libs-base/Source/NSThread.m

/** Control of executable units within a shared virtual memory space
   Copyright (C) 1996-2018 Free Software Foundation, Inc.

   Original Author:  Scott Christley <scottc@net-community.com>
   Rewritten by: Andrew Kachites McCallum <mccallum@gnu.ai.mit.edu>
   Created: 1996
   Rewritten by: Richard Frith-Macdonald <richard@brainstorm.co.uk>
   to add optimisations features for faster thread access.
   Modified by: Nicola Pero <n.pero@mi.flashnet.it>
   to add GNUstep extensions allowing to interact with threads created
   by external libraries/code (eg, a Java Virtual Machine).

   This file is part of the GNUstep Objective-C Library.

   This library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Lesser General Public
   License as published by the Free Software Foundation; either
   version 2 of the License, or (at your option) any later version.

   This library is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public
   License along with this library; if not, write to the Free
   Software Foundation, Inc., 31 Milk Street #960789 Boston, MA 02196 USA.

   <title>NSThread class reference</title>
*/

#import "common.h"

#import "GSPThread.h"

#ifdef _WIN32
#import <processthreadsapi.h>
#endif

// Dummy implementatation
// cleaner than IFDEF'ing the code everywhere
#ifndef HAVE_PTHREAD_SPIN_LOCK
typedef volatile int pthread_spinlock_t;
int pthread_spin_init(pthread_spinlock_t *lock, int pshared)
{
#if DEBUG && !__has_builtin(__sync_bool_compare_and_swap)
  fprintf(stderr,"NSThread.m: Warning this platform does not support spin locks - init.\n");
#endif
  return 0;
}
int pthread_spin_lock(pthread_spinlock_t *lock)
{
#if __has_builtin(__sync_bool_compare_and_swap)
  int count = 0;
  // Set the spin lock value to 1 if it is 0.
  while(!__sync_bool_compare_and_swap(lock, 0, 1))
  {
    count++;
    if (0 == count % 10)
    {
      // If it is already 1, let another thread play with the CPU for a
      // bit then try again.
#if defined(_WIN32)
      Sleep(0);
#else
      sleep(0);
#endif
    }
  }
#else
  #warning no spin_locks, using dummy versions
#endif
  return 0;
}
int pthread_spin_unlock(pthread_spinlock_t *lock)
{
#if __has_builtin(__sync_bool_compare_and_swap)
  __sync_synchronize();
  *lock = 0;
#endif
  return 0;
}
int pthread_spin_destroy(pthread_spinlock_t *lock)
{
  return 0;
}
#endif /* HAVE_PTHREAD_SPIN_LOCK */

/** Structure for holding lock information for a thread.
 */
typedef struct {
  pthread_spinlock_t    spin;   /* protect access to struct members */
  NSHashTable           *held;  /* all locks/conditions held by thread */
  id                    wait;   /* the lock/condition we are waiting for */
} GSLockInfo;

#define	EXPOSE_NSThread_IVARS	1
#define	GS_NSThread_IVARS \
  id                    _stringCollatorCache; \
  BOOL                  _targetIsBlock; \
  gs_thread_id_t        _pthreadID; \
  NSUInteger            _threadID; \
  GSLockInfo            _lockInfo


#ifdef HAVE_NANOSLEEP
#  include <time.h>
#endif
#ifdef HAVE_SYS_TIME_H
#  include <sys/time.h>
#endif
#ifdef HAVE_SYS_RESOURCE_H
#  include <sys/resource.h>
#endif

#if	defined(HAVE_SYS_FILE_H)
#  include <sys/file.h>
#endif

#if defined(__ANDROID__)
#  include <string.h>       // For strerror
#  include <sys/resource.h> // For getpriority and setpriority
#endif

#if	defined(HAVE_SYS_FCNTL_H)
#  include <sys/fcntl.h>
#elif	defined(HAVE_FCNTL_H)
#  include <fcntl.h>
#endif

#if defined(__POSIX_SOURCE)\
        || defined(__EXT_POSIX1_198808)\
        || defined(O_NONBLOCK)
#define NBLK_OPT     O_NONBLOCK
#else
#define NBLK_OPT     FNDELAY
#endif

#import "Foundation/NSException.h"
#import "Foundation/NSHashTable.h"
#import "Foundation/NSThread.h"
#import "Foundation/NSLock.h"
#import "Foundation/NSMapTable.h"
#import "Foundation/NSNotification.h"
#import "Foundation/NSNotificationQueue.h"
#import "Foundation/NSRunLoop.h"
#import "Foundation/NSConnection.h"
#import "Foundation/NSInvocation.h"
#import "Foundation/NSUserDefaults.h"
#import "Foundation/NSValue.h"

#import "GSPrivate.h"
#import "GSRunLoopCtxt.h"

#if defined(HAVE_PTHREAD_NP_H)
#  include <pthread_np.h>
#endif

#if defined(HAVE_GETTID)
#  include <unistd.h>
#  include <sys/syscall.h>
#  include <sys/types.h>
#endif

#define GSInternal      NSThreadInternal
#include        "GSInternal.h"
GS_PRIVATE_INTERNAL(NSThread)

#define pthreadID (internal->_pthreadID)
#define threadID (internal->_threadID)
#define lockInfo (internal->_lockInfo)
#define targetIsBlock (internal->_targetIsBlock)
#define stringCollatorCache (internal->_stringCollatorCache)


#if defined(HAVE_PTHREAD_MAIN_NP)
#  define IS_MAIN_PTHREAD (pthread_main_np() == 1)
#elif defined(HAVE_GETTID)
#  define IS_MAIN_PTHREAD (getpid() == (pid_t)syscall(SYS_gettid))
#else
#  define IS_MAIN_PTHREAD (1)
#endif

/* Return the current thread ID as an unsigned long.
 * Ideally, we use the operating-system's notion of a thread ID so
 * that external process monitoring software will be using the same
 * value that we log.  If we don't know the system's mechanism, we
 * use the address of the current NSThread object so that, even if
 * it makes no sense externally, it can still be used to show that
 * different threads generated different logs.
 */
NSUInteger
GSPrivateThreadID()
{
#if defined(_WIN32)
  return (NSUInteger)GetCurrentThreadId();
#elif defined(HAVE_GETTID)
  return (NSUInteger)syscall(SYS_gettid);
#elif defined(HAVE_PTHREAD_GETTHREADID_NP)
  return (NSUInteger)pthread_getthreadid_np();
#else
  return (NSUInteger)GSCurrentThread();
#endif
}

#ifndef PTHREAD_SETNAME
#define PTHREAD_SETNAME(a) -1
#endif

#ifndef PTHREAD_GETNAME
#define PTHREAD_GETNAME(a, b) -1
#endif


@interface NSThread (Activation)
- (void) _makeThreadCurrent;
@end

@interface NSAutoreleasePool (NSThread)
+ (void) _endThread: (NSThread*)thread;
@end

static Class                    threadClass = Nil;
static NSNotificationCenter     *nc = nil;
static BOOL                     disableTraceLocks = NO;

/**
 * This class performs a dual function ...
 * <p>
 *   As a class, it is responsible for handling incoming events from
 *   the main runloop on a special inputFd.  This consumes any bytes
 *   written to wake the main runloop.<br />
 *   During initialisation, the default runloop is set up to watch
 *   for data arriving on inputFd.
 * </p>
 * <p>
 *   As instances, each  instance retains perform receiver and argument
 *   values as long as they are needed, and handles locking to support
 *   methods which want to block until an action has been performed.
 * </p>
 * <p>
 *   The initialize method of this class is called before any new threads
 *   run.
 * </p>
 */
@interface GSPerformHolder : NSObject
{
  id			receiver;
  id			argument;
  SEL			selector;
  NSConditionLock	*lock;		// Not retained.
  NSArray		*modes;
  BOOL                  invalidated;
@public
  NSException           *exception;
}
+ (GSPerformHolder*) newForReceiver: (id)r
			   argument: (id)a
			   selector: (SEL)s
			      modes: (NSArray*)m
			       lock: (NSConditionLock*)l;
- (void) fire;
- (void) invalidate;
- (BOOL) isInvalidated;
- (NSArray*) modes;
@end

/**
 * Sleep until the current date/time is the specified time interval
 * past the reference date/time.<br />
 * Implemented as a function taking an NSTimeInterval argument in order
 * to avoid objc messaging and object allocation/deallocation (NSDate)
 * overheads.<br />
 * Used to implement [NSThread+sleepUntilDate:]
 * If the date is in the past, this function simply allows other threads
 * (if any) to run.
 */
void
GSSleepUntilIntervalSinceReferenceDate(NSTimeInterval when)
{
  NSTimeInterval delay;

