Systemd/src/cgroup-util.c

/*-*- Mode: C; c-basic-offset: 8 -*-*/

/***
  This file is part of systemd.

  Copyright 2010 Lennart Poettering

  systemd is free software; you can redistribute it and/or modify it
  under the terms of the GNU General Public License as published by
  the Free Software Foundation; either version 2 of the License, or
  (at your option) any later version.

  systemd 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.

  You should have received a copy of the GNU General Public License
  along with systemd; If not, see <http://www.gnu.org/licenses/>.
***/

#include <errno.h>
#include <unistd.h>
#include <signal.h>
#include <string.h>
#include <stdlib.h>

#include <libcgroup.h>

#include "cgroup-util.h"
#include "log.h"
#include "set.h"
#include "macro.h"
#include "util.h"

/*
   Currently, the only remaining functionality from libcgroup we call
   here is:

   - cgroup_get_subsys_mount_point()
   - cgroup_walk_tree_begin()/cgroup_walk_tree_next()
   - cgroup_delete_cgroup_ext()
 */

int cg_translate_error(int error, int _errno) {

        switch (error) {

        case ECGROUPNOTCOMPILED:
        case ECGROUPNOTMOUNTED:
        case ECGROUPNOTEXIST:
        case ECGROUPNOTCREATED:
                return -ENOENT;

        case ECGINVAL:
                return -EINVAL;

        case ECGROUPNOTALLOWED:
                return -EPERM;

        case ECGOTHER:
                return -_errno;
        }

        return -EIO;
}

static struct cgroup* cg_new(const char *controller, const char *path) {
        struct cgroup *cgroup;

        assert(path);
        assert(controller);

        if (!(cgroup = cgroup_new_cgroup(path)))
                return NULL;

        if (!cgroup_add_controller(cgroup, controller)) {
                cgroup_free(&cgroup);
                return NULL;
        }

        return cgroup;
}

int cg_enumerate_processes(const char *controller, const char *path, FILE **_f) {
        char *fs;
        int r;
        FILE *f;

        assert(controller);
        assert(path);
        assert(_f);

        if ((r = cg_get_path(controller, path, "cgroup.procs", &fs)) < 0)
                return r;

        f = fopen(fs, "re");
        free(fs);

        if (!f)
                return -errno;

        *_f = f;
        return 0;
}

int cg_enumerate_tasks(const char *controller, const char *path, FILE **_f) {
        char *fs;
        int r;
        FILE *f;

        assert(controller);
        assert(path);
        assert(_f);

        if ((r = cg_get_path(controller, path, "tasks", &fs)) < 0)
                return r;

        f = fopen(fs, "re");
        free(fs);

        if (!f)
                return -errno;

        *_f = f;
        return 0;
}

int cg_read_pid(FILE *f, pid_t *_pid) {
        unsigned long ul;

        /* Note that the cgroup.procs might contain duplicates! See
         * cgroups.txt for details. */

        errno = 0;
        if (fscanf(f, "%lu", &ul) != 1) {

                if (feof(f))
                        return 0;

                return errno ? -errno : -EIO;
        }

        if (ul <= 0)
                return -EIO;

        *_pid = (pid_t) ul;
        return 1;
}

int cg_kill(const char *controller, const char *path, int sig, bool ignore_self) {
        bool killed = false, done = false;
        Set *s;
        pid_t my_pid;
        int r, ret = 0;
        FILE *f = NULL;

        assert(controller);
        assert(path);
        assert(sig >= 0);

        /* This goes through the tasks list and kills them all. This
         * is repeated until no further processes are added to the
         * tasks list, to properly handle forking processes */

        if (!(s = set_new(trivial_hash_func, trivial_compare_func)))
                return -ENOMEM;

        my_pid = getpid();

        do {
                pid_t pid;
                done = true;

                if ((r = cg_enumerate_processes(controller, path, &f)) < 0)
                        goto finish;

                while ((r = cg_read_pid(f, &pid)) > 0) {

                        if (pid == my_pid && ignore_self)
                                continue;

                        if (set_get(s, LONG_TO_PTR(pid)) == LONG_TO_PTR(pid))
                                continue;

                        /* If we haven't killed this process yet, kill
                         * it */
                        if (kill(pid, sig) < 0 && errno != ESRCH) {
                                if (ret == 0)
                                        ret = -errno;
                        }

