nsz Git - musl/blob - src/thread/pthread_key_create.c

   1 #include "pthread_impl.h"
   2
   3 volatile size_t __pthread_tsd_size = sizeof(void *) * PTHREAD_KEYS_MAX;
   4 void *__pthread_tsd_main[PTHREAD_KEYS_MAX] = { 0 };
   5
   6 static void (*keys[PTHREAD_KEYS_MAX])(void *);
   7
   8 static pthread_rwlock_t key_lock = PTHREAD_RWLOCK_INITIALIZER;
   9
  10 static pthread_key_t next_key;
  11
  12 static void nodtor(void *dummy)
  13 {
  14 }
  15
  16 static void dirty(void *dummy)
  17 {
  18 }
  19
  20 struct cleanup_args {
  21         pthread_t caller;
  22         int ret;
  23 };
  24
  25 static void clean_dirty_tsd_callback(void *p)
  26 {
  27         struct cleanup_args *args = p;
  28         pthread_t self = __pthread_self();
  29         pthread_key_t i;
  30         for (i=0; i<PTHREAD_KEYS_MAX; i++) {
  31                 if (keys[i] == dirty && self->tsd[i])
  32                         self->tsd[i] = 0;
  33         }
  34         /* Arbitrary choice to avoid data race. */
  35         if (args->caller == self) args->ret = 0;
  36 }
  37
  38 static int clean_dirty_tsd(void)
  39 {
  40         struct cleanup_args args = {
  41                 .caller = __pthread_self(),
  42                 .ret = EAGAIN
  43         };
  44         __pthread_key_delete_synccall(clean_dirty_tsd_callback, &args);
  45         return args.ret;
  46 }
  47
  48 int __pthread_key_create(pthread_key_t *k, void (*dtor)(void *))
  49 {
  50         pthread_key_t j = next_key;
  51         pthread_t self = __pthread_self();
  52         int found_dirty = 0;
  53
  54         /* This can only happen in the main thread before
  55          * pthread_create has been called. */
  56         if (!self->tsd) self->tsd = __pthread_tsd_main;
  57
  58         /* Purely a sentinel value since null means slot is free. */
  59         if (!dtor) dtor = nodtor;
  60
  61         pthread_rwlock_wrlock(&key_lock);
  62         do {
  63                 if (!keys[j]) {
  64                         keys[next_key = *k = j] = dtor;
  65                         pthread_rwlock_unlock(&key_lock);
  66                         return 0;
  67                 } else if (keys[j] == dirty) {
  68                         found_dirty = 1;
  69                 }
  70         } while ((j=(j+1)%PTHREAD_KEYS_MAX) != next_key);
  71
  72         /* It's possible that all slots are in use or __synccall fails. */
  73         if (!found_dirty || clean_dirty_tsd()) {
  74                 pthread_rwlock_unlock(&key_lock);
  75                 return EAGAIN;
  76         }
  77
  78         /* If this point is reached there is necessarily a newly-cleaned
  79          * slot to allocate to satisfy the caller's request. Find it and
  80          * mark any additional previously-dirty slots clean. */
  81         for (j=0; j<PTHREAD_KEYS_MAX; j++) {
  82                 if (keys[j] == dirty) {
  83                         if (dtor) {
  84                                 keys[next_key = *k = j] = dtor;
  85                                 dtor = 0;
  86                         } else {
  87                                 keys[j] = 0;
  88                         }
  89                 }
  90         }
  91
  92         pthread_rwlock_unlock(&key_lock);
  93         return 0;
  94 }
  95
  96 int __pthread_key_delete_impl(pthread_key_t k)
  97 {
  98         pthread_rwlock_wrlock(&key_lock);
  99         keys[k] = dirty;
 100         pthread_rwlock_unlock(&key_lock);
 101         return 0;
 102 }
 103
 104 void __pthread_tsd_run_dtors()
 105 {
 106         pthread_t self = __pthread_self();
 107         int i, j;
 108         for (j=0; self->tsd_used && j<PTHREAD_DESTRUCTOR_ITERATIONS; j++) {
 109                 pthread_rwlock_rdlock(&key_lock);
 110                 self->tsd_used = 0;
 111                 for (i=0; i<PTHREAD_KEYS_MAX; i++) {
 112                         void *val = self->tsd[i];
 113                         void (*dtor)(void *) = keys[i];
 114                         self->tsd[i] = 0;
 115                         if (val && dtor && dtor != nodtor && dtor != dirty) {
 116                                 pthread_rwlock_unlock(&key_lock);
 117                                 dtor(val);
 118                                 pthread_rwlock_rdlock(&key_lock);
 119                         }
 120                 }
 121                 pthread_rwlock_unlock(&key_lock);
 122         }
 123 }
 124
 125 weak_alias(__pthread_key_create, pthread_key_create);