  // delay is always the number of seconds we still need to wait
  delay = when - GSPrivateTimeNow();
  if (delay <= 0.0)
    {
      /* We don't need to wait, but since we are willing to wait at this
       * point, we should let other threads have preference over this one.
       */
      GS_YIELD();
      return;
    }

#if     defined(_WIN32)
  /*
   * Avoid integer overflow by breaking up long sleeps.
   */
  while (delay > 30.0*60.0)
    {
      // sleep 30 minutes
      Sleep (30*60*1000);
      delay = when - GSPrivateTimeNow();
    }

  /* Don't use nanosleep (even if available) on mingw ... it's reported no
   * to work with pthreads.
   * Sleeping may return early because of signals, so we need to re-calculate
   * the required delay and check to see if we need to sleep again.
   */
  while (delay > 0)
    {
#if	defined(HAVE_USLEEP)
      /* On windows usleep() seems to perform a busy wait ... so we only
       * use it for short delays ... otherwise use the less accurate Sleep()
       */
      if (delay > 0.1)
	{
          Sleep ((NSInteger)(delay*1000));
	}
      else
	{
          usleep ((NSInteger)(delay*1000000));
	}
#else
      Sleep ((NSInteger)(delay*1000));
#endif	/* HAVE_USLEEP */
      delay = when - GSPrivateTimeNow();
    }

#else   /* _WIN32 */

  /*
   * Avoid integer overflow by breaking up long sleeps.
   */
  while (delay > 30.0*60.0)
    {
      // sleep 30 minutes
      sleep(30*60);
      delay = when - GSPrivateTimeNow();
    }

#ifdef	HAVE_NANOSLEEP
  if (delay > 0)
    {
      struct timespec request;
      struct timespec remainder;

      request.tv_sec = (time_t)delay;
      request.tv_nsec = (long)((delay - request.tv_sec) * 1000000000);
      remainder.tv_sec = 0;
      remainder.tv_nsec = 0;

      /*
       * With nanosleep, we can restart the sleep after a signal by using
       * the remainder information ... so we can be sure to sleep to the
       * desired limit without having to re-generate the delay needed.
       */
      while (nanosleep(&request, &remainder) < 0
	&& (remainder.tv_sec > 0 || remainder.tv_nsec > 0))
	{
	  request.tv_sec = remainder.tv_sec;
	  request.tv_nsec = remainder.tv_nsec;
	  remainder.tv_sec = 0;
	  remainder.tv_nsec = 0;
	}
    }
#else   /* HAVE_NANOSLEEP */

  /*
   * sleeping may return early because of signals, so we need to re-calculate
   * the required delay and check to see if we need to sleep again.
   */
  while (delay > 0)
    {
#if	defined(HAVE_USLEEP)
      usleep((NSInteger)(delay*1000000));
#else	/* HAVE_USLEEP */
      sleep((NSInteger)delay);
#endif	/* !HAVE_USLEEP */
      delay = when - GSPrivateTimeNow();
    }
#endif	/* !HAVE_NANOSLEEP */
#endif	/* !_WIN32 */
}

static NSArray *
commonModes(void)
{
  static gs_mutex_t     modesLock = GS_MUTEX_INIT_STATIC;
  static NSArray	*modes = nil;

  if (modes == nil)
    {
      GS_MUTEX_LOCK(modesLock);
      if (modes == nil)
	{
	  Class	c = NSClassFromString(@"NSApplication");
	  SEL	s = @selector(allRunLoopModes);

	  if (c != 0 && [c respondsToSelector: s])
	    {
	      modes = RETAIN([c performSelector: s]);
	    }
	  else
	    {
	      modes = [[NSArray alloc] initWithObjects:
		NSDefaultRunLoopMode, NSConnectionReplyMode, nil];
	    }
	}
      GS_MUTEX_UNLOCK(modesLock);
    }
  return modes;
}

/*
 * Flag indicating whether the objc runtime ever went multi-threaded.
 */
static BOOL	entered_multi_threaded_state = NO;

static NSThread *defaultThread;

static BOOL             keyInitialized = NO;
static gs_thread_key_t  thread_object_key;


static NSHashTable *_activeBlocked = nil;
static NSHashTable *_activeThreads = nil;
static gs_mutex_t _activeLock = GS_MUTEX_INIT_STATIC;

/**
 * pthread_t is an opaque type. It might be a scalar type or
 * some kind of struct depending on the implementation, so we
 * need to wrap it up in an NSValue object if we want to pass
 * it around.
 * This follows the CoreFoundation 'create rule' and returns an object with
 * a reference count of 1.
 */
static inline NSValue* NSValueCreateFromPthread(gs_thread_id_t thread)
{
  return [[NSValue alloc] initWithBytes: &thread
                               objCType: @encode(gs_thread_id_t)];
}

/**
 * Conversely, we need to be able to retrieve the pthread_t
 * from an NSValue.
 */
static inline void
_getPthreadFromNSValue(const void *value, gs_thread_id_t *thread_ptr)
{
  const char    *enc;

  NSCAssert(thread_ptr, @"No storage for thread reference");
# ifndef NS_BLOCK_ASSERTIONS
  enc = [(NSValue*)value objCType];
  NSCAssert(enc != NULL && (0 == strcmp(@encode(gs_thread_id_t),enc)),
    @"Invalid NSValue container for thread reference");
# endif
  [(NSValue*)value getValue: (void*)thread_ptr];
}

/**
 * This is the comparison function for boxed pthreads, as used by the
 * NSMapTable containing them.
 */
static BOOL
_boxedPthreadIsEqual(NSMapTable *t,
  const void *boxed,
  const void *boxedOther)
{
  gs_thread_id_t thread;
  gs_thread_id_t otherThread;

  _getPthreadFromNSValue(boxed, &thread);
  _getPthreadFromNSValue(boxedOther, &otherThread);

#if GS_USE_WIN32_THREADS_AND_LOCKS
  return thread == otherThread;
#else
  return pthread_equal(thread, otherThread);
#endif
}

/**
 * Since pthread_t is opaque, we cannot make any assumption about how
 * to hash it. There are a few problems here:
 * 1. Functions to obtain the thread ID of an arbitrary thread
 *    exist in the in the Win32 and some pthread APIs (GetThreadId() and
 *    pthread_getunique_np(), respectively), but there is no protable solution
 *    for this problem.
 * 2. Even where pthread_getunique_np() is available, it might have different
 *    definitions, so it's not really robust to use it.
 *
 * For these reasons, we always return the same hash. That fulfills the API
 * contract for NSMapTable (key-hash equality as a necessary condition for key
 * equality), but makes things quite inefficient (linear search over all
 * elements), so we need to keep the table small.
 */
static NSUInteger _boxedPthreadHash(NSMapTable *t, const void *value)
{
  return 0;
}

/**
 * Retain callback for boxed thread references.
 */
static void _boxedPthreadRetain(NSMapTable *t, const void *value)
{
  RETAIN((NSValue*)value);
}

/**
 * Release callback for boxed thread references.
 */
static void _boxedPthreadRelease(NSMapTable *t, void *value)
{
  RELEASE((NSValue*)value);
}

/**
 * Description callback for boxed thread references.
 */
static NSString *_boxedPthreadDescribe(NSMapTable *t, const void *value)
{
  return [(NSValue*)value description];
}


static const NSMapTableKeyCallBacks _boxedPthreadKeyCallBacks =
{
  _boxedPthreadHash,
  _boxedPthreadIsEqual,
  _boxedPthreadRetain,
  _boxedPthreadRelease,
  _boxedPthreadDescribe,
  NULL
};


/**
 * This map table maintains a list of all threads currently undergoing
 * cleanup. This is a required so that +currentThread can still find the
 * thred if called from within the late-cleanup function.
 */
static NSMapTable *_exitingThreads = nil;
static gs_mutex_t _exitingThreadsLock = GS_MUTEX_INIT_STATIC;


/**
 * Called before late cleanup is run and inserts the NSThread object into the
 * table that is used by GSCurrentThread to find the thread if it is called
 * during cleanup. The boxedThread variable contains a boxed reference to
 * the result of calling pthread_self().
 */
static inline void _willLateUnregisterThread(NSValue *boxedThread,
  NSThread *specific)
{
  GS_MUTEX_LOCK(_exitingThreadsLock);
  /* The map table is created lazily/late so that the NSThread
   * +initialize method can be called without causing other
   * classes to be initialized.
   * NB this locked section cannot be protected by an exception handler
   * because the exception handler stores information in the current
   * thread variables ... which causes recursion.
   */
  if (nil == _exitingThreads)
    {
      _exitingThreads = NSCreateMapTable(_boxedPthreadKeyCallBacks,
	NSObjectMapValueCallBacks, 10);
    }
  NSMapInsert(_exitingThreads, (const void*)boxedThread,
    (const void*)specific);
  GS_MUTEX_UNLOCK(_exitingThreadsLock);
}

