tools/perf/util/comm.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 #include "comm.h"
   3 #include <errno.h>
   4 #include <string.h>
   5 #include <internal/rc_check.h>
   6 #include <linux/refcount.h>
   7 #include <linux/zalloc.h>
   8 #include "rwsem.h"
   9
  10 DECLARE_RC_STRUCT(comm_str) {
  11         refcount_t refcnt;
  12         char str[];
  13 };
  14
  15 static struct comm_strs {
  16         struct rw_semaphore lock;
  17         struct comm_str **strs;
  18         int num_strs;
  19         int capacity;
  20 } _comm_strs;
  21
  22 static void comm_strs__remove_if_last(struct comm_str *cs);
  23
  24 static void comm_strs__init(void)
  25 {
  26         init_rwsem(&_comm_strs.lock);
  27         _comm_strs.capacity = 16;
  28         _comm_strs.num_strs = 0;
  29         _comm_strs.strs = calloc(16, sizeof(*_comm_strs.strs));
  30 }
  31
  32 static struct comm_strs *comm_strs__get(void)
  33 {
  34         static pthread_once_t comm_strs_type_once = PTHREAD_ONCE_INIT;
  35
  36         pthread_once(&comm_strs_type_once, comm_strs__init);
  37
  38         return &_comm_strs;
  39 }
  40
  41 static refcount_t *comm_str__refcnt(struct comm_str *cs)
  42 {
  43         return &RC_CHK_ACCESS(cs)->refcnt;
  44 }
  45
  46 static const char *comm_str__str(const struct comm_str *cs)
  47 {
  48         return &RC_CHK_ACCESS(cs)->str[0];
  49 }
  50
  51 static struct comm_str *comm_str__get(struct comm_str *cs)
  52 {
  53         struct comm_str *result;
  54
  55         if (RC_CHK_GET(result, cs))
  56                 refcount_inc_not_zero(comm_str__refcnt(cs));
  57
  58         return result;
  59 }
  60
  61 static void comm_str__put(struct comm_str *cs)
  62 {
  63         if (!cs)
  64                 return;
  65
  66         if (refcount_dec_and_test(comm_str__refcnt(cs))) {
  67                 RC_CHK_FREE(cs);
  68         } else {
  69                 if (refcount_read(comm_str__refcnt(cs)) == 1)
  70                         comm_strs__remove_if_last(cs);
  71
  72                 RC_CHK_PUT(cs);
  73         }
  74 }
  75
  76 static struct comm_str *comm_str__new(const char *str)
  77 {
  78         struct comm_str *result = NULL;
  79         RC_STRUCT(comm_str) *cs;
  80
  81         cs = malloc(sizeof(*cs) + strlen(str) + 1);
  82         if (ADD_RC_CHK(result, cs)) {
  83                 refcount_set(comm_str__refcnt(result), 1);
  84                 strcpy(&cs->str[0], str);
  85         }
  86         return result;
  87 }
  88
  89 static int comm_str__search(const void *_key, const void *_member)
  90 {
  91         const char *key = _key;
  92         const struct comm_str *member = *(const struct comm_str * const *)_member;
  93
  94         return strcmp(key, comm_str__str(member));
  95 }
  96
  97 static void comm_strs__remove_if_last(struct comm_str *cs)
  98 {
  99         struct comm_strs *comm_strs = comm_strs__get();
 100
 101         down_write(&comm_strs->lock);
 102         /*
 103          * Are there only references from the array, if so remove the array
 104          * reference under the write lock so that we don't race with findnew.