                        killed = true;
                        done = false;

                        if ((r = set_put(s, LONG_TO_PTR(pid))) < 0)
                                break;
                }

                fclose(f);
                f = NULL;

                /* To avoid racing against processes which fork
                 * quicker than we can kill them we repeat this until
                 * no new pids need to be killed. */

        } while (!done && r >= 0);

finish:
        set_free(s);

        if (f)
                fclose(f);

        if (r < 0)
                return r;

        if (ret < 0)
                return ret;

        return !!killed;
}

int cg_kill_recursive(const char *controller, const char *path, int sig, bool ignore_self) {
        struct cgroup_file_info info;
        int level = 0, r, ret = 0;
        void *iterator = NULL;
        bool killed = false;

        assert(path);
        assert(controller);
        assert(sig >= 0);

        zero(info);

        r = cgroup_walk_tree_begin(controller, path, 0, &iterator, &info, &level);
        while (r == 0) {
                int k;
                char *p;

                if (info.type != CGROUP_FILE_TYPE_DIR)
                        goto next;

                if (asprintf(&p, "%s/%s", path, info.path) < 0) {
                        ret = -ENOMEM;
                        break;
                }

                k = cg_kill(controller, p, sig, ignore_self);
                free(p);

                if (k < 0) {
                        if (ret == 0)
                                ret = k;
                } else if (k > 0)
                        killed = true;

        next:

                r = cgroup_walk_tree_next(0, &iterator, &info, level);
        }

        if (ret == 0) {
                if (r == 0 || r == ECGEOF)
                        ret = !!killed;
                else if (r == ECGOTHER && errno == ENOENT)
                        ret = -ESRCH;
                else
                        ret = cg_translate_error(r, errno);
        }

        assert_se(cgroup_walk_tree_end(&iterator) == 0);

        return ret;
}

int cg_kill_recursive_and_wait(const char *controller, const char *path) {
        unsigned i;

        assert(path);
        assert(controller);

        /* This safely kills all processes; first it sends a SIGTERM,
         * then checks 8 times after 50ms whether the group is
         * now empty, and finally kills everything that is left with
         * SIGKILL */

        for (i = 0; i < 10; i++) {
                int sig, r;

                if (i <= 0)
                        sig = SIGTERM;
                else if (i >= 9)
                        sig = SIGKILL;
                else
                        sig = 0;

                if ((r = cg_kill_recursive(controller, path, sig, true)) <= 0)
                        return r;

                usleep(50 * USEC_PER_MSEC);
        }

        return 0;
}

int cg_migrate(const char *controller, const char *from, const char *to, bool ignore_self) {
        bool migrated = false, done = false;
        int r, ret = 0;
        pid_t my_pid;
        FILE *f = NULL;

        assert(controller);
        assert(from);
        assert(to);

        my_pid = getpid();

        do {
                pid_t pid;
                done = true;

                if ((r = cg_enumerate_tasks(controller, from, &f)) < 0)
                        goto finish;

                while ((r = cg_read_pid(f, &pid)) > 0) {

                        if (pid == my_pid && ignore_self)
                                continue;

                        if ((r = cg_attach(controller, to, pid)) < 0) {
                                if (ret == 0)
                                        ret = -r;
                        }

                        migrated = true;
                        done = false;
                }

                fclose(f);
                f = NULL;

        } while (!done && r >= 0);

finish:

        if (f)
                fclose(f);

        if (r < 0)
                return r;

        if (ret < 0)
                return ret;

        return !!migrated;
}

int cg_migrate_recursive(const char *controller, const char *from, const char *to, bool ignore_self) {
        struct cgroup_file_info info;
        int level = 0, r, ret = 0;
        void *iterator = NULL;
        bool migrated = false;

        assert(controller);
        assert(from);
        assert(to);

        zero(info);

        r = cgroup_walk_tree_begin(controller, from, 0, &iterator, &info, &level);
        while (r == 0) {
                int k;
                char *p;

                if (info.type != CGROUP_FILE_TYPE_DIR)
                        goto next;

                if (asprintf(&p, "%s/%s", from, info.path) < 0) {
                        ret = -ENOMEM;
                        break;
                }

                k = cg_migrate(controller, p, to, ignore_self);
                free(p);

