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 "runtime.h"
   6
   7 void
   8 runtime_initlock(Lock *l)
   9 {
  10         l->key = 0;
  11         if(sem_init(&l->sem, 0, 0) != 0)
  12                 runtime_throw("sem_init failed");
  13 }
  14
  15 static uint32
  16 runtime_xadd(uint32 volatile *val, int32 delta)
  17 {
  18         uint32 oval, nval;
  19
  20         for(;;){
  21                 oval = *val;
  22                 nval = oval + delta;
  23                 if(runtime_cas(val, oval, nval))
  24                         return nval;
  25         }
  26 }
  27
  28 // noinline so that runtime_lock doesn't have to split the stack.
  29 static void runtime_lock_full(Lock *l) __attribute__ ((noinline));
  30
  31 static void
  32 runtime_lock_full(Lock *l)
  33 {
  34         if(sem_wait(&l->sem) != 0)
  35                 runtime_throw("sem_wait failed");
  36 }
  37
  38 void
  39 runtime_lock(Lock *l)
  40 {
  41         if(m->locks < 0)
  42                 runtime_throw("lock count");
  43         m->locks++;
  44
  45         if(runtime_xadd(&l->key, 1) > 1)        // someone else has it; wait
  46                 runtime_lock_full(l);
  47 }
  48
  49 static void runtime_unlock_full(Lock *l) __attribute__ ((noinline));
  50
  51 static void
  52 runtime_unlock_full(Lock *l)
  53 {
  54         if(sem_post(&l->sem) != 0)
  55                 runtime_throw("sem_post failed");
  56 }
  57
  58 void
  59 runtime_unlock(Lock *l)
  60 {
  61         m->locks--;
  62         if(m->locks < 0)
  63                 runtime_throw("lock count");
  64
  65         if(runtime_xadd(&l->key, -1) > 0)       // someone else is waiting
  66                 runtime_unlock_full(l);
  67 }
  68
  69 void
  70 runtime_destroylock(Lock *l)
  71 {
  72         sem_destroy(&l->sem);
  73 }