 105          */
 106         if (refcount_read(comm_str__refcnt(cs)) == 1) {
 107                 struct comm_str **entry;
 108
 109                 entry = bsearch(comm_str__str(cs), comm_strs->strs, comm_strs->num_strs,
 110                                 sizeof(struct comm_str *), comm_str__search);
 111                 comm_str__put(*entry);
 112                 for (int i = entry - comm_strs->strs; i < comm_strs->num_strs - 1; i++)
 113                         comm_strs->strs[i] = comm_strs->strs[i + 1];
 114                 comm_strs->num_strs--;
 115         }
 116         up_write(&comm_strs->lock);
 117 }
 118
 119 static struct comm_str *__comm_strs__find(struct comm_strs *comm_strs, const char *str)
 120 {
 121         struct comm_str **result;
 122
 123         result = bsearch(str, comm_strs->strs, comm_strs->num_strs, sizeof(struct comm_str *),
 124                          comm_str__search);
 125
 126         if (!result)
 127                 return NULL;
 128
 129         return comm_str__get(*result);
 130 }
 131
 132 static struct comm_str *comm_strs__findnew(const char *str)
 133 {
 134         struct comm_strs *comm_strs = comm_strs__get();
 135         struct comm_str *result;
 136
 137         if (!comm_strs)
 138                 return NULL;
 139
 140         down_read(&comm_strs->lock);
 141         result = __comm_strs__find(comm_strs, str);
 142         up_read(&comm_strs->lock);
 143         if (result)
 144                 return result;
 145
 146         down_write(&comm_strs->lock);
 147         result = __comm_strs__find(comm_strs, str);
 148         if (!result) {
 149                 if (comm_strs->num_strs == comm_strs->capacity) {
 150                         struct comm_str **tmp;
 151
 152                         tmp = reallocarray(comm_strs->strs,
 153                                            comm_strs->capacity + 16,
 154                                            sizeof(*comm_strs->strs));
 155                         if (!tmp) {
 156                                 up_write(&comm_strs->lock);
 157                                 return NULL;
 158                         }
 159                         comm_strs->strs = tmp;
 160                         comm_strs->capacity += 16;
 161                 }
 162                 result = comm_str__new(str);
 163                 if (result) {
 164                         int low = 0, high = comm_strs->num_strs - 1;
 165                         int insert = comm_strs->num_strs; /* Default to inserting at the end. */
 166
 167                         while (low <= high) {
 168                                 int mid = low + (high - low) / 2;
 169                                 int cmp = strcmp(comm_str__str(comm_strs->strs[mid]), str);
 170
 171                                 if (cmp < 0) {
 172                                         low = mid + 1;
 173                                 } else {
 174                                         high = mid - 1;
 175                                         insert = mid;
 176                                 }
 177                         }
 178                         memmove(&comm_strs->strs[insert + 1], &comm_strs->strs[insert],
 179                                 (comm_strs->num_strs - insert) * sizeof(struct comm_str *));
 180                         comm_strs->num_strs++;
 181                         comm_strs->strs[insert] = result;
 182                 }
 183         }
 184         up_write(&comm_strs->lock);
 185         return comm_str__get(result);
 186 }
 187
 188 struct comm *comm__new(const char *str, u64 timestamp, bool exec)
 189 {
 190         struct comm *comm = zalloc(sizeof(*comm));
 191
 192         if (!comm)
 193                 return NULL;
 194
 195         comm->start = timestamp;
 196         comm->exec = exec;
 197
 198         comm->comm_str = comm_strs__findnew(str);
 199         if (!comm->comm_str) {
 200                 free(comm);
 201                 return NULL;
 202         }
 203
 204         return comm;
 205 }
 206
 207 int comm__override(struct comm *comm, const char *str, u64 timestamp, bool exec)
 208 {
 209         struct comm_str *new, *old = comm->comm_str;
 210
 211         new = comm_strs__findnew(str);
 212         if (!new)
 213                 return -ENOMEM;
 214
 215         comm_str__put(old);
 216         comm->comm_str = new;
 217         comm->start = timestamp;
 218         if (exec)
 219                 comm->exec = true;
 220
 221         return 0;
 222 }
 223
 224 void comm__free(struct comm *comm)
 225 {
 226         comm_str__put(comm->comm_str);
 227         free(comm);
 228 }
 229
 230 const char *comm__str(const struct comm *comm)
 231 {
 232         return comm_str__str(comm->comm_str);
 233 }