tools/perf/util/cgroup.c

   1 #include "util.h"
   2 #include "../perf.h"
   3 #include <subcmd/parse-options.h>
   4 #include "evsel.h"
   5 #include "cgroup.h"
   6 #include "evlist.h"
   7 #include <linux/stringify.h>
   8
   9 int nr_cgroups;
  10
  11 static int
  12 cgroupfs_find_mountpoint(char *buf, size_t maxlen)
  13 {
  14         FILE *fp;
  15         char mountpoint[PATH_MAX + 1], tokens[PATH_MAX + 1], type[PATH_MAX + 1];
  16         char path_v1[PATH_MAX + 1], path_v2[PATH_MAX + 2], *path;
  17         char *token, *saved_ptr = NULL;
  18
  19         fp = fopen("/proc/mounts", "r");
  20         if (!fp)
  21                 return -1;
  22
  23         /*
  24          * in order to handle split hierarchy, we need to scan /proc/mounts
  25          * and inspect every cgroupfs mount point to find one that has
  26          * perf_event subsystem
  27          */
  28         path_v1[0] = '\0';
  29         path_v2[0] = '\0';
  30
  31         while (fscanf(fp, "%*s %"__stringify(PATH_MAX)"s %"__stringify(PATH_MAX)"s %"
  32                                 __stringify(PATH_MAX)"s %*d %*d\n",
  33                                 mountpoint, type, tokens) == 3) {
  34
  35                 if (!path_v1[0] && !strcmp(type, "cgroup")) {
  36
  37                         token = strtok_r(tokens, ",", &saved_ptr);
  38
  39                         while (token != NULL) {
  40                                 if (!strcmp(token, "perf_event")) {
  41                                         strcpy(path_v1, mountpoint);
  42                                         break;
  43                                 }
  44                                 token = strtok_r(NULL, ",", &saved_ptr);
  45                         }
  46                 }
  47
  48                 if (!path_v2[0] && !strcmp(type, "cgroup2"))
  49                         strcpy(path_v2, mountpoint);
  50
  51                 if (path_v1[0] && path_v2[0])
  52                         break;
  53         }
  54         fclose(fp);
  55
  56         if (path_v1[0])
  57                 path = path_v1;
  58         else if (path_v2[0])
  59                 path = path_v2;
  60         else
  61                 return -1;
  62
  63         if (strlen(path) < maxlen) {
  64                 strcpy(buf, path);
  65                 return 0;
  66         }
  67         return -1;
  68 }
  69
  70 static int open_cgroup(char *name)
  71 {
  72         char path[PATH_MAX + 1];
  73         char mnt[PATH_MAX + 1];
  74         int fd;
  75
  76
  77         if (cgroupfs_find_mountpoint(mnt, PATH_MAX + 1))
  78                 return -1;
  79
  80         snprintf(path, PATH_MAX, "%s/%s", mnt, name);
  81
  82         fd = open(path, O_RDONLY);
  83         if (fd == -1)
  84                 fprintf(stderr, "no access to cgroup %s\n", path);
  85
  86         return fd;
  87 }
  88
  89 static int add_cgroup(struct perf_evlist *evlist, char *str)
  90 {
  91         struct perf_evsel *counter;
  92         struct cgroup_sel *cgrp = NULL;
  93         int n;
  94         /*
  95          * check if cgrp is already defined, if so we reuse it
  96          */
  97         evlist__for_each_entry(evlist, counter) {
  98                 cgrp = counter->cgrp;
  99                 if (!cgrp)
 100                         continue;
 101                 if (!strcmp(cgrp->name, str))
 102                         break;
 103
 104                 cgrp = NULL;
 105         }
 106
 107         if (!cgrp) {
 108                 cgrp = zalloc(sizeof(*cgrp));
 109                 if (!cgrp)
 110                         return -1;
 111
 112                 cgrp->name = str;
 113
 114                 cgrp->fd = open_cgroup(str);
 115                 if (cgrp->fd == -1) {
 116                         free(cgrp);
 117                         return -1;
 118                 }
 119         }
 120
 121         /*
 122          * find corresponding event
 123          * if add cgroup N, then need to find event N
 124          */
 125         n = 0;
 126         evlist__for_each_entry(evlist, counter) {
 127                 if (n == nr_cgroups)
 128                         goto found;
 129                 n++;
 130         }
 131         if (refcount_read(&cgrp->refcnt) == 0)
 132                 free(cgrp);
 133
 134         return -1;
 135 found:
 136         refcount_inc(&cgrp->refcnt);
 137         counter->cgrp = cgrp;
 138         return 0;
 139 }
 140
 141 void close_cgroup(struct cgroup_sel *cgrp)
 142 {
 143         if (cgrp && refcount_dec_and_test(&cgrp->refcnt)) {
 144                 close(cgrp->fd);
 145                 zfree(&cgrp->name);
 146                 free(cgrp);
 147         }
 148 }
 149
 150 int parse_cgroups(const struct option *opt __maybe_unused, const char *str,
 151                   int unset __maybe_unused)
 152 {
 153         struct perf_evlist *evlist = *(struct perf_evlist **)opt->value;
 154         const char *p, *e, *eos = str + strlen(str);
 155         char *s;
 156         int ret;
 157
 158         if (list_empty(&evlist->entries)) {
 159                 fprintf(stderr, "must define events before cgroups\n");
 160                 return -1;
 161         }
 162
 163         for (;;) {
 164                 p = strchr(str, ',');
 165                 e = p ? p : eos;
 166
 167                 /* allow empty cgroups, i.e., skip */
 168                 if (e - str) {
 169                         /* termination added */
 170                         s = strndup(str, e - str);
 171                         if (!s)
 172                                 return -1;
 173                         ret = add_cgroup(evlist, s);
 174                         if (ret) {
 175                                 free(s);
 176                                 return -1;
 177                         }
 178                 }
 179                 /* nr_cgroups is increased een for empty cgroups */
 180                 nr_cgroups++;
 181                 if (!p)
 182                         break;
 183                 str = p+1;
 184         }
 185         return 0;
 186 }