disarm(node->cg);
                free_disarm(node->usage);
                free_disarm(node->view);
                free_disarm(node);
        }
}

define_cleanup_function(struct cg_proc_stat *, free_proc_stat_node);

static struct cg_proc_stat *add_proc_stat_node(struct cg_proc_stat *new_node)
{
        call_cleaner(free_proc_stat_node) struct cg_proc_stat *new = new_node;
        struct cg_proc_stat *rv = new_node;
        int hash = calc_hash(new->cg) % CPUVIEW_HASH_SIZE;
        struct cg_proc_stat_head *head = proc_stat_history[hash];
        struct cg_proc_stat *cur;

        pthread_rwlock_wrlock(&head->lock);

        if (!head->next) {
                head->next = move_ptr(new);
                goto out_rwlock_unlock;
        }

        cur = head->next;

        for (;;) {
                /*
                 * The node to be added is already present in the list, so
                 * free the newly allocated one and return the one we found.
                 */
                if (strcmp(cur->cg, new->cg) == 0) {
                        rv = cur;
                        goto out_rwlock_unlock;
                }

                /* Keep walking. */
                if (cur->next) {
                        cur = cur->next;
                        continue;
                }

                /* Add new node to end of list. */
                cur->next = move_ptr(new);
                goto out_rwlock_unlock;
        }

out_rwlock_unlock:
        pthread_rwlock_unlock(&head->lock);
        return move_ptr(rv);
}

static struct cg_proc_stat *new_proc_stat_node(struct cpuacct_usage *usage,
                                               int cpu_count, const char *cg)
{
        call_cleaner(free_proc_stat_node) struct cg_proc_stat *node = NULL;
        __do_free struct cpuacct_usage *new_usage = NULL;

        node = zalloc(sizeof(struct cg_proc_stat));
        if (!node)
                return NULL;

        node->cg = strdup(cg);
        if (!node->cg)
                return NULL;

        new_usage = memdup(usage, sizeof(struct cpuacct_usage) * cpu_count);
        if (!new_usage)
                return NULL;

        node->view = zalloc(sizeof(struct cpuacct_usage) * cpu_count);
        if (!node->view)
                return NULL;

        node->cpu_count = cpu_count;

        if (pthread_mutex_init(&node->lock, NULL))
                return NULL;
        /*
         * We're abusing the usage pointer to indicate that
         * pthread_mutex_init() was successful. Don't judge me.
         */
        node->usage = move_ptr(new_usage);

        return move_ptr(node);
}

static bool cgroup_supports(const char *controller, const char *cgroup,
                            const char *file)
{
        __do_free char *path = NULL;
        int cfd;

        cfd = get_cgroup_fd(controller);
        if (cfd < 0)
                return false;

        path = must_make_path_relative(cgroup, file, NULL);
        return faccessat(cfd, path, F_OK, 0) == 0;
}

static struct cg_proc_stat *prune_proc_stat_list(struct cg_proc_stat *node)
{
        struct cg_proc_stat *first = NULL;

        for (struct cg_proc_stat *prev = NULL; node; ) {
                if (!cgroup_supports("cpu", node->cg, "cpu.shares")) {
                        call_cleaner(free_proc_stat_node) struct cg_proc_stat *cur = node;

                        if (prev)
                                prev->next = node->next;
                        else
                                first = node->next;

                        node = node->next;
                        lxcfs_debug("Removing stat node for %s\n", cur->cg);
                } else {
                        if (!first)
                                first = node;
                        prev = node;
                        node = node->next;
                }
        }

        return first;
}

#define PROC_STAT_PRUNE_INTERVAL 10
static void prune_proc_stat_history(void)
{
        time_t now = time(NULL);

        for (int i = 0; i < CPUVIEW_HASH_SIZE; i++) {
                pthread_rwlock_wrlock(&proc_stat_history[i]->lock);

                if ((proc_stat_history[i]->lastcheck + PROC_STAT_PRUNE_INTERVAL) > now) {
                        pthread_rwlock_unlock(&proc_stat_history[i]->lock);
                        return;
                }

                if (proc_stat_history[i]->next) {
                        proc_stat_history[i]->next = prune_proc_stat_list(proc_stat_history[i]->next);
                        proc_stat_history[i]->lastcheck = now;
                }

