path: root/libjava/posix-threads.cc

// posix-threads.cc - interface between libjava and POSIX threads.

/* Copyright (C) 1998, 1999  Cygnus Solutions

   This file is part of libgcj.

This software is copyrighted work licensed under the terms of the
Libgcj License.  Please consult the file "LIBGCJ_LICENSE" for
details.  */

// TO DO:
// * Document signal handling limitations

#include <config.h>

// If we're using the Boehm GC, then we need to override some of the
// thread primitives.  This is fairly gross.
#ifdef HAVE_BOEHM_GC
extern "C"
{
#include <boehm-config.h>
#include <gc.h>
};
#endif /* HAVE_BOEHM_GC */

#include <stdlib.h>
#include <time.h>
#include <signal.h>

#include <cni.h>
#include <jvm.h>
#include <java/lang/Thread.h>
#include <java/lang/System.h>

// This is used to implement thread startup.
struct starter
{
  _Jv_ThreadStartFunc *method;
  java::lang::Thread *object;
  _Jv_Thread_t *data;
};

// This is the key used to map from the POSIX thread value back to the
// Java object representing the thread.  The key is global to all
// threads, so it is ok to make it a global here.
pthread_key_t _Jv_ThreadKey;

// We keep a count of all non-daemon threads which are running.  When
// this reaches zero, _Jv_ThreadWait returns.
static pthread_mutex_t daemon_mutex;
static pthread_cond_t daemon_cond;
static int non_daemon_count;

// The signal to use when interrupting a thread.
#ifdef LINUX_THREADS
  // LinuxThreads usurps both SIGUSR1 and SIGUSR2.
#  define INTR SIGHUP
#else /* LINUX_THREADS */
#  define INTR SIGUSR2
#endif /* LINUX_THREADS */

//
// These are the flags that can appear in _Jv_Thread_t.
//

// Thread started.
#define FLAG_START   0x01
// Thread is daemon.
#define FLAG_DAEMON  0x02



int
_Jv_CondWait (_Jv_ConditionVariable_t *cv, _Jv_Mutex_t *mu,
	      jlong millis, jint nanos)
{
  int r;
  pthread_mutex_t *pmu;
#ifdef HAVE_RECURSIVE_MUTEX
  pmu = mu;
#else
  pmu = &mu->mutex2;
#endif
  if (millis == 0 && nanos == 0)
    r = pthread_cond_wait (cv, pmu);
  else
    {
      struct timespec ts; 
      jlong m = millis + java::lang::System::currentTimeMillis (); 
      ts.tv_sec = m / 1000; 
      ts.tv_nsec = ((m % 1000) * 1000000) + nanos; 
             
      r = pthread_cond_timedwait (cv, pmu, &ts);
    }
  return r;
}

#ifndef RECURSIVE_MUTEX_IS_DEFAULT

void
_Jv_MutexInit (_Jv_Mutex_t *mu)
{
#ifdef HAVE_RECURSIVE_MUTEX
  pthread_mutexattr_t *val = NULL;

#if defined (HAVE_PTHREAD_MUTEXATTR_SETTYPE)
  pthread_mutexattr_t attr;

  // If this is slow, then allocate it statically and only initialize
  // it once.
  pthread_mutexattr_init (&attr);
  pthread_mutexattr_settype (&attr, PTHREAD_MUTEX_RECURSIVE);
  val = &attr;
#elif defined (HAVE_PTHREAD_MUTEXATTR_SETKIND_NP)
  pthread_mutexattr_t attr;
  pthread_mutexattr_init (&attr);
  pthread_mutexattr_setkind_np (&attr, PTHREAD_MUTEX_RECURSIVE_NP);
  val = &attr;
#endif

  pthread_mutex_init (mu, val);

#if defined (HAVE_PTHREAD_MUTEXATTR_SETTYPE) || defined (HAVE_PTHREAD_MUTEXATTR_SETKIND_NP)
  pthread_mutexattr_destroy (&attr);
#endif

#else /* HAVE_RECURSIVE_MUTEX */

  // No recursive mutex, so simulate one.
  pthread_mutex_init (&mu->mutex, NULL);
  pthread_mutex_init (&mu->mutex2, NULL);
  pthread_cond_init (&mu->cond, 0);
  mu->count = 0;

#endif /* HAVE_RECURSIVE_MUTEX */
}

#endif /* not RECURSIVE_MUTEX_IS_DEFAULT */

#if ! defined (LINUX_THREADS) && ! defined (HAVE_RECURSIVE_MUTEX)

void
_Jv_MutexDestroy (_Jv_Mutex_t *mu)
{
  pthread_mutex_destroy (&mu->mutex);
  pthread_mutex_destroy (&mu->mutex2);
  pthread_cond_destroy (&mu->cond);
}

int
_Jv_MutexLock (_Jv_Mutex_t *mu)
{
  if (pthread_mutex_lock (&mu->mutex))
    return -1;
  while (1)
    {
      if (mu->count == 0)
	{
	  // Grab the lock.
	  mu->thread = pthread_self ();
	  mu->count = 1;
	  pthread_mutex_lock (&mu->mutex2);
	  break;
	}
      else if (pthread_self () == mu->thread)
	{
	  // Already have the lock.
	  mu->count += 1;
	  break;
	}
      else
	{
	  // Try to acquire the lock.
	  pthread_cond_wait (&mu->cond, &mu->mutex);
	}
    }
  pthread_mutex_unlock (&mu->mutex);
  return 0;
}

int
_Jv_MutexUnlock (_Jv_Mutex_t *mu)
{
  if (pthread_mutex_lock (&mu->mutex))
    return -1;
  int r = 0;
  if (mu->count == 0 || pthread_self () != mu->thread)
    r = -1;
  else
    {
      mu->count -= 1;
      if (! mu->count)
	{
	  pthread_mutex_unlock (&mu->mutex2);
	  pthread_cond_signal (&mu->cond);
	}
    }
  pthread_mutex_unlock (&mu->mutex);
  return r;
}