/**
 * Called after late cleanup has run. Will remove the current thread from
 * the lookup table again. The boxedThread variable contains a boxed reference
 * to the result of calling pthread_self().
 */
static inline void _didLateUnregisterCurrentThread(NSValue *boxedThread)
{
  /* NB this locked section cannot be protected by an exception handler
   * because the exception handler stores information in the current
   * thread variables ... which causes recursion.
   */
  GS_MUTEX_LOCK(_exitingThreadsLock);
  if (nil != _exitingThreads)
    {
      NSMapRemove(_exitingThreads, (const void*)boxedThread);
    }
  GS_MUTEX_UNLOCK(_exitingThreadsLock);
}

/*
 * Forward declaration of the thread unregistration function
 */
static void
unregisterActiveThread(NSThread *thread);

/**
 * Pthread cleanup call.
 *
 * We should normally not get here ... because threads should exit properly
 * and clean up, so that this function doesn't get called.  However if a
 * thread terminates for some reason without calling the exit method, we
 * we add it to a special lookup table that is used by GSCurrentThread() to
 * obtain the NSThread object.
 * We need to be a bit careful about this regarding object allocation because
 * we must not call into NSAutoreleasePool unless the NSThread object can still
 * be found using GSCurrentThread()
 */
static void GS_WINAPI
exitedThread(void *thread)
{
  if (thread != defaultThread)
    {
      NSValue           *ref;

      if (0 == thread)
	{
	  /* On some systems this is called with a null thread pointer,
	   * so try to get the NSThread object for the current thread.
	   */
	  thread = GS_THREAD_KEY_GET(thread_object_key);
	  if (0 == thread)
	    {
	      return;	// no thread info
	    }
	}
      RETAIN((NSThread*)thread);
      ref = NSValueCreateFromPthread(GS_THREAD_ID_SELF());
      _willLateUnregisterThread(ref, (NSThread*)thread);

      {
        CREATE_AUTORELEASE_POOL(arp);
        NS_DURING
          {
            unregisterActiveThread((NSThread*)thread);
          }
        NS_HANDLER
          {
            DESTROY(arp);
            _didLateUnregisterCurrentThread(ref);
            DESTROY(ref);
            RELEASE((NSThread*)thread);
          }
        NS_ENDHANDLER
        DESTROY(arp);
      }

      /* At this point threre shouldn't be any autoreleased objects lingering
       * around anymore. So we may remove the thread from the lookup table.
       */
      _didLateUnregisterCurrentThread(ref);
      DESTROY(ref);
      RELEASE((NSThread*)thread);
    }
}

/**
 * These functions needed because sending messages to classes is a seriously
 * slow process with gcc and the gnu runtime.
 */
inline NSThread*
GSCurrentThread(void)
{
  NSThread *thr;

  if (NO == keyInitialized)
    {
      if (!GS_THREAD_KEY_INIT(thread_object_key, exitedThread))
        {
          [NSException raise: NSInternalInconsistencyException
                      format: @"Unable to create thread key!"];
        }
      keyInitialized = YES;
    }
  thr = GS_THREAD_KEY_GET(thread_object_key);
  if (nil == thr)
    {
      NSValue *selfThread = NSValueCreateFromPthread(GS_THREAD_ID_SELF());

      /* NB this locked section cannot be protected by an exception handler
       * because the exception handler stores information in the current
       * thread variables ... which causes recursion.
       */
      if (nil != _exitingThreads)
        {
          GS_MUTEX_LOCK(_exitingThreadsLock);
          thr = NSMapGet(_exitingThreads, (const void*)selfThread);
          GS_MUTEX_UNLOCK(_exitingThreadsLock);
        }
      DESTROY(selfThread);
      if (nil == thr)
        {
          GSRegisterCurrentThread();
          thr = GS_THREAD_KEY_GET(thread_object_key);
          if ((nil == defaultThread) && IS_MAIN_PTHREAD)
            {
              defaultThread = RETAIN(thr);
            }
        }
      assert(nil != thr && "No main thread");
    }
  return thr;
}

NSMutableDictionary*
GSDictionaryForThread(NSThread *t)
{
  if (nil == t)
    {
      t = GSCurrentThread();
    }
  return [t threadDictionary];
}

/**
 * Fast access function for thread dictionary of current thread.
 */
NSMutableDictionary*
GSCurrentThreadDictionary(void)
{
  return GSDictionaryForThread(nil);
}

/*
 * Callback function to send notifications on becoming multi-threaded.
 */
static void
gnustep_base_thread_callback(void)
{
  static gs_mutex_t  threadLock = GS_MUTEX_INIT_STATIC;
  /*
   * Protect this function with locking ... to avoid any possibility
   * of multiple threads registering with the system simultaneously,
   * and so that all NSWillBecomeMultiThreadedNotifications are sent
   * out before any second thread can interfere with anything.
   */
  if (entered_multi_threaded_state == NO)
    {
      GS_MUTEX_LOCK(threadLock);
      if (entered_multi_threaded_state == NO)
	{
	  /*
	   * For apple compatibility ... and to make things easier for
	   * code called indirectly within a will-become-multi-threaded
	   * notification handler, we set the flag to say we are multi
	   * threaded BEFORE sending the notifications.
	   */
	  entered_multi_threaded_state = YES;
	  /*
	   * Enter pool after setting flag, because -[NSAutoreleasePool
	   * allocWithZone:] calls GSCurrentThread(), which may end up
	   * calling this function, which would cause a deadlock.
	   */
	  ENTER_POOL
	  NS_DURING
	    {
	      [GSPerformHolder class];	// Force initialization

	      /*
	       * Post a notification if this is the first new thread
	       * to be created.
	       * Won't work properly if threads are not all created
	       * by this class, but it's better than nothing.
	       */
	      if (nc == nil)
		{
		  nc = RETAIN([NSNotificationCenter defaultCenter]);
		}
#if	!defined(HAVE_INITIALIZE)
	      if (NO == [[NSUserDefaults standardUserDefaults]
		boolForKey: @"GSSilenceInitializeWarning"])
		{
		  NSLog(@"WARNING your program is becoming multi-threaded, but you are using an ObjectiveC runtime library which does not have a thread-safe implementation of the +initialize method. Please see README.initialize for more information.");
		}
#endif
	      [nc postNotificationName: NSWillBecomeMultiThreadedNotification
				object: nil
			      userInfo: nil];
	    }
	  NS_HANDLER
	    {
	      fprintf(stderr,
"ALERT ... exception while becoming multi-threaded ... system may not be\n"
"properly initialised.\n");
	      fflush(stderr);
	    }
	  NS_ENDHANDLER
	  LEAVE_POOL
	}
      GS_MUTEX_UNLOCK(threadLock);
    }
}

@implementation NSThread (Activation)
- (void) _makeThreadCurrent
{
  /* NB. We must set up the pointer to the new NSThread instance from
   * pthread specific memory before we do anything which might need to
   * check what the current thread is (like getting the ID)!
   */
  GS_THREAD_KEY_SET(thread_object_key, self);
  threadID = GSPrivateThreadID();
  GS_MUTEX_LOCK(_activeLock);
  /* The hash table is created lazily/late so that the NSThread
   * +initialize method can be called without causing other
   * classes to be initialized.
   * NB this locked section cannot be protected by an exception handler
   * because the exception handler stores information in the current
   * thread variables ... which causes recursion.
   */
  if (nil == _activeThreads)
    {
      _activeThreads = NSCreateHashTable(
	NSNonRetainedObjectHashCallBacks, 100);
    }
  NSHashInsert(_activeThreads, (const void*)self);
  GS_MUTEX_UNLOCK(_activeLock);
}
@end

@implementation NSThread

static void
setThreadForCurrentThread(NSThread *t)
{
  [t _makeThreadCurrent];
  gnustep_base_thread_callback();
}

static void
unregisterActiveThread(NSThread *thread)
{
  if (thread->_active == YES)
    {
      /* Let observers know this thread is exiting.
       */
      ENTER_POOL
      if (nc == nil)
	{
	  nc = RETAIN([NSNotificationCenter defaultCenter]);
	}
      [nc postNotificationName: NSThreadWillExitNotification
			object: thread
		      userInfo: nil];

      /* Set the thread to be finished *after* notification it will exit.
       * This is the order OSX 10.15.4 does it (May 2020).
       */
      thread->_active = NO;
      thread->_finished = YES;