                pthread_rwlock_unlock(&proc_stat_history[i]->lock);
        }
}

static struct cg_proc_stat *find_proc_stat_node(struct cg_proc_stat_head *head,
                                                const char *cg)
{
        struct cg_proc_stat *node;

        pthread_rwlock_rdlock(&head->lock);

        if (!head->next) {
                pthread_rwlock_unlock(&head->lock);
                return NULL;
        }

        node = head->next;

        do {
                if (strcmp(cg, node->cg) == 0)
                        goto out;
        } while ((node = node->next));

        node = NULL;

out:
        pthread_rwlock_unlock(&head->lock);
        prune_proc_stat_history();
        return node;
}

static struct cg_proc_stat *find_or_create_proc_stat_node(struct cpuacct_usage *usage,
                                                          int cpu_count, const char *cg)
{
        int hash = calc_hash(cg) % CPUVIEW_HASH_SIZE;
        struct cg_proc_stat_head *head = proc_stat_history[hash];
        struct cg_proc_stat *node;

        node = find_proc_stat_node(head, cg);
        if (!node) {
                node = new_proc_stat_node(usage, cpu_count, cg);
                if (!node)
                        return NULL;

                node = add_proc_stat_node(node);
                lxcfs_debug("New stat node (%d) for %s\n", cpu_count, cg);
        }

        pthread_mutex_lock(&node->lock);

        /*
         * If additional CPUs on the host have been enabled, CPU usage counter
         * arrays have to be expanded.
         */
        if (node->cpu_count < cpu_count) {
                lxcfs_debug("Expanding stat node %d->%d for %s\n",
                            node->cpu_count, cpu_count, cg);

                if (!expand_proc_stat_node(node, cpu_count)) {
                        pthread_mutex_unlock(&node->lock);
                        return log_debug(NULL, "Unable to expand stat node %d->%d for %s", node->cpu_count, cpu_count, cg);
                }
        }

        return node;
}

static void add_cpu_usage(uint64_t *surplus, struct cpuacct_usage *usage,
                          uint64_t *counter, uint64_t threshold)
{
        uint64_t free_space, to_add;

        free_space = threshold - usage->user - usage->system;

        if (free_space > usage->idle)
                free_space = usage->idle;

        if (free_space > *surplus)
                to_add = *surplus;
        else
                to_add = free_space;

        *counter += to_add;
        usage->idle -= to_add;
        *surplus -= to_add;
}

static uint64_t diff_cpu_usage(struct cpuacct_usage *older,
                               struct cpuacct_usage *newer,
                               struct cpuacct_usage *diff, int cpu_count)
{
        uint64_t sum = 0;

        for (int i = 0; i < cpu_count; i++) {
                if (!newer[i].online)
                        continue;

                /*
                 * When cpuset is changed on the fly, the CPUs might get
                 * reordered. We could either reset all counters, or check
                 * that the substractions below will return expected results.
                 */
                if (newer[i].user > older[i].user)
                        diff[i].user = newer[i].user - older[i].user;
                else
                        diff[i].user = 0;

                if (newer[i].system > older[i].system)
                        diff[i].system = newer[i].system - older[i].system;
                else
                        diff[i].system = 0;

                if (newer[i].idle > older[i].idle)
                        diff[i].idle = newer[i].idle - older[i].idle;
                else
                        diff[i].idle = 0;

                sum += diff[i].user;
                sum += diff[i].system;
                sum += diff[i].idle;
        }

        return sum;
}

/*
 * Read cgroup CPU quota parameters from `cpu.cfs_quota_us` or
 * `cpu.cfs_period_us`, depending on `param`. Parameter value is returned
 * through `value`.
 */
static bool read_cpu_cfs_param(const char *cg, const char *param, int64_t *value)
{
        __do_free char *str = NULL;
        char file[STRLITERALLEN("cpu.cfs_period_us") + 1];
        bool first = true;
        int ret;

        if (pure_unified_layout(cgroup_ops)) {
                first = !strcmp(param, "quota");
                ret = snprintf(file, sizeof(file), "cpu.max");
        } else {
                ret = snprintf(file, sizeof(file), "cpu.cfs_%s_us", param);
        }
        if (ret < 0 || (size_t)ret >= sizeof(file))
                return false;