                if (k < 0) {
                        if (ret == 0)
                                ret = k;
                } else if (k > 0)
                        migrated = true;

        next:
                r = cgroup_walk_tree_next(0, &iterator, &info, level);
        }

        if (ret == 0) {
                if (r == 0 || r == ECGEOF)
                        r = !!migrated;
                else if (r == ECGOTHER && errno == ENOENT)
                        r = -ESRCH;
                else
                        r = cg_translate_error(r, errno);
        }

        assert_se(cgroup_walk_tree_end(&iterator) == 0);

        return ret;
}

int cg_get_path(const char *controller, const char *path, const char *suffix, char **fs) {
        char *mp;
        int r;

        assert(controller);

        if ((r = cgroup_get_subsys_mount_point(controller, &mp)) != 0)
                return cg_translate_error(r, errno);

        if (path && suffix)
                r = asprintf(fs, "%s/%s/%s", mp, path, suffix);
        else if (path)
                r = asprintf(fs, "%s/%s", mp, path);
        else if (suffix)
                r = asprintf(fs, "%s/%s", mp, suffix);
        else {
                path_kill_slashes(mp);
                *fs = mp;
                return 0;
        }

        free(mp);
        path_kill_slashes(*fs);
        return r < 0 ? -ENOMEM : 0;
}

int cg_trim(const char *controller, const char *path, bool delete_root) {
        char *fs;
        int r;

        assert(controller);
        assert(path);

        if ((r = cg_get_path(controller, path, NULL, &fs)) < 0)
                return r;

        r = rm_rf(fs, true, delete_root);
        free(fs);

        return r;
}

int cg_delete(const char *controller, const char *path) {
        struct cgroup *cg;
        int r;

        assert(controller);
        assert(path);

        if (!(cg = cg_new(controller, path)))
                return -ENOMEM;

        if ((r = cgroup_delete_cgroup_ext(cg, CGFLAG_DELETE_RECURSIVE|CGFLAG_DELETE_IGNORE_MIGRATION)) != 0) {
                r = cg_translate_error(r, errno);
                goto finish;
        }

        r = 0;

finish:
        cgroup_free(&cg);

        return r;
}

int cg_create(const char *controller, const char *path) {
        char *fs;
        int r;

        assert(controller);
        assert(path);

        if ((r = cg_get_path(controller, path, NULL, &fs)) < 0)
                return r;

        r = mkdir_p(fs, 0755);
        free(fs);

        return r;
}

int cg_attach(const char *controller, const char *path, pid_t pid) {
        char *fs;
        int r;
        char c[32];

        assert(controller);
        assert(path);
        assert(pid >= 0);

        if ((r = cg_get_path(controller, path, "tasks", &fs)) < 0)
                return r;

        if (pid == 0)
                pid = getpid();

        snprintf(c, sizeof(c), "%lu\n", (unsigned long) pid);
        char_array_0(c);

        r = write_one_line_file(fs, c);
        free(fs);

        return r;
}

int cg_create_and_attach(const char *controller, const char *path, pid_t pid) {
        int r;

        assert(controller);
        assert(path);
        assert(pid >= 0);

        if ((r = cg_create(controller, path)) < 0)
                return r;

        if ((r = cg_attach(controller, path, pid)) < 0)
                return r;

        /* This does not remove the cgroup on failure */

        return r;
}

int cg_set_group_access(const char *controller, const char *path, mode_t mode, uid_t uid, gid_t gid) {
        char *fs;
        int r;

        assert(controller);
        assert(path);

        if ((r = cg_get_path(controller, path, NULL, &fs)) < 0)
                return r;

        r = chmod_and_chown(fs, mode, uid, gid);
        free(fs);

        return r;
}

int cg_set_task_access(const char *controller, const char *path, mode_t mode, uid_t uid, gid_t gid) {
        char *fs;
        int r;

        assert(controller);
        assert(path);

        if ((r = cg_get_path(controller, path, "tasks", &fs)) < 0)
                return r;

        r = chmod_and_chown(fs, mode, uid, gid);
        free(fs);

        return r;
}

int cg_get_by_pid(const char *controller, pid_t pid, char **path) {
        int r;
        char *p = NULL;
        FILE *f;
        char *fs;
        size_t cs;

        assert(controller);
        assert(path);
        assert(pid >= 0);

        if (pid == 0)
                pid = getpid();

        if (asprintf(&fs, "/proc/%lu/cgroup", (unsigned long) pid) < 0)
                return -ENOMEM;

        f = fopen(fs, "re");
        free(fs);

        cs = strlen(controller);

        while (!feof(f)) {
                char line[LINE_MAX];
                char *l;

                errno = 0;
                if (!(fgets(line, sizeof(line), f))) {
                        if (feof(f))
                                break;