      [(GSRunLoopThreadInfo*)thread->_runLoopInfo invalidate];
      LEAVE_POOL
      RELEASE(thread);
      GS_THREAD_KEY_SET(thread_object_key, nil);
    }
}

+ (NSArray*) callStackReturnAddresses
{
  GSStackTrace          *stack;
  NSArray               *addrs;

  stack = [GSStackTrace new];
  [stack trace];
  addrs = RETAIN([stack addresses]);
  RELEASE(stack);
  return AUTORELEASE(addrs);
}

+ (BOOL) _createThreadForCurrentPthread
{
  NSThread	*t = GS_THREAD_KEY_GET(thread_object_key);

  if (t == nil)
    {
      t = [self new];
      t->_active = YES;
      [t _makeThreadCurrent];
      GS_CONSUMED(t);
      if (defaultThread != nil && t != defaultThread)
        {
          gnustep_base_thread_callback();
        }
      return YES;
    }
  return NO;
}

+ (NSThread*) currentThread
{
  return GSCurrentThread();
}

+ (void) detachNewThreadSelector: (SEL)aSelector
		        toTarget: (id)aTarget
                      withObject: (id)anArgument
{
  NSThread	*thread;

  /*
   * Create the new thread.
   */
  thread = [[NSThread alloc] initWithTarget: aTarget
                                   selector: aSelector
                                     object: anArgument];

  [thread start];
  RELEASE(thread);
}

+ (void) exit
{
  NSThread	*t;

  t = GSCurrentThread();
  if (t->_active == YES)
    {
      unregisterActiveThread(t);

      if (t == defaultThread || defaultThread == nil)
	{
	  /* For the default thread, we exit the process.
	   */
	  exit(0);
	}
      else
	{
#if GS_USE_WIN32_THREADS_AND_LOCKS
          _endthread();
#else
          pthread_exit(NULL);
#endif
	}
    }
}

/*
 * Class initialization
 */
+ (void) initialize
{
  if (self == [NSThread class])
    {
      if (NO == keyInitialized)
        {
          if (!GS_THREAD_KEY_INIT(thread_object_key, exitedThread))
            {
              [NSException raise: NSInternalInconsistencyException
                          format: @"Unable to create thread key!"];
            }
          keyInitialized = YES;
        }
      /* Ensure that the default thread exists.
       * It's safe to create a lock here (since [NSObject+initialize]
       * creates locks, and locks don't depend on any other class),
       * but we want to avoid initialising other classes while we are
       * initialising NSThread.
       */
      threadClass = self;
      GSCurrentThread();
    }
}

+ (BOOL) isMainThread
{
  return (GSCurrentThread() == defaultThread ? YES : NO);
}

+ (BOOL) isMultiThreaded
{
  return entered_multi_threaded_state;
}

+ (NSThread*) mainThread
{
  return defaultThread;
}

/**
 * Set the priority of the current thread.  This is a value in the
 * range 0.0 (lowest) to 1.0 (highest) which is mapped to the underlying
 * system priorities.
 */
+ (BOOL) setThreadPriority: (double)pri
{
#if GS_USE_WIN32_THREADS_AND_LOCKS
  // convert [0.0,1.0] priority to Windows defines
  int winPri;
  if (pri <= 0.0) {
    winPri = THREAD_PRIORITY_IDLE;
  } else if (pri <= 0.25) {
    winPri = THREAD_PRIORITY_LOWEST;
  } else if (pri < 0.5) {
    winPri = THREAD_PRIORITY_BELOW_NORMAL;
  } else if (pri >= 1.0) {
    winPri = THREAD_PRIORITY_TIME_CRITICAL;
  } else if (pri >= 0.75) {
    winPri = THREAD_PRIORITY_HIGHEST;
  } else if (pri > 0.5) {
    winPri = THREAD_PRIORITY_ABOVE_NORMAL;
  } else {
    winPri = THREAD_PRIORITY_NORMAL;
  }

  if (!SetThreadPriority(GetCurrentThread(), winPri)) {
    NSLog(@"Failed to set thread priority %d: %@", winPri, [NSError _last]);
    return NO;
  }
  return YES;
#elif defined(__ANDROID__)
/* Android's pthread_setschedparam is currently broken, as it checks
 * if the priority is in the range of the system's min and max
 * priorities. The interval bounds are queried with `sched_get_priority_min`,
 * and `sched_get_priority_max` which just return 0, regardless of the
 * specified scheduling policy.
 *
 * The solution is to use `setpriority` to set the thread
 * priority. This is possible because on Linux, it is not a per-process setting
 * as specified by POSIX but a per-thread setting (See the `Bugs` section in `setpriority`).
 *
 * Android's internal implementation also relies on this behavior, so it
 * is safe to use it here.
 */

  // Clamp pri into the required range.
  if (pri > 1) { pri = 1; }
  if (pri < 0) { pri = 0; }

  // Convert [0.0, 1.0] to [-20, 19] range where -20 is the highest
  // and 19 the lowest priority.
  int priority = (int)(-20 + (1-pri) * 39);
  if (setpriority(PRIO_PROCESS, 0, priority) == -1)
  {
    NSLog(@"Failed to set thread priority %d: %s", priority, strerror(errno));
    return NO;
  }
  return YES;
#elif defined(_POSIX_THREAD_PRIORITY_SCHEDULING) && (_POSIX_THREAD_PRIORITY_SCHEDULING > 0)
  int res;
  int	policy;
  struct sched_param param;

  // Clamp pri into the required range.
  if (pri > 1) { pri = 1; }
  if (pri < 0) { pri = 0; }

  res = pthread_getschedparam(pthread_self(), &policy, &param);
  if (res == 0)
    {
      int min = sched_get_priority_min(policy);
      int max = sched_get_priority_max(policy);
      if (min == max) {
        // priority not settable => fail silently
        return NO;
      }

      // Scale pri based on the range of the host system.
      pri = min + pri * (max - min);

      param.sched_priority = pri;
      res = pthread_setschedparam(pthread_self(), policy, &param);
    }

  if (res != 0) {
    NSLog(@"Failed to set thread priority %f: %d", pri, res);
    return NO;
  }

  return YES;
#else
  return NO;
#endif
}

+ (void) sleepForTimeInterval: (NSTimeInterval)ti
{
  GSSleepUntilIntervalSinceReferenceDate(GSPrivateTimeNow() + ti);
}

/**
 * Delaying a thread ... pause until the specified date.
 */
+ (void) sleepUntilDate: (NSDate*)date
{
  GSSleepUntilIntervalSinceReferenceDate([date timeIntervalSinceReferenceDate]);
}


/**
 * Return the priority of the current thread.
 */
+ (double) threadPriority
{
  double pri = 0;

#if GS_USE_WIN32_THREADS_AND_LOCKS
  // convert [0.0,1.0] priority to Windows defines
  int winPri = GetThreadPriority(GetCurrentThread());
  if (winPri == THREAD_PRIORITY_ERROR_RETURN) {
    NSLog(@"Failed to get thread priority: %@", [NSError _last]);
    return pri;
  }
  
  switch (winPri)
    {
      case THREAD_PRIORITY_IDLE:
        pri = 0.0;
        break;
      case THREAD_PRIORITY_LOWEST:
        pri = 0.2;
        break;
      case THREAD_PRIORITY_BELOW_NORMAL:
        pri = 0.4;
        break;
      case THREAD_PRIORITY_TIME_CRITICAL:
        pri = 1.0;
        break;
      case THREAD_PRIORITY_HIGHEST:
        pri = 0.8;
        break;
      case THREAD_PRIORITY_ABOVE_NORMAL:
        pri = 0.6;
        break;
      case THREAD_PRIORITY_NORMAL:
        pri = 0.5;
        break;
      default:
        NSLog(@"Unknown thread priority: %d", winPri);
        break;
    }
#elif defined(__ANDROID__)
/* See notes in setThreadPriority
 */
  int priority = getpriority(PRIO_PROCESS, 0);
  if (priority == -1)
  {
    NSLog(@"Failed to get thread priority: %s", strerror(errno));
    return pri;
  }

  // Convert [-20, 19] to [0.0, 1.0] range
  pri = 1 - (priority + 20) / 39.0;
#elif defined(_POSIX_THREAD_PRIORITY_SCHEDULING) && (_POSIX_THREAD_PRIORITY_SCHEDULING > 0)
  int res;
  int policy;
  struct sched_param param;

  res = pthread_getschedparam(pthread_self(), &policy, &param);
  if (res == 0)
    {
      int min = sched_get_priority_min(policy);
      int max = sched_get_priority_max(policy);
      if (min != max) /* avoid division by zero */
        {
          pri = param.sched_priority;