        if (!cgroup_ops->get(cgroup_ops, "cpu", cg, file, &str))
                return false;

        return sscanf(str, first ? "%" PRId64 : "%*d %" PRId64, value) == 1;
}

/*
 * Return the exact number of visible CPUs based on CPU quotas.
 * If there is no quota set, zero is returned.
 */
static double exact_cpu_count(const char *cg)
{
        double rv;
        int nprocs;
        int64_t cfs_quota, cfs_period;

        if (!read_cpu_cfs_param(cg, "quota", &cfs_quota))
                return 0;

        if (!read_cpu_cfs_param(cg, "period", &cfs_period))
                return 0;

        if (cfs_quota <= 0 || cfs_period <= 0)
                return 0;

        rv = (double)cfs_quota / (double)cfs_period;

        nprocs = get_nprocs();

        if (rv > nprocs)
                rv = nprocs;

        return rv;
}

/*
 * Return the maximum number of visible CPUs based on CPU quotas.
 * If there is no quota set, zero is returned.
 */
int max_cpu_count(const char *cg)
{
        __do_free char *cpuset = NULL;
        int rv, nprocs;
        int64_t cfs_quota, cfs_period;
        int nr_cpus_in_cpuset = 0;

        if (!read_cpu_cfs_param(cg, "quota", &cfs_quota))
                return 0;

        if (!read_cpu_cfs_param(cg, "period", &cfs_period))
                return 0;

        cpuset = get_cpuset(cg);
        if (cpuset)
                nr_cpus_in_cpuset = cpu_number_in_cpuset(cpuset);

        if (cfs_quota <= 0 || cfs_period <= 0) {
                if (nr_cpus_in_cpuset > 0)
                        return nr_cpus_in_cpuset;

                return 0;
        }

        rv = cfs_quota / cfs_period;

        /*
         * In case quota/period does not yield a whole number, add one CPU for
         * the remainder.
         */
        if ((cfs_quota % cfs_period) > 0)
                rv += 1;

        nprocs = get_nprocs();
        if (rv > nprocs)
                rv = nprocs;

        /* Use min value in cpu quota and cpuset. */
        if (nr_cpus_in_cpuset > 0 && nr_cpus_in_cpuset < rv)
                rv = nr_cpus_in_cpuset;

        return rv;
}

int cpuview_proc_stat(const char *cg, const char *cpuset,
                      struct cpuacct_usage *cg_cpu_usage, int cg_cpu_usage_size,
                      FILE *f, char *buf, size_t buf_size)
{
        __do_free char *line = NULL;
        __do_free struct cpuacct_usage *diff = NULL;
        size_t linelen = 0, total_len = 0;
        int curcpu = -1; /* cpu numbering starts at 0 */
        int physcpu, i;
        int cpu_cnt = 0;
        uint64_t user = 0, nice = 0, system = 0, idle = 0, iowait = 0, irq = 0,
                 softirq = 0, steal = 0, guest = 0, guest_nice = 0;
        uint64_t user_sum = 0, system_sum = 0, idle_sum = 0;
        uint64_t user_surplus = 0, system_surplus = 0;
        int nprocs, max_cpus;
        ssize_t l;
        uint64_t total_sum, threshold;
        struct cg_proc_stat *stat_node;

        nprocs = get_nprocs_conf();
        if (cg_cpu_usage_size < nprocs)
                nprocs = cg_cpu_usage_size;

        /* Read all CPU stats and stop when we've encountered other lines */
        while (getline(&line, &linelen, f) != -1) {
                int ret;
                char cpu_char[10]; /* That's a lot of cores */
                uint64_t all_used, cg_used;

                if (strlen(line) == 0)
                        continue;

                /* not a ^cpuN line containing a number N */
                if (sscanf(line, "cpu%9[^ ]", cpu_char) != 1)
                        break;

                if (sscanf(cpu_char, "%d", &physcpu) != 1)
                        continue;

                if (physcpu >= cg_cpu_usage_size)
                        continue;

                curcpu++;
                cpu_cnt++;

                if (!cpu_in_cpuset(physcpu, cpuset)) {
                        for (i = curcpu; i <= physcpu; i++)
                                cg_cpu_usage[i].online = false;
                        continue;
                }

                if (curcpu < physcpu) {
                        /* Some CPUs may be disabled */
                        for (i = curcpu; i < physcpu; i++)
                                cg_cpu_usage[i].online = false;