                        r = errno ? -errno : -EIO;
                        goto finish;
                }

                truncate_nl(line);

                if (!(l = strchr(line, ':')))
                        continue;

                l++;
                if (strncmp(l, controller, cs) != 0)
                        continue;

                if (l[cs] != ':')
                        continue;

                if (!(p = strdup(l + cs + 1))) {
                        r = -ENOMEM;
                        goto finish;
                }

                *path = p;
                r = 0;
                goto finish;
        }

        r = -ENOENT;

finish:
        fclose(f);

        return r;
}

int cg_install_release_agent(const char *controller, const char *agent) {
        char *fs = NULL, *contents = NULL, *line = NULL, *sc;
        int r;

        assert(controller);
        assert(agent);

        if ((r = cg_get_path(controller, NULL, "release_agent", &fs)) < 0)
                return r;

        if ((r = read_one_line_file(fs, &contents)) < 0)
                goto finish;

        sc = strstrip(contents);
        if (sc[0] == 0) {

                if (asprintf(&line, "%s\n", agent) < 0) {
                        r = -ENOMEM;
                        goto finish;
                }

                if ((r = write_one_line_file(fs, line)) < 0)
                        goto finish;

        } else if (!streq(sc, agent)) {
                r = -EEXIST;
                goto finish;
        }

        free(fs);
        fs = NULL;
        if ((r = cg_get_path(controller, NULL, "notify_on_release", &fs)) < 0) {
                r = -ENOMEM;
                goto finish;
        }

        free(contents);
        contents = NULL;
        if ((r = read_one_line_file(fs, &contents)) < 0)
                goto finish;

        sc = strstrip(contents);

        if (streq(sc, "0")) {
                if ((r = write_one_line_file(fs, "1\n")) < 0)
                        goto finish;

                r = 1;
        } else if (!streq(sc, "1")) {
                r = -EIO;
                goto finish;
        } else
                r = 0;

finish:
        free(fs);
        free(contents);
        free(line);

        return r;
}

int cg_is_empty(const char *controller, const char *path, bool ignore_self) {
        pid_t pid;
        int r;
        FILE *f;
        bool found = false;

        assert(controller);
        assert(path);

        if ((r = cg_enumerate_tasks(controller, path, &f)) < 0)
                return r;

        while ((r = cg_read_pid(f, &pid)) > 0) {

                if (ignore_self && pid == getpid())
                        continue;

                found = true;
                break;
        }

        fclose(f);

        if (r < 0)
                return r;

        return !found;
}

int cg_is_empty_recursive(const char *controller, const char *path, bool ignore_self) {
        struct cgroup_file_info info;
        int level = 0, r, ret = 0;
        void *iterator = NULL;
        bool empty = true;

        assert(controller);
        assert(path);

        zero(info);

        r = cgroup_walk_tree_begin(controller, path, 0, &iterator, &info, &level);
        while (r == 0) {
                int k;
                char *p;

                if (info.type != CGROUP_FILE_TYPE_DIR)
                        goto next;

                if (asprintf(&p, "%s/%s", path, info.path) < 0) {
                        ret = -ENOMEM;
                        break;
                }

                k = cg_is_empty(controller, p, ignore_self);
                free(p);

                if (k < 0) {
                        ret = k;
                        break;
                } else if (k == 0) {
                        empty = false;
                        break;
                }

        next:
                r = cgroup_walk_tree_next(0, &iterator, &info, level);
        }

        if (ret == 0) {
                if (r == 0 || r == ECGEOF)
                        ret = !!empty;
                else if (r == ECGOTHER && errno == ENOENT)
                        ret = -ESRCH;
                else
                        ret = cg_translate_error(r, errno);
        }

        assert_se(cgroup_walk_tree_end(&iterator) == 0);

        return ret;
}

int cg_init(void) {
        int r;

        if ((r = cgroup_init()) != 0)
                return cg_translate_error(r, errno);

        return 0;
}