          // Scale pri based on the range of the host system.
          pri = (pri - min) / (max - min);
        }
    }
  else
    {
      NSLog(@"Failed to get thread priority: %d", res);
    }
#else
#warning Your pthread implementation does not support thread priorities
#endif

  return pri;
}

/*
 * Thread instance methods.
 */

- (void) cancel
{
  _cancelled = YES;
}

- (void) dealloc
{
  int   retries = 0;

  if (_active == YES)
    {
      [NSException raise: NSInternalInconsistencyException
		  format: @"Deallocating an active thread without [+exit]!"];
    }
  DESTROY(_runLoopInfo);
  DESTROY(_thread_dictionary);
  DESTROY(_target);
  DESTROY(_arg);
  DESTROY(_name);
  DESTROY(stringCollatorCache);
  if (_autorelease_vars.pool_cache != 0)
    {
      [NSAutoreleasePool _endThread: self];
    }

  while ((_thread_dictionary != nil || _runLoopInfo != nil) && retries++ < 10)
    {
      /* Try again.
       */
      DESTROY(_runLoopInfo);
      DESTROY(_thread_dictionary);
      if (_autorelease_vars.pool_cache != 0)
	{
	  [NSAutoreleasePool _endThread: self];
	}
    }

  if (_runLoopInfo != nil)
    {
      NSLog(@"Oops - leak - run loop is %@", _runLoopInfo);
      if (_autorelease_vars.pool_cache != 0)
        {
          [NSAutoreleasePool _endThread: self];
        }
    }
  if (_thread_dictionary != nil)
    {
      NSLog(@"Oops - leak - thread dictionary is %@", _thread_dictionary);
      if (_autorelease_vars.pool_cache != 0)
        {
          [NSAutoreleasePool _endThread: self];
        }
    }
  DESTROY(_gcontext);
  if (_activeThreads)
    {
      GS_MUTEX_LOCK(_activeLock);
      NSHashRemove(_activeThreads, self);
      GS_MUTEX_UNLOCK(_activeLock);
    }
  if (GS_EXISTS_INTERNAL)
    {
      pthread_spin_lock(&lockInfo.spin);
      DESTROY(lockInfo.held);
      lockInfo.wait = nil;
      pthread_spin_unlock(&lockInfo.spin);
      pthread_spin_destroy(&lockInfo.spin);
      if (internal != nil)
        {
          GS_DESTROY_INTERNAL(NSThread);
        }
    }
  [super dealloc];
}

- (NSString*) description
{
  return [NSString stringWithFormat: @"%@{name = %@, num = %"PRIuPTR"}",
    [super description], _name, threadID];
}

- (id) init
{
// SetThreadDescription() was added in Windows 10 1607 (Redstone 1)
#if defined(_WIN32) && (NTDDI_VERSION >= NTDDI_WIN10_RS1)
  HANDLE current;
  HRESULT hr;
  PWSTR name;
  NSString *threadName;

  current = GetCurrentThread();
  hr = GetThreadDescription(current, &name);
  if (SUCCEEDED(hr))
    {
      threadName = [NSString stringWithCharacters: (const void *) name length: wcslen(name)];
      ASSIGN(_name, threadName);
      LocalFree(name);
    }
#elif defined(PTHREAD_GETNAME)
  NSString *threadName;
  char name[16];
  int status;

  status = PTHREAD_GETNAME(name, 16);
  if (status == 0)
    {
      threadName = [NSString stringWithCString: name encoding: NSUTF8StringEncoding];
      ASSIGN(_name, threadName);
    }
#endif

  GS_CREATE_INTERNAL(NSThread);
  pthread_spin_init(&lockInfo.spin, 0);
  lockInfo.held = NSCreateHashTable(NSNonOwnedPointerHashCallBacks, 10);
  init_autorelease_thread_vars(&_autorelease_vars);
  return self;
}

- (id) initWithTarget: (id)aTarget
             selector: (SEL)aSelector
               object: (id)anArgument
{
  if (nil != (self = [self init]))
    {
      /* initialize our ivars. */
      _selector = aSelector;
      _target = RETAIN(aTarget);
      _arg = RETAIN(anArgument);
    } 
  return self;
}

- (BOOL) isCancelled
{
  return _cancelled;
}

- (BOOL) isExecuting
{
  return _active;
}

- (BOOL) isFinished
{
  return _finished;
}

- (BOOL) isMainThread
{
  return (self == defaultThread ? YES : NO);
}

- (void) main
{
  if (_active == NO)
    {
      [NSException raise: NSInternalInconsistencyException
                  format: @"[%@-%@] called on inactive thread",
        NSStringFromClass([self class]),
        NSStringFromSelector(_cmd)];
    }

  if (targetIsBlock)
    {
      GSThreadBlock block = (GSThreadBlock)_target;
      CALL_BLOCK_NO_ARGS(block);
    }
  else
    {
      [_target performSelector: _selector withObject: _arg];
    }
}

- (NSString*) name
{
  return _name;
}

- (void) _setName: (NSString *)aName
{
  if ([aName isKindOfClass: [NSString class]])
    {
// SetThreadDescription() was added in Windows 10 1607 (Redstone 1)
#if defined(_WIN32) && (NTDDI_VERSION >= NTDDI_WIN10_RS1)
      HANDLE current;
      const void *utf16String;

      current = GetCurrentThread();
      utf16String = [aName cStringUsingEncoding: NSUnicodeStringEncoding];
      SetThreadDescription(current, utf16String);
#elif defined(PTHREAD_SETNAME)
      int       i;
      char      buf[200];

      if (YES == [aName getCString: buf
                        maxLength: sizeof(buf)
                          encoding: NSUTF8StringEncoding])
        {
          i = strlen(buf);
        }
      else
        {
          /* Too much for buffer ... truncate on a character boundary.
          */
          i = sizeof(buf) - 1;
          if (buf[i] & 0x80)
            {
              while (i > 0 && (buf[i] & 0x80))
                {
                  buf[i--] = '\0';
                }
            }
          else
            {
              buf[i--] = '\0';
            }
        }
      while (i > 0)
        {
          if (PTHREAD_SETNAME(buf) == ERANGE)
            {
              /* Name must be too long ... gnu/linux uses 15 characters
              */
              if (i > 15)
                {
                  NSWarnLog(@"Truncating thread name '%s' to 15 characters"
		    @" due to platform limitations", buf);
                  i = 15;
                }
              else
                {
                  i--;
                }
              /* too long a name ... truncate on a character boundary.
              */
              if (buf[i] & 0x80)
                {
                  while (i > 0 && (buf[i] & 0x80))
                    {
                      buf[i--] = '\0';
                    }
                }
              else
                {
                  buf[i--] = '\0';
                }
            }
          else
            {
              break;    // Success or some other error
            }
        }
#endif
  }
}

- (void) setName: (NSString*)aName
{
  ASSIGN(_name, aName);
  
  if (YES == _active)
    {
      [self performSelector: @selector(_setName:)
                   onThread: self
                 withObject: aName
              waitUntilDone: NO];
    }
}

- (void) setStackSize: (NSUInteger)stackSize
{
  _stackSize = stackSize;
}

- (NSUInteger) stackSize
{
  return _stackSize;
}

/**
 * Trampoline function called to launch the thread
 */
static
#if GS_USE_WIN32_THREADS_AND_LOCKS
void __cdecl
#else
void *
#endif
nsthreadLauncher(void *thread)
{
  NSThread *t = (NSThread*)thread;

  setThreadForCurrentThread(t);

  ENTER_POOL
  /*
   * Let observers know a new thread is starting.
   */
  if (nc == nil)
    {
      nc = RETAIN([NSNotificationCenter defaultCenter]);
    }
  [nc postNotificationName: NSThreadDidStartNotification
		    object: t
		  userInfo: nil];

  [t _setName: [t name]];
  LEAVE_POOL

  [t main];

  [NSThread exit];
  // Not reached
#if !GS_USE_WIN32_THREADS_AND_LOCKS
  return NULL;
#endif
}

- (void) start
{
#if !GS_USE_WIN32_THREADS_AND_LOCKS
  pthread_attr_t	attr;
#endif

  if (_active == YES)
    {
      [NSException raise: NSInternalInconsistencyException
                  format: @"[%@-%@] called on active thread",
        NSStringFromClass([self class]),
        NSStringFromSelector(_cmd)];
    }
  if (_cancelled == YES)
    {
      [NSException raise: NSInternalInconsistencyException
                  format: @"[%@-%@] called on cancelled thread",
        NSStringFromClass([self class]),
        NSStringFromSelector(_cmd)];
    }
  if (_finished == YES)
    {
      [NSException raise: NSInternalInconsistencyException
                  format: @"[%@-%@] called on finished thread",
        NSStringFromClass([self class]),
        NSStringFromSelector(_cmd)];
    }