#endif /* not LINUX_THREADS and not HAVE_RECURSIVE_MUTEX */

static void
handle_intr (int)
{
  // Do nothing.
}

void
_Jv_InitThreads (void)
{
  pthread_key_create (&_Jv_ThreadKey, NULL);
  pthread_mutex_init (&daemon_mutex, NULL);
  pthread_cond_init (&daemon_cond, 0);
  non_daemon_count = 0;

  // Arrange for the interrupt signal to interrupt system calls.
  struct sigaction act;
  act.sa_handler = handle_intr;
  sigemptyset (&act.sa_mask);
  act.sa_flags = 0;
  sigaction (INTR, &act, NULL);

  // Arrange for SIGINT to be blocked to all threads.  It is only
  // deliverable to the master thread.
  sigset_t mask;
  sigemptyset (&mask);
  sigaddset (&mask, SIGINT);
  pthread_sigmask (SIG_BLOCK, &mask, NULL);
}

void
_Jv_ThreadInitData (_Jv_Thread_t **data, java::lang::Thread *)
{
  _Jv_Thread_t *info = new _Jv_Thread_t;

  info->flags = 0;
  info->exception = NULL;

  // FIXME register a finalizer for INFO here.
  // FIXME also must mark INFO somehow.

  *data = info;
}

void
_Jv_ThreadSetPriority (_Jv_Thread_t *data, jint prio)
{
  if (data->flags & FLAG_START)
    {
      struct sched_param param;

      param.sched_priority = prio;
      pthread_setschedparam (data->thread, SCHED_RR, &param);
    }
}


// This is called as a cleanup handler when a thread is exiting.  We
// use it to throw the requested exception.  It's entirely possible
// that this approach is doomed to failure, in which case we'll need
// to adopt some alternate.  For instance, use a signal to implement
// _Jv_ThreadCancel.
static void
throw_cleanup (void *data)
{
  _Jv_Thread_t *td = (_Jv_Thread_t *) data;
  _Jv_Throw ((java::lang::Throwable *) td->exception);
}

void
_Jv_ThreadCancel (_Jv_Thread_t *data, void *error)
{
  data->exception = error;
  pthread_cancel (data->thread);
}

// This function is called when a thread is started.  We don't arrange
// to call the `run' method directly, because this function must
// return a value.
static void *
really_start (void *x)
{
  struct starter *info = (struct starter *) x;

  pthread_cleanup_push (throw_cleanup, info->data);
  pthread_setspecific (_Jv_ThreadKey, info->object);
  info->method (info->object);
  pthread_cleanup_pop (0);

  if (! (info->data->flags & FLAG_DAEMON))
    {
      pthread_mutex_lock (&daemon_mutex);
      --non_daemon_count;
      if (! non_daemon_count)
	pthread_cond_signal (&daemon_cond);
      pthread_mutex_unlock (&daemon_mutex);
    }

  return NULL;
}

void
_Jv_ThreadStart (java::lang::Thread *thread, _Jv_Thread_t *data,
		 _Jv_ThreadStartFunc *meth)
{
  struct sched_param param;
  pthread_attr_t attr;
  struct starter *info;

  if (data->flags & FLAG_START)
    return;
  data->flags |= FLAG_START;

  param.sched_priority = thread->getPriority();

  pthread_attr_init (&attr);
  pthread_attr_setschedparam (&attr, &param);

  // FIXME: handle marking the info object for GC.
  info = (struct starter *) _Jv_AllocBytes (sizeof (struct starter));
  info->method = meth;
  info->object = thread;
  info->data = data;

  if (! thread->isDaemon())
    {
      pthread_mutex_lock (&daemon_mutex);
      ++non_daemon_count;
      pthread_mutex_unlock (&daemon_mutex);
    }
  else
    data->flags |= FLAG_DAEMON;
  pthread_create (&data->thread, &attr, really_start, (void *) info);

  pthread_attr_destroy (&attr);
}

void
_Jv_ThreadWait (void)
{
  // Arrange for SIGINT to be delivered to the master thread.
  sigset_t mask;
  sigemptyset (&mask);
  sigaddset (&mask, SIGINT);
  pthread_sigmask (SIG_UNBLOCK, &mask, NULL);

  pthread_mutex_lock (&daemon_mutex);
  if (non_daemon_count)
    pthread_cond_wait (&daemon_cond, &daemon_mutex);
  pthread_mutex_unlock (&daemon_mutex);
}

void
_Jv_ThreadInterrupt (_Jv_Thread_t *data)
{
  pthread_kill (data->thread, INTR);
}