                        curcpu = physcpu;
                }

                cg_cpu_usage[curcpu].online = true;

                ret = sscanf(line, "%*s %" PRIu64 " %" PRIu64 " %" PRIu64 " %" PRIu64 " %" PRIu64 " %" PRIu64 " %" PRIu64 " %" PRIu64 " %" PRIu64 " %" PRIu64 "lu",
                           &user,
                           &nice,
                           &system,
                           &idle,
                           &iowait,
                           &irq,
                           &softirq,
                           &steal,
                           &guest,
                           &guest_nice);
                if (ret != 10)
                        continue;

                all_used = user + nice + system + iowait + irq + softirq + steal + guest + guest_nice;
                cg_used = cg_cpu_usage[curcpu].user + cg_cpu_usage[curcpu].system;

                if (all_used >= cg_used) {
                        cg_cpu_usage[curcpu].idle = idle + (all_used - cg_used);

                } else {
                        lxcfs_error("cpu%d from %s has unexpected cpu time: %" PRIu64 " in /proc/stat, %" PRIu64 " in cpuacct.usage_all; unable to determine idle time",
                                    curcpu, cg, all_used, cg_used);
                        cg_cpu_usage[curcpu].idle = idle;
                }
        }

        /* Cannot use more CPUs than is available in cpuset. */
        max_cpus = max_cpu_count(cg);
        if (max_cpus > cpu_cnt || !max_cpus)
                max_cpus = cpu_cnt;

        /* takes lock pthread_mutex_lock(&node->lock) */
        stat_node = find_or_create_proc_stat_node(cg_cpu_usage, nprocs, cg);
        if (!stat_node)
                return log_error(0, "Failed to find/create stat node for %s", cg);

        diff = zalloc(sizeof(struct cpuacct_usage) * nprocs);
        if (!diff)
                return 0;

        /*
         * If the new values are LOWER than values stored in memory, it means
         * the cgroup has been reset/recreated and we should reset too.
         */
        for (curcpu = 0; curcpu < nprocs; curcpu++) {
                if (!cg_cpu_usage[curcpu].online)
                        continue;

                if (cg_cpu_usage[curcpu].user < stat_node->usage[curcpu].user)
                        reset_proc_stat_node(stat_node, cg_cpu_usage, nprocs);

                break;
        }

        total_sum = diff_cpu_usage(stat_node->usage, cg_cpu_usage, diff, nprocs);

        for (curcpu = 0, i = -1; curcpu < nprocs; curcpu++) {
                stat_node->usage[curcpu].online = cg_cpu_usage[curcpu].online;

                if (!stat_node->usage[curcpu].online)
                        continue;

                i++;

                stat_node->usage[curcpu].user   += diff[curcpu].user;
                stat_node->usage[curcpu].system += diff[curcpu].system;
                stat_node->usage[curcpu].idle   += diff[curcpu].idle;

                if (max_cpus > 0 && i >= max_cpus) {
                        user_surplus    += diff[curcpu].user;
                        system_surplus  += diff[curcpu].system;
                }
        }

        /* Calculate usage counters of visible CPUs */
        if (max_cpus > 0) {
                uint64_t diff_user = 0;
                uint64_t diff_system = 0;
                uint64_t diff_idle = 0;
                uint64_t max_diff_idle = 0;
                uint64_t max_diff_idle_index = 0;
                double exact_cpus;

                /* threshold = maximum usage per cpu, including idle */
                threshold = total_sum / cpu_cnt * max_cpus;

                for (curcpu = 0, i = -1; curcpu < nprocs; curcpu++) {
                        if (!stat_node->usage[curcpu].online)
                                continue;

                        i++;

                        if (i == max_cpus)
                                break;

                        if (diff[curcpu].user + diff[curcpu].system >= threshold)
                                continue;

                        /* Add user */
                        add_cpu_usage(&user_surplus, &diff[curcpu],
                                      &diff[curcpu].user, threshold);