  /* Make sure the notification is posted BEFORE the new thread starts.
   */
  gnustep_base_thread_callback();

  /* The thread must persist until it finishes executing.
   */
  RETAIN(self);

  /* Mark the thread as active while it's running.
   */
  _active = YES;

  errno = 0;

#if GS_USE_WIN32_THREADS_AND_LOCKS
  if (_beginthread(nsthreadLauncher, _stackSize, self) == -1)
    {
      DESTROY(self);
      [NSException raise: NSInternalInconsistencyException
                  format: @"Unable to detach thread (last error %d)",
                  errno];
    }
#else
  pthread_attr_init(&attr);
  /* Create this thread detached, because we never use the return state from
   * threads.
   */
  pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_DETACHED);
  /* Set the stack size when the thread is created.  Unlike the old setrlimit
   * code, this actually works.
   */
  if (_stackSize > 0)
    {
      pthread_attr_setstacksize(&attr, _stackSize);
    }
  if (pthread_create(&pthreadID, &attr, nsthreadLauncher, self))
    {
      DESTROY(self);
      [NSException raise: NSInternalInconsistencyException
                  format: @"Unable to detach thread (last error %@)",
                  [NSError _last]];
    }
#endif
}

/**
 * Return the thread dictionary.  This dictionary can be used to store
 * arbitrary thread specific data.<br />
 * NB. This cannot be autoreleased, since we cannot be sure that the
 * autorelease pool for the thread will continue to exist for the entire
 * life of the thread!
 */
- (NSMutableDictionary*) threadDictionary
{
  if (_thread_dictionary == nil)
    {
      _thread_dictionary = [NSMutableDictionary new];
    }
  return _thread_dictionary;
}

- (id) _stringCollatorCache
{
  return (id)stringCollatorCache;
}
- (void) _setStringCollatorCache: (id) cache
{
  ASSIGN(stringCollatorCache, cache);
}

@end



@implementation NSThread (GSLockInfo)

static NSString *
lockInfoErr(NSString *str)
{
  if (disableTraceLocks)
    {
      return nil;
    }
  return str;
}

- (NSString *) mutexDrop: (id)mutex
{
  if (GS_EXISTS_INTERNAL)
    {
      GSLockInfo        *li = &lockInfo;
      int               err;

      if (YES == disableTraceLocks) return nil;
      err = pthread_spin_lock(&li->spin);
      if (EDEADLK == err) return lockInfoErr(@"thread spin lock deadlocked");
      if (EINVAL == err) return lockInfoErr(@"thread spin lock invalid");

      if (mutex == li->wait)
        {
          /* The mutex was being waited for ... simply remove it.
           */
          li->wait = nil;
        }
      else if (NSHashGet(li->held, (void*)mutex) == (void*)mutex)
        {
          GSStackTrace  *stck = [mutex stack];

          /* The mutex was being held ... if the recursion count was zero
           * we remove it (otherwise the count is decreased).
           */
          if (stck->recursion-- == 0)
            {
              NSHashRemove(li->held, (void*)mutex);
// fprintf(stderr, "%lu: Drop %p (final) %lu\n", (unsigned long)_threadID, mutex, [li->held count]);
            }
          else
            {
// fprintf(stderr, "%lu: Drop %p (%lu) %lu\n", (unsigned long)threadID, mutex, (unsigned long)stck->recursion, [li->held count]);
            }
        }
      else
        {
// fprintf(stderr, "%lu: Drop %p (bad) %lu\n", (unsigned long)threadID, mutex, [li->held count]);
          pthread_spin_unlock(&li->spin);
          return lockInfoErr(
            @"attempt to unlock mutex not locked by this thread");
        }
      pthread_spin_unlock(&li->spin);
      return nil;
    }
  return lockInfoErr(@"thread not active");
}

- (NSString *) mutexHold: (id)mutex
{
  if (GS_EXISTS_INTERNAL)
    {
      GSLockInfo        *li = &lockInfo;
      int               err;

      if (YES == disableTraceLocks) return nil;
      err = pthread_spin_lock(&li->spin);
      if (EDEADLK == err) return lockInfoErr(@"thread spin lock deadlocked");
      if (EINVAL == err) return lockInfoErr(@"thread spin lock invalid");
      if (nil == mutex)
        {
          mutex = li->wait;
          if (nil == mutex)
            {
              pthread_spin_unlock(&li->spin);
              return lockInfoErr(@"attempt to hold nil mutex");
            }
        }
      else if (nil != li->wait && mutex != li->wait)
        {
          pthread_spin_unlock(&li->spin);
          return lockInfoErr(@"attempt to hold mutex without waiting for it");
        }
      if (NSHashGet(li->held, (void*)mutex) == NULL)
        {
          [[mutex stack] trace];                // Get current strack trace
          NSHashInsert(li->held, (void*)mutex);
// fprintf(stderr, "%lu: Hold %p (initial) %lu\n", (unsigned long)threadID, mutex, [li->held count]);
        }
      else
        {
          GSStackTrace  *stck = [mutex stack];

          stck->recursion++;
// fprintf(stderr, "%lu: Hold %p (%lu) %lu\n", (unsigned long)threadID, mutex, (unsigned long)stck->recursion, [li->held count]);
        }
      li->wait = nil;
      pthread_spin_unlock(&li->spin);
      return nil;
    }
  return lockInfoErr(@"thread not active");
}

- (NSString *) mutexWait: (id)mutex
{
  if (GS_EXISTS_INTERNAL)
    {
      NSMutableArray    *dependencies;
      id                want;
      BOOL              done;
      GSLockInfo        *li = &lockInfo;
      BOOL              owned = NO;
      int               err;

      if (YES == disableTraceLocks) return nil;
      err = pthread_spin_lock(&li->spin);
      if (EDEADLK == err) return lockInfoErr(@"thread spin lock deadlocked");
      if (EINVAL == err) return lockInfoErr(@"thread spin lock invalid");
      if (nil != li->wait)
        {
          NSString      *msg = [NSString stringWithFormat:
            @ "trying to lock %@ when already trying to lock %@",
            mutex, li->wait];
          pthread_spin_unlock(&li->spin);
          return lockInfoErr(msg);
        }
      li->wait = mutex;
      if (nil != NSHashGet(li->held, (const void*)mutex))
        {
          owned = YES;
        }
      pthread_spin_unlock(&li->spin);
// fprintf(stderr, "%lu: Wait %p\n", (unsigned long)_threadID, mutex);
      if (YES == owned && [mutex isKindOfClass: [NSRecursiveLock class]])
        {
          return nil;   // We can't deadlock on a recursive lock we own
        }

      /* While checking for deadlocks we don't want threads created/destroyed
       * So we hold the lock to prevent thread activity changes.
       * This also ensures that no more than one thread can be checking for
       * deadlocks at a time (no interference between checks).
       */
      GS_MUTEX_LOCK(_activeLock);

      /* As we isolate dependencies (a thread holding the lock another thread
       * is waiting for) we disable locking in each thread and record the
       * thread in a hash table.  Once we have determined all the dependencies
       * we can re-enable locking in each of the threads.
       */
      if (nil == _activeBlocked)
        {
          _activeBlocked = NSCreateHashTable(
            NSNonRetainedObjectHashCallBacks, 100);
        }

      dependencies = nil;
      want = mutex;
      done = NO;

      while (NO == done)
        {
          NSHashEnumerator	enumerator;
          NSThread              *found = nil;
          BOOL                  foundWasLocked = NO;
          NSThread              *th;

