/* Locking in multithreaded situations.

   Copyright (C) 2005-2018 Free Software Foundation, Inc.

   This program is free software; you can redistribute it and/or modify

   it under the terms of the GNU General Public License as published by

   the Free Software Foundation; either version 3, or (at your option)

   any later version.

   This program 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 General Public License for more details.

   You should have received a copy of the GNU General Public License

   along with this program; if not, see <https://www.gnu.org/licenses/>.  */

/* Written by Bruno Haible <bruno@clisp.org>, 2005.

   Based on GCC's gthr-posix.h, gthr-posix95.h, gthr-solaris.h,

   gthr-win32.h.  */

#include <config.h>

#include "glthread/lock.h"

/* ========================================================================= */

#if USE_POSIX_THREADS

/* -------------------------- gl_lock_t datatype -------------------------- */

/* ------------------------- gl_rwlock_t datatype ------------------------- */

# if HAVE_PTHREAD_RWLOCK && (HAVE_PTHREAD_RWLOCK_RDLOCK_PREFER_WRITER || (defined PTHREAD_RWLOCK_WRITER_NONRECURSIVE_INITIALIZER_NP && (__GNU_LIBRARY__ > 1)))

#  ifdef PTHREAD_RWLOCK_INITIALIZER

#   if !HAVE_PTHREAD_RWLOCK_RDLOCK_PREFER_WRITER

     /* glibc with bug https://sourceware.org/bugzilla/show_bug.cgi?id=13701 */

int

glthread_rwlock_init_for_glibc (pthread_rwlock_t *lock)

{

  pthread_rwlockattr_t attributes;

  int err;

  err = pthread_rwlockattr_init (&attributes);

  if (err != 0)

    return err;

  /* Note: PTHREAD_RWLOCK_PREFER_WRITER_NONRECURSIVE_NP is the only value that

     causes the writer to be preferred. PTHREAD_RWLOCK_PREFER_WRITER_NP does not

     do this; see

     http://man7.org/linux/man-pages/man3/pthread_rwlockattr_setkind_np.3.html */

  err = pthread_rwlockattr_setkind_np (&attributes,

                                       PTHREAD_RWLOCK_PREFER_WRITER_NONRECURSIVE_NP);

  if (err == 0)

    err = pthread_rwlock_init(lock, &attributes);

  /* pthread_rwlockattr_destroy always returns 0.  It cannot influence the

     return value.  */

  pthread_rwlockattr_destroy (&attributes);

  return err;

}

#   endif

#  else

int

glthread_rwlock_init_multithreaded (gl_rwlock_t *lock)

{

  int err;

  err = pthread_rwlock_init (&lock->rwlock, NULL);

  if (err != 0)

    return err;

  lock->initialized = 1;

  return 0;

}

int

glthread_rwlock_rdlock_multithreaded (gl_rwlock_t *lock)

{

  if (!lock->initialized)

    {

      int err;

      err = pthread_mutex_lock (&lock->guard);

      if (err != 0)

        return err;

      if (!lock->initialized)

        {

          err = glthread_rwlock_init_multithreaded (lock);

          if (err != 0)

            {

              pthread_mutex_unlock (&lock->guard);

              return err;

            }

        }

      err = pthread_mutex_unlock (&lock->guard);

      if (err != 0)

        return err;

    }

  return pthread_rwlock_rdlock (&lock->rwlock);

}

int

glthread_rwlock_wrlock_multithreaded (gl_rwlock_t *lock)

{

  if (!lock->initialized)

    {

      int err;

      err = pthread_mutex_lock (&lock->guard);

      if (err != 0)

        return err;

      if (!lock->initialized)

        {

          err = glthread_rwlock_init_multithreaded (lock);

          if (err != 0)

            {

              pthread_mutex_unlock (&lock->guard);

              return err;

            }

        }

      err = pthread_mutex_unlock (&lock->guard);

      if (err != 0)

        return err;

    }

  return pthread_rwlock_wrlock (&lock->rwlock);

}

int

glthread_rwlock_unlock_multithreaded (gl_rwlock_t *lock)

{

  if (!lock->initialized)

    return EINVAL;

  return pthread_rwlock_unlock (&lock->rwlock);

}

int

glthread_rwlock_destroy_multithreaded (gl_rwlock_t *lock)

{

  int err;

  if (!lock->initialized)

    return EINVAL;

  err = pthread_rwlock_destroy (&lock->rwlock);

  if (err != 0)

    return err;

  lock->initialized = 0;

  return 0;

