libgo/runtime/thread.c

   1 // Copyright 2010 The Go Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style
   3 // license that can be found in the LICENSE file.
   4
   5 #include <errno.h>
   6 #include "runtime.h"
   7 #include "go-assert.h"
   8
   9 void
  10 runtime_initlock(Lock *l)
  11 {
  12         l->key = 0;
  13         if(sem_init(&l->sem, 0, 0) != 0)
  14                 runtime_throw("sem_init failed");
  15 }
  16
  17 // noinline so that runtime_lock doesn't have to split the stack.
  18 static void runtime_lock_full(Lock *l) __attribute__ ((noinline));
  19
  20 static void
  21 runtime_lock_full(Lock *l)
  22 {
  23         for(;;){
  24                 if(sem_wait(&l->sem) == 0)
  25                         return;
  26                 if(errno != EINTR)
  27                         runtime_throw("sem_wait failed");
  28         }
  29 }
  30
  31 void
  32 runtime_lock(Lock *l)
  33 {
  34         if(m != nil) {
  35                 if(m->locks < 0)
  36                         runtime_throw("lock count");
  37                 m->locks++;
  38         }
  39
  40         if(runtime_xadd(&l->key, 1) > 1)        // someone else has it; wait
  41                 runtime_lock_full(l);
  42 }
  43
  44 static void runtime_unlock_full(Lock *l) __attribute__ ((noinline));
  45
  46 static void
  47 runtime_unlock_full(Lock *l)
  48 {
  49         if(sem_post(&l->sem) != 0)
  50                 runtime_throw("sem_post failed");
  51 }
  52
  53 void
  54 runtime_unlock(Lock *l)
  55 {
  56         if(m != nil) {
  57                 m->locks--;
  58                 if(m->locks < 0)
  59                         runtime_throw("lock count");
  60         }
  61
  62         if(runtime_xadd(&l->key, -1) > 0)       // someone else is waiting
  63                 runtime_unlock_full(l);
  64 }
  65
  66 void
  67 runtime_destroylock(Lock *l)
  68 {
  69         sem_destroy(&l->sem);
  70 }
  71
  72 #ifndef HAVE_SYNC_BOOL_COMPARE_AND_SWAP_4
  73
  74 // For targets which don't have the required sync support.  Really
  75 // this should be provided by gcc itself.  FIXME.
  76
  77 static pthread_mutex_t sync_lock = PTHREAD_MUTEX_INITIALIZER;
  78
  79 _Bool
  80 __sync_bool_compare_and_swap_4(uint32*, uint32, uint32)
  81   __attribute__((visibility("hidden")));
  82
  83 _Bool
  84 __sync_bool_compare_and_swap_4(uint32* ptr, uint32 old, uint32 new)
  85 {
  86   int i;
  87   _Bool ret;
  88
  89   i = pthread_mutex_lock(&sync_lock);
  90   __go_assert(i == 0);
  91
  92   if(*ptr != old) {
  93     ret = 0;
  94   } else {
  95     *ptr = new;
  96     ret = 1;
  97   }
  98
  99   i = pthread_mutex_unlock(&sync_lock);
 100   __go_assert(i == 0);
 101
 102   return ret;
 103 }
 104
 105 #endif