          /* Look for a thread which is holding the mutex we are currently
           * interested in.  We are only interested in thread which are
           * themselves waiting for a lock (if they aren't waiting then
           * they can't be part of a deadlock dependency list).
           */
          enumerator = NSEnumerateHashTable(_activeThreads);
          while ((th = NSNextHashEnumeratorItem(&enumerator)) != nil)
            {
              GSLockInfo        *info = &GSIVar(th, _lockInfo);

              if (YES == th->_active && nil != info->wait)
                {
                  BOOL          wasLocked;

                  if (th == self
                    || NULL != NSHashGet(_activeBlocked, (const void*)th))
                    {
                      /* Don't lock ... this is the current thread or is
                       * already in the set of blocked threads.
                       */
                      wasLocked = YES;
                    }
                  else
                    {
                      pthread_spin_lock(&info->spin);
                      wasLocked = NO;
                    }
                  if (nil != info->wait
                    && nil != (id)NSHashGet(info->held, (const void*)want))
                    {
                      /* This thread holds the lock we are interested in and
                       * is waiting for another lock.
                       * We therefore record the details in the dependency list
                       * and will go on to look for the thread this found one
                       * depends on.
                       */
                      found = th;
                      foundWasLocked = wasLocked;
                      want = info->wait;
                      if (nil == dependencies)
                        {
                          dependencies = [NSMutableArray new];
                        }
                      [dependencies addObject: found];  // thread
                      [dependencies addObject: want];   // mutex
                      /* NB. breaking out here holds the spin lock so that
                       * the lock state of each dependency thread is
                       * preserved (if we don't have a deadlock, we get a
                       * consistent snapshot of the threads and their locks).
                       * We therefore have to unlock the threads when done.
                       */
                      break;
                    }
                  /* This thread did not hold the lock we are interested in,
                   * so we can unlock it (if necessary) and check another.
                   */
                  if (NO == wasLocked)
                    {
                      pthread_spin_unlock(&info->spin);
                    }
                }
            }
          NSEndHashTableEnumeration(&enumerator);
          if (nil == found)
            {
              /* There is no thread blocked on the mutex we are checking,
               * so we can't have a deadlock.
               */
              DESTROY(dependencies);
              done = YES;
            }
          else if (foundWasLocked)
            {
              /* The found thread is the current one or in the blocked set
               * so we have a deadlock.
               */
              done = YES;
            }
          else
            {
              /* Record the found (and locked) thread and continue
               * to find the next dependency.
               */
              NSHashInsert(_activeBlocked, (const void*)found);
            }
        }

      /* Ensure any locked threads are unlocked again.
       */
      if (NSCountHashTable(_activeBlocked) > 0)
        {
          NSHashEnumerator	enumerator;
          NSThread              *th;

          enumerator = NSEnumerateHashTable(_activeThreads);
          while ((th = NSNextHashEnumeratorItem(&enumerator)) != nil)
            {
              GSLockInfo        *info = &GSIVar(th, _lockInfo);

              pthread_spin_unlock(&info->spin);
            }
          NSEndHashTableEnumeration(&enumerator);
          NSResetHashTable(_activeBlocked);
        }

      /* Finished check ... re-enable thread activity changes.
       */
      GS_MUTEX_UNLOCK(_activeLock);


      if (nil != dependencies)
        {
          GSStackTrace          *stack;
          NSUInteger            count;
          NSUInteger            index = 0;
          NSMutableString       *m;

          disableTraceLocks = YES;
          m = [NSMutableString stringWithCapacity: 1000];
          stack = [GSStackTrace new];
          [stack trace];
          [m appendFormat: @"Deadlock on %@ at\n  %@\n",
            mutex, [stack symbols]];
          RELEASE(stack);
          count = [dependencies count];
          while (index < count)
            {
              NSArray           *symbols;
              NSThread          *thread;
              NSUInteger        frameCount;

              thread = [dependencies objectAtIndex: index++];
              mutex = [dependencies objectAtIndex: index++];
              symbols = [[mutex stack] symbols];
              frameCount = [symbols count];
              if (frameCount > 0)
                {
                  NSUInteger    i;

                  [m appendFormat: @"  depends on %@\n  blocked by %@\n  at\n",
                    mutex, thread];
                  for (i = 0; i < frameCount; i++)
                    {
                      [m appendFormat: @"    %@\n", [symbols objectAtIndex: i]];
                    }
                }
              else
                {
                  [m appendFormat: @"  depends on %@\n  blocked by %@\n",
                    mutex, thread];
                }
            }
          DESTROY(dependencies);
          /* NB. Return m directly because we have turned off tracing to
           * avoid recursion, and don't want lockInfoErr() to stop the
           * error being ruturned.
           */
          return m;
        }
      return nil;
    }
  return lockInfoErr(@"thread not active");
}

@end



@implementation GSRunLoopThreadInfo
- (void) addPerformer: (id)performer
{
  BOOL  signalled = NO;

  [lock lock];
#if defined(_WIN32)
  if (INVALID_HANDLE_VALUE != event)
    {
      if (SetEvent(event) == 0)
        {
          NSLog(@"Set event failed - %@", [NSError _last]);
        }
      else
        {
          signalled = YES;
        }
    }
#else
{
  NSTimeInterval        start = 0.0;

  /* The write could concievably fail if the pipe is full.
   * In that case we need to release the lock temporarily to allow the other
   * thread to consume data from the pipe.  It's possible that the thread
   * and its runloop might stop during that ... so we need to check that
   * outputFd is still valid.
   */
  while (outputFd >= 0
    && NO == (signalled = (write(outputFd, "0", 1) == 1) ? YES : NO))
    {
      NSTimeInterval    now = [NSDate timeIntervalSinceReferenceDate];

      if (0.0 == start)
        {
          start = now;
        }
      else if (now - start >= 1.0)
        {
          NSLog(@"Unable to signal %@ within a second; blocked?", self);
          break;
        }
      [lock unlock];
      [lock lock];
    }
}
#endif
  if (YES == signalled)
    {
      [performers addObject: performer];
    }
  [lock unlock];
  if (NO == signalled)
    {
      /* We failed to add the performer ... so we must invalidate it in
       * case there is code waiting for it to complete.
       */
      [performer invalidate];
    }
}

- (void) dealloc
{
  [self invalidate];
  DESTROY(lock);
  DESTROY(loop);
  [super dealloc];
}

- (id) init
{
#ifdef _WIN32
  if ((event = CreateEvent(NULL, TRUE, FALSE, NULL)) == INVALID_HANDLE_VALUE)
    {
      DESTROY(self);
      [NSException raise: NSInternalInconsistencyException
        format: @"Failed to create event to handle perform in thread"];
    }
#else
  int	fd[2];

  if (pipe(fd) == 0)
    {
      int	e;

      inputFd = fd[0];
      outputFd = fd[1];
      if ((e = fcntl(inputFd, F_GETFL, 0)) >= 0)
	{
	  e |= NBLK_OPT;
	  if (fcntl(inputFd, F_SETFL, e) < 0)
	    {
	      [NSException raise: NSInternalInconsistencyException
		format: @"Failed to set non block flag for perform in thread"];
	    }
	}
      else
	{
	  [NSException raise: NSInternalInconsistencyException
	    format: @"Failed to get non block flag for perform in thread"];
	}
      if ((e = fcntl(outputFd, F_GETFL, 0)) >= 0)
	{
	  e |= NBLK_OPT;
	  if (fcntl(outputFd, F_SETFL, e) < 0)
	    {
	      [NSException raise: NSInternalInconsistencyException
		format: @"Failed to set non block flag for perform in thread"];
	    }
	}
      else
	{
	  [NSException raise: NSInternalInconsistencyException
	    format: @"Failed to get non block flag for perform in thread"];
	}
    }
  else
    {
      DESTROY(self);
      [NSException raise: NSInternalInconsistencyException
        format: @"Failed to create pipe to handle perform in thread"];
    }
#endif
  lock = [NSLock new];
  performers = [NSMutableArray new];
  return self;
}

- (void) invalidate
{
  NSArray       *p;

  [lock lock];
  p = AUTORELEASE(performers);
  performers = nil;
#ifdef _WIN32
  if (event != INVALID_HANDLE_VALUE)
    {
      CloseHandle(event);
      event = INVALID_HANDLE_VALUE;
    }
#else
  if (inputFd >= 0)
    {
      close(inputFd);
      inputFd = -1;
    }
  if (outputFd >= 0)
    {
      close(outputFd);
      outputFd = -1;
    }
#endif
  [lock unlock];
  [p makeObjectsPerformSelector: @selector(invalidate)];
}

- (void) fire
{
  NSArray	*toDo;
  unsigned int	i;
  unsigned int	c;

  [lock lock];
#if defined(_WIN32)
  if (event != INVALID_HANDLE_VALUE)
    {
      if (ResetEvent(event) == 0)
        {
          NSLog(@"Reset event failed - %@", [NSError _last]);
        }
    }
#else
  if (inputFd >= 0)
    {
      char	buf[BUFSIZ];

      /* We don't care how much we read.  If there have been multiple
       * performers queued then there will be multiple bytes available,
       * but we always handle all available performers, so we can also
       * read all available bytes.
       * The descriptor is non-blocking ... so it's safe to ask for more
       * bytes than are available.
       */
      while (read(inputFd, buf, sizeof(buf)) > 0)
	;
    }
#endif

  c = [performers count];
  if (0 == c)
    {
      /* We deal with all available performers each time we fire, so
       * it's likely that we will fire when we have no performers left.
       * In that case we can skip the copying and emptying of the array.
       */
      [lock unlock];
      return;
    }
  toDo = [NSArray arrayWithArray: performers];
  [performers removeAllObjects];
  [lock unlock];

  for (i = 0; i < c; i++)
    {
      GSPerformHolder	*h = [toDo objectAtIndex: i];