                        if (diff[curcpu].user + diff[curcpu].system >= threshold)
                                continue;

                        /* If there is still room, add system */
                        add_cpu_usage(&system_surplus, &diff[curcpu],
                                      &diff[curcpu].system, threshold);
                }

                if (user_surplus > 0)
                        lxcfs_debug("leftover user: %lu for %s\n", user_surplus, cg);
                if (system_surplus > 0)
                        lxcfs_debug("leftover system: %lu for %s\n", system_surplus, cg);

                for (curcpu = 0, i = -1; curcpu < nprocs; curcpu++) {
                        if (!stat_node->usage[curcpu].online)
                                continue;

                        i++;

                        if (i == max_cpus)
                                break;

                        stat_node->view[curcpu].user    += diff[curcpu].user;
                        stat_node->view[curcpu].system  += diff[curcpu].system;
                        stat_node->view[curcpu].idle    += diff[curcpu].idle;

                        user_sum        += stat_node->view[curcpu].user;
                        system_sum      += stat_node->view[curcpu].system;
                        idle_sum        += stat_node->view[curcpu].idle;

                        diff_user       += diff[curcpu].user;
                        diff_system     += diff[curcpu].system;
                        diff_idle       += diff[curcpu].idle;
                        if (diff[curcpu].idle > max_diff_idle) {
                                max_diff_idle           = diff[curcpu].idle;
                                max_diff_idle_index     = curcpu;
                        }

                        lxcfs_v("curcpu: %d, diff_user: %lu, diff_system: %lu, diff_idle: %lu\n", curcpu, diff[curcpu].user, diff[curcpu].system, diff[curcpu].idle);
                }
                lxcfs_v("total. diff_user: %lu, diff_system: %lu, diff_idle: %lu\n", diff_user, diff_system, diff_idle);

                /* revise cpu usage view to support partial cpu case. */
                exact_cpus = exact_cpu_count(cg);
                if (exact_cpus < (double)max_cpus){
                        uint64_t delta = (uint64_t)((double)(diff_user + diff_system + diff_idle) * (1 - exact_cpus / (double)max_cpus));

                        lxcfs_v("revising cpu usage view to match the exact cpu count [%f]\n", exact_cpus);
                        lxcfs_v("delta: %lu\n", delta);
                        lxcfs_v("idle_sum before: %lu\n", idle_sum);
                        if (idle_sum > delta)
                                idle_sum = idle_sum - delta;
                        else
                                idle_sum = 0;
                        lxcfs_v("idle_sum after: %lu\n", idle_sum);

                        curcpu = max_diff_idle_index;
                        lxcfs_v("curcpu: %d, idle before: %lu\n", curcpu, stat_node->view[curcpu].idle);
                        if (stat_node->view[curcpu].idle > delta)
                                stat_node->view[curcpu].idle = stat_node->view[curcpu].idle - delta;
                        else
                                stat_node->view[curcpu].idle = 0;
                        lxcfs_v("curcpu: %d, idle after: %lu\n", curcpu, stat_node->view[curcpu].idle);
                }
        } else {
                for (curcpu = 0; curcpu < nprocs; curcpu++) {
                        if (!stat_node->usage[curcpu].online)
                                continue;

                        stat_node->view[curcpu].user    = stat_node->usage[curcpu].user;
                        stat_node->view[curcpu].system  = stat_node->usage[curcpu].system;
                        stat_node->view[curcpu].idle    = stat_node->usage[curcpu].idle;

                        user_sum        += stat_node->view[curcpu].user;
                        system_sum      += stat_node->view[curcpu].system;
                        idle_sum        += stat_node->view[curcpu].idle;
                }
        }

        /* Render the file */
        /* cpu-all */
        l = snprintf(buf, buf_size,
                     "cpu  %" PRIu64 " 0 %" PRIu64 " %" PRIu64 " 0 0 0 0 0 0\n",
                     user_sum, system_sum, idle_sum);
        lxcfs_v("cpu-all: %s\n", buf);
        if (l < 0) {
                lxcfs_error("Failed to write cache");
                total_len = 0;
                goto out_pthread_mutex_unlock;
        }
        if (l >= buf_size)
                return log_error(0, "Write to cache was truncated");

        buf += l;
        buf_size -= l;
        total_len += l;

        /* Render visible CPUs */
        for (curcpu = 0, i = -1; curcpu < nprocs; curcpu++) {
                if (!stat_node->usage[curcpu].online)
                        continue;

                i++;

                if (max_cpus > 0 && i == max_cpus)
                        break;

                l = snprintf(buf, buf_size, "cpu%d %" PRIu64 " 0 %" PRIu64 " %" PRIu64 " 0 0 0 0 0 0\n",
                             i,
                             stat_node->view[curcpu].user,
                             stat_node->view[curcpu].system,
                             stat_node->view[curcpu].idle);
                lxcfs_v("cpu: %s\n", buf);
                if (l < 0) {
                        lxcfs_error("Failed to write cache");
                        total_len = 0;
                        goto out_pthread_mutex_unlock;
                }
                if (l >= buf_size) {
                        lxcfs_error("Write to cache was truncated");
                        total_len = 0;
                        goto out_pthread_mutex_unlock;
                }

                buf += l;
                buf_size -= l;
                total_len += l;
        }

        /* Pass the rest of /proc/stat, start with the last line read */
        l = snprintf(buf, buf_size, "%s", line);
        if (l < 0) {
                lxcfs_error("Failed to write cache");
                total_len = 0;
                goto out_pthread_mutex_unlock;
        }
        if (l >= buf_size) {
                lxcfs_error("Write to cache was truncated");
                total_len = 0;
                goto out_pthread_mutex_unlock;
        }

        buf += l;
        buf_size -= l;
        total_len += l;

        /* Pass the rest of the host's /proc/stat */
        while (getline(&line, &linelen, f) != -1) {
                l = snprintf(buf, buf_size, "%s", line);
                if (l < 0) {
                        lxcfs_error("Failed to write cache");
                        total_len = 0;
                        goto out_pthread_mutex_unlock;
                }
                if (l >= buf_size) {
                        lxcfs_error("Write to cache was truncated");
                        total_len = 0;
                        goto out_pthread_mutex_unlock;
                }

                buf += l;
                buf_size -= l;
                total_len += l;
        }

out_pthread_mutex_unlock:
        if (stat_node)
                pthread_mutex_unlock(&stat_node->lock);

        return total_len;
}

/*
 * check whether this is a '^processor" line in /proc/cpuinfo
 */
static inline bool is_processor_line(const char *line)
{
        int cpu;
        return sscanf(line, "processor       : %d", &cpu) == 1;
}

static inline bool cpuline_in_cpuset(const char *line, const char *cpuset)
{
        int cpu;

        if (sscanf(line, "processor       : %d", &cpu) == 1)
                return cpu_in_cpuset(cpu, cpuset);

        return false;
}

int proc_cpuinfo_read(char *buf, size_t size, off_t offset,
                      struct fuse_file_info *fi)
{
        __do_free char *cg = NULL, *cpuset = NULL, *line = NULL;
        __do_free void *fopen_cache = NULL;
        __do_fclose FILE *f = NULL;
        struct fuse_context *fc = fuse_get_context();
        struct lxcfs_opts *opts = (struct lxcfs_opts *)fc->private_data;
        struct file_info *d = INTTYPE_TO_PTR(fi->fh);
        size_t linelen = 0, total_len = 0;
        bool am_printing = false, firstline = true, is_s390x = false;
        int curcpu = -1, cpu, max_cpus = 0;
        bool use_view;
        char *cache = d->buf;
        size_t cache_size = d->buflen;

        if (offset) {
                int left;

                if (offset > d->size)
                        return -EINVAL;

                if (!d->cached)
                        return 0;

                left = d->size - offset;
                total_len = left > size ? size: left;
                memcpy(buf, cache + offset, total_len);

                return total_len;
        }

        pid_t initpid = lookup_initpid_in_store(fc->pid);
        if (initpid <= 1 || is_shared_pidns(initpid))
                initpid = fc->pid;

        cg = get_pid_cgroup(initpid, "cpuset");
        if (!cg)
                return read_file_fuse("proc/cpuinfo", buf, size, d);
        prune_init_slice(cg);

        cpuset = get_cpuset(cg);
        if (!cpuset)
                return 0;