      [loop performSelector: @selector(fire)
		     target: h
		   argument: nil
		      order: 0
		      modes: [h modes]];
    }
}
@end

GSRunLoopThreadInfo *
GSRunLoopInfoForThread(NSThread *aThread)
{
  GSRunLoopThreadInfo   *info;

  if (aThread == nil)
    {
      aThread = GSCurrentThread();
    }
  if (aThread->_runLoopInfo == nil)
    {
      static gs_mutex_t	infoLock = GS_MUTEX_INIT_STATIC;

      GS_MUTEX_LOCK(infoLock);
      if (aThread->_runLoopInfo == nil)
        {
          aThread->_runLoopInfo = [GSRunLoopThreadInfo new];
	}
      GS_MUTEX_UNLOCK(infoLock);
    }
  info = aThread->_runLoopInfo;
  return info;
}

@implementation GSPerformHolder

+ (GSPerformHolder*) newForReceiver: (id)r
			   argument: (id)a
			   selector: (SEL)s
			      modes: (NSArray*)m
			       lock: (NSConditionLock*)l
{
  GSPerformHolder	*h;

  h = (GSPerformHolder*)NSAllocateObject(self, 0, NSDefaultMallocZone());
  h->receiver = RETAIN(r);
  h->argument = RETAIN(a);
  h->selector = s;
  h->modes = RETAIN(m);
  h->lock = l;

  return h;
}

- (void) dealloc
{
  DESTROY(exception);
  DESTROY(receiver);
  DESTROY(argument);
  DESTROY(modes);
  if (lock != nil)
    {
      [lock lock];
      [lock unlockWithCondition: 1];
      lock = nil;
    }
  NSDeallocateObject(self);
  GSNOSUPERDEALLOC;
}

- (NSString*) description
{
  return [[super description] stringByAppendingFormat: @" [%s %s]",
    class_getName(object_getClass(receiver)), sel_getName(selector)];
}

- (void) fire
{
  GSRunLoopThreadInfo   *threadInfo;

  if (receiver == nil)
    {
      return;	// Already fired!
    }
  threadInfo = GSRunLoopInfoForThread(GSCurrentThread());
  [threadInfo->loop cancelPerformSelectorsWithTarget: self];
  NS_DURING
    {
      [receiver performSelector: selector withObject: argument];
    }
  NS_HANDLER
    {
      ASSIGN(exception, localException);
      if (nil == lock)
        {
          NSLog(@"*** NSRunLoop ignoring exception '%@' (reason '%@') "
            @"raised during perform in other thread... with receiver %p (%s) "
            @"and selector '%s'",
            [localException name], [localException reason], receiver,
            class_getName(object_getClass(receiver)),
            sel_getName(selector));
        }
    }
  NS_ENDHANDLER
  DESTROY(receiver);
  DESTROY(argument);
  DESTROY(modes);
  if (lock != nil)
    {
      NSConditionLock	*l = lock;

      [lock lock];
      lock = nil;
      [l unlockWithCondition: 1];
    }
}

- (void) invalidate
{
  if (invalidated == NO)
    {
      invalidated = YES;
      DESTROY(receiver);
      if (lock != nil)
        {
          NSConditionLock	*l = lock;

          [lock lock];
          lock = nil;
          [l unlockWithCondition: 1];
        }
    }
}

- (BOOL) isInvalidated
{
  return invalidated;
}

- (NSArray*) modes
{
  return modes;
}
@end

@implementation	NSObject (NSThreadPerformAdditions)

- (void) performSelectorOnMainThread: (SEL)aSelector
			  withObject: (id)anObject
		       waitUntilDone: (BOOL)aFlag
			       modes: (NSArray*)anArray
{
  /* It's possible that this method could be called before the NSThread
   * class is initialised, so we check and make sure it's initiailised
   * if necessary.
   */
  if (defaultThread == nil)
    {
      [NSThread currentThread];
    }
  [self performSelector: aSelector
               onThread: defaultThread
             withObject: anObject
          waitUntilDone: aFlag
                  modes: anArray];
}

- (void) performSelectorOnMainThread: (SEL)aSelector
			  withObject: (id)anObject
		       waitUntilDone: (BOOL)aFlag
{
  [self performSelectorOnMainThread: aSelector
			 withObject: anObject
		      waitUntilDone: aFlag
			      modes: commonModes()];
}

- (void) performSelector: (SEL)aSelector
                onThread: (NSThread*)aThread
              withObject: (id)anObject
           waitUntilDone: (BOOL)aFlag
                   modes: (NSArray*)anArray
{
  GSRunLoopThreadInfo   *info;
  NSThread	        *t;

  if ([anArray count] == 0)
    {
      return;
    }

  t = GSCurrentThread();
  if (aThread == nil)
    {
      aThread = t;
    }
  info = GSRunLoopInfoForThread(aThread);
  if (t == aThread)
    {
      /* Perform in current thread.
       */
      if (aFlag == YES || info->loop == nil)
	{
          /* Wait until done or no run loop.
           */
	  [self performSelector: aSelector withObject: anObject];
	}
      else
	{
          /* Don't wait ... schedule operation in run loop.
           */
	  [info->loop performSelector: aSelector
                               target: self
                             argument: anObject
                                order: 0
                                modes: anArray];
	}
    }
  else
    {
      GSPerformHolder   *h;
      NSConditionLock	*l = nil;

      if ([aThread isFinished] == YES)
        {
          [NSException raise: NSInternalInconsistencyException
            format: @"perform [%@-%@] attempted on finished thread (%@)",
            NSStringFromClass([self class]),
            NSStringFromSelector(aSelector),
            aThread];
        }
      if (aFlag == YES)
	{
	  l = [[NSConditionLock alloc] init];
	}

      h = [GSPerformHolder newForReceiver: self
				 argument: anObject
				 selector: aSelector
				    modes: anArray
				     lock: l];
      [info addPerformer: h];
      if (l != nil)
	{
          [l lockWhenCondition: 1];
	  [l unlock];
	  RELEASE(l);
          if ([h isInvalidated] == NO)
            {
              /* If we have an exception passed back from the remote thread,
               * re-raise it.
               */
              if (nil != h->exception)
                {
                  NSException       *e = AUTORELEASE(RETAIN(h->exception));

                  RELEASE(h);
                  [e raise];
                }
            }
	}
      RELEASE(h);
    }
}

- (void) performSelector: (SEL)aSelector
                onThread: (NSThread*)aThread
              withObject: (id)anObject
           waitUntilDone: (BOOL)aFlag
{
  [self performSelector: aSelector
               onThread: aThread
             withObject: anObject
          waitUntilDone: aFlag
                  modes: commonModes()];
}

- (void) performSelectorInBackground: (SEL)aSelector
                          withObject: (id)anObject
{
  [NSThread detachNewThreadSelector: aSelector
                           toTarget: self
                         withObject: anObject];
}

@end

@implementation NSThread (BlockAdditions)

+ (void) detachNewThreadWithBlock: (GSThreadBlock)block
{
  NSThread	*thread;

  thread = [[NSThread alloc] initWithBlock: block];
  [thread start];

  RELEASE(thread);
}

- (instancetype) initWithBlock: (GSThreadBlock)block
{
  if (nil != (self = [self init]))
    {
      targetIsBlock = YES;
      /* Copy block to heap */
      _target = _Block_copy(block);
    } 
  return self;
}

@end

/**
 * <p>
 *   This function is provided to let threads started by some other
 *   software library register themselves to be used with the
 *   GNUstep system.  All such threads should call this function
 *   before attempting to use any GNUstep objects.
 * </p>
 * <p>
 *   Returns <code>YES</code> if the thread can be registered,
 *   <code>NO</code> if it is already registered.
 * </p>
 * <p>
 *   Sends out a <code>NSWillBecomeMultiThreadedNotification</code>
 *   if the process was not already multithreaded.
 * </p>
 */
BOOL
GSRegisterCurrentThread(void)
{
  return [NSThread _createThreadForCurrentPthread];
}

/**
 * <p>
 *   This function is provided to let threads started by some other
 *   software library unregister themselves from the GNUstep threading
 *   system.
 * </p>
 * <p>
 *   Calling this function causes a
 *   <code>NSThreadWillExitNotification</code>
 *   to be sent out, and destroys the GNUstep NSThread object
 *   associated with the thread (like [NSThread+exit]) but does
 *   not exit the underlying thread.
 * </p>
 */
void
GSUnregisterCurrentThread(void)
{
  unregisterActiveThread(GSCurrentThread());
}