        if (cgroup_ops->can_use_cpuview(cgroup_ops) && opts && opts->use_cfs)
                use_view = true;
        else
                use_view = false;
        if (use_view)
                max_cpus = max_cpu_count(cg);

        f = fopen_cached("/proc/cpuinfo", "re", &fopen_cache);
        if (!f)
                return 0;

        while (getline(&line, &linelen, f) != -1) {
                ssize_t l;
                if (firstline) {
                        firstline = false;
                        if (strstr(line, "IBM/S390") != NULL) {
                                is_s390x = true;
                                am_printing = true;
                                continue;
                        }
                }

                if (strncmp(line, "# processors:", 12) == 0)
                        continue;

                if (is_processor_line(line)) {
                        if (use_view && max_cpus > 0 && (curcpu + 1) == max_cpus)
                                break;

                        am_printing = cpuline_in_cpuset(line, cpuset);
                        if (am_printing) {
                                curcpu++;
                                l = snprintf(cache, cache_size, "processor      : %d\n", curcpu);
                                if (l < 0)
                                        return log_error(0, "Failed to write cache");
                                if (l >= cache_size)
                                        return log_error(0, "Write to cache was truncated");
                                cache += l;
                                cache_size -= l;
                                total_len += l;
                        }
                        continue;
                } else if (is_s390x && sscanf(line, "processor %d:", &cpu) == 1) {
                        char *p;

                        if (use_view && max_cpus > 0 && (curcpu + 1) == max_cpus)
                                break;

                        if (!cpu_in_cpuset(cpu, cpuset))
                                continue;

                        curcpu ++;
                        p = strchr(line, ':');
                        if (!p || !*p)
                                return 0;
                        p++;

                        l = snprintf(cache, cache_size, "processor %d:%s", curcpu, p);
                        if (l < 0)
                                return log_error(0, "Failed to write cache");
                        if (l >= cache_size)
                                return log_error(0, "Write to cache was truncated");

                        cache += l;
                        cache_size -= l;
                        total_len += l;
                        continue;

                }
                if (am_printing) {
                        l = snprintf(cache, cache_size, "%s", line);
                        if (l < 0)
                                return log_error(0, "Failed to write cache");
                        if (l >= cache_size)
                                return log_error(0, "Write to cache was truncated");

                        cache += l;
                        cache_size -= l;
                        total_len += l;
                }
        }

        if (is_s390x) {
                __do_free char *origcache = d->buf;
                ssize_t l;

                d->buf = malloc(d->buflen);
                if (!d->buf) {
                        d->buf = move_ptr(origcache);
                        return 0;
                }

                cache = d->buf;
                cache_size = d->buflen;
                total_len = 0;
                l = snprintf(cache, cache_size, "vendor_id       : IBM/S390\n");
                if (l < 0 || l >= cache_size)
                        return 0;

                cache_size -= l;
                cache += l;
                total_len += l;
                l = snprintf(cache, cache_size, "# processors    : %d\n", curcpu + 1);
                if (l < 0 || l >= cache_size)
                        return 0;

                cache_size -= l;
                cache += l;
                total_len += l;
                l = snprintf(cache, cache_size, "%s", origcache);
                if (l < 0 || l >= cache_size)
                        return 0;
                total_len += l;
        }

        d->cached = 1;
        d->size = total_len;
        if (total_len > size)
                total_len = size;

        /* read from off 0 */
        memcpy(buf, d->buf, total_len);

        return total_len;
}

/*
 * Returns 0 on success.
 * It is the caller's responsibility to free `return_usage`, unless this
 * function returns an error.
 */
int read_cpuacct_usage_all(char *cg, char *cpuset,
                           struct cpuacct_usage **return_usage, int *size)
{
        __do_free char *usage_str = NULL;
        __do_free struct cpuacct_usage *cpu_usage = NULL;
        int i = 0, j = 0, read_pos = 0, read_cnt = 0;
        int cpucount;
        int ret;
        int cg_cpu;
        uint64_t cg_user, cg_system;
        int64_t ticks_per_sec;

        ticks_per_sec = sysconf(_SC_CLK_TCK);
        if (ticks_per_sec < 0 && errno == EINVAL) {
                lxcfs_debug("%m - Failed to determine number of ticks per second");
                return -1;
        }

        cpucount = get_nprocs_conf();
        cpu_usage = malloc(sizeof(struct cpuacct_usage) * cpucount);
        if (!cpu_usage)
                return -ENOMEM;

        memset(cpu_usage, 0, sizeof(struct cpuacct_usage) * cpucount);
        if (!cgroup_ops->get(cgroup_ops, "cpuacct", cg, "cpuacct.usage_all", &usage_str)) {
                char *sep = " \t\n";
                char *tok;

                /* Read cpuacct.usage_percpu instead. */
                lxcfs_debug("Falling back to cpuacct.usage_percpu");
                if (!cgroup_ops->get(cgroup_ops, "cpuacct", cg, "cpuacct.usage_percpu", &usage_str))
                        return -1;

                lxc_iterate_parts(tok, usage_str, sep) {
                        uint64_t percpu_user;

                        if (i >= cpucount)
                                break;

                        tok = trim_whitespace_in_place(tok);
                        ret = safe_uint64(tok, &percpu_user, 10);
                        if (ret)
                                return -1;

                        /* Convert the time from nanoseconds to USER_HZ */
                        cpu_usage[i].user = percpu_user / 1000.0 / 1000 / 1000 * ticks_per_sec;
                        cpu_usage[i].system = cpu_usage[i].user;
                        i++;
                        lxcfs_debug("cpu%d with time %s", i, tok);
                }
        } else {
                if (sscanf(usage_str, "cpu user system\n%n", &read_cnt) != 0)
                        return log_error(-1, "read_cpuacct_usage_all reading first line from %s/cpuacct.usage_all failed", cg);

                read_pos += read_cnt;

                for (i = 0, j = 0; i < cpucount; i++) {
                        ret = sscanf(usage_str + read_pos,
                                        "%d %" PRIu64 " %" PRIu64 "\n%n", &cg_cpu,
                                        &cg_user, &cg_system, &read_cnt);

                        if (ret == EOF)
                                break;

                        if (ret != 3)
                                return log_error(-EINVAL, "Failed to parse cpuacct.usage_all line %s from cgroup %s",
                                                usage_str + read_pos, cg);

                        read_pos += read_cnt;

                        /* Convert the time from nanoseconds to USER_HZ */
                        cpu_usage[j].user = cg_user / 1000.0 / 1000 / 1000 * ticks_per_sec;
                        cpu_usage[j].system = cg_system / 1000.0 / 1000 / 1000 * ticks_per_sec;
                        j++;
                }
        }

        *return_usage = move_ptr(cpu_usage);
        *size = cpucount;
        return 0;
}

static bool cpuview_init_head(struct cg_proc_stat_head **head)
{
        __do_free struct cg_proc_stat_head *h;

        h = zalloc(sizeof(struct cg_proc_stat_head));
        if (!h)
                return false;

        if (pthread_rwlock_init(&h->lock, NULL))
                return false;

        h->lastcheck = time(NULL);

        *head = move_ptr(h);
        return true;
}

bool init_cpuview(void)
{
        int i;

        for (i = 0; i < CPUVIEW_HASH_SIZE; i++)
                proc_stat_history[i] = NULL;

        for (i = 0; i < CPUVIEW_HASH_SIZE; i++) {
                if (!cpuview_init_head(&proc_stat_history[i]))
                        goto err;
        }

        return true;

err:
        for (i = 0; i < CPUVIEW_HASH_SIZE; i++) {
                if (proc_stat_history[i])
                        free_disarm(proc_stat_history[i]);
        }

        return false;
}

static void cpuview_free_head(struct cg_proc_stat_head *head)
{
        struct cg_proc_stat *node;

        if (head->next) {
                node = head->next;

                for (;;) {
                        struct cg_proc_stat *cur = node;
                        node = node->next;
                        free_proc_stat_node(cur);
                        if (!node)
                                break;
                }
        }

        pthread_rwlock_destroy(&head->lock);
        free_disarm(head);
}

void free_cpuview(void)
{
        for (int i = 0; i < CPUVIEW_HASH_SIZE; i++)
                if (proc_stat_history[i])
                        cpuview_free_head(proc_stat_history[i]);
}