}

#  endif

# else

int

glthread_rwlock_init_multithreaded (gl_rwlock_t *lock)

{

  int err;

  err = pthread_mutex_init (&lock->lock, NULL);

  if (err != 0)

    return err;

  err = pthread_cond_init (&lock->waiting_readers, NULL);

  if (err != 0)

    return err;

  err = pthread_cond_init (&lock->waiting_writers, NULL);

  if (err != 0)

    return err;

  lock->waiting_writers_count = 0;

  lock->runcount = 0;

  return 0;

}

int

glthread_rwlock_rdlock_multithreaded (gl_rwlock_t *lock)

{

  int err;

  err = pthread_mutex_lock (&lock->lock);

  if (err != 0)

    return err;

  /* Test whether only readers are currently running, and whether the runcount

     field will not overflow, and whether no writer is waiting.  The latter

     condition is because POSIX recommends that "write locks shall take

     precedence over read locks", to avoid "writer starvation".  */

  while (!(lock->runcount + 1 > 0 && lock->waiting_writers_count == 0))

    {

      /* This thread has to wait for a while.  Enqueue it among the

         waiting_readers.  */

      err = pthread_cond_wait (&lock->waiting_readers, &lock->lock);

      if (err != 0)

        {

          pthread_mutex_unlock (&lock->lock);

          return err;

        }

    }

  lock->runcount++;

  return pthread_mutex_unlock (&lock->lock);

}

int

glthread_rwlock_wrlock_multithreaded (gl_rwlock_t *lock)

{

  int err;

  err = pthread_mutex_lock (&lock->lock);

  if (err != 0)

    return err;

  /* Test whether no readers or writers are currently running.  */

  while (!(lock->runcount == 0))

    {

      /* This thread has to wait for a while.  Enqueue it among the

         waiting_writers.  */

      lock->waiting_writers_count++;

      err = pthread_cond_wait (&lock->waiting_writers, &lock->lock);

      if (err != 0)

        {

          lock->waiting_writers_count--;

          pthread_mutex_unlock (&lock->lock);

          return err;

        }

      lock->waiting_writers_count--;

    }

  lock->runcount--; /* runcount becomes -1 */

  return pthread_mutex_unlock (&lock->lock);

}

int

glthread_rwlock_unlock_multithreaded (gl_rwlock_t *lock)

{

  int err;

  err = pthread_mutex_lock (&lock->lock);

  if (err != 0)

    return err;

  if (lock->runcount < 0)

    {

      /* Drop a writer lock.  */

      if (!(lock->runcount == -1))

        {

          pthread_mutex_unlock (&lock->lock);

          return EINVAL;

        }

      lock->runcount = 0;

    }

  else

    {

      /* Drop a reader lock.  */

      if (!(lock->runcount > 0))

        {

          pthread_mutex_unlock (&lock->lock);

          return EINVAL;

        }

      lock->runcount--;

    }

  if (lock->runcount == 0)

    {

      /* POSIX recommends that "write locks shall take precedence over read

         locks", to avoid "writer starvation".  */

      if (lock->waiting_writers_count > 0)

        {

          /* Wake up one of the waiting writers.  */

          err = pthread_cond_signal (&lock->waiting_writers);

          if (err != 0)

            {

              pthread_mutex_unlock (&lock->lock);

              return err;

            }

        }

      else

        {

          /* Wake up all waiting readers.  */

          err = pthread_cond_broadcast (&lock->waiting_readers);

          if (err != 0)

            {

              pthread_mutex_unlock (&lock->lock);

              return err;

            }

        }

    }

  return pthread_mutex_unlock (&lock->lock);

}

int

glthread_rwlock_destroy_multithreaded (gl_rwlock_t *lock)

{

  int err;

  err = pthread_mutex_destroy (&lock->lock);

  if (err != 0)

    return err;

  err = pthread_cond_destroy (&lock->waiting_readers);

  if (err != 0)

    return err;

  err = pthread_cond_destroy (&lock->waiting_writers);

  if (err != 0)

    return err;

  return 0;

}

# endif

/* --------------------- gl_recursive_lock_t datatype --------------------- */

# if HAVE_PTHREAD_MUTEX_RECURSIVE

#  if defined PTHREAD_RECURSIVE_MUTEX_INITIALIZER || defined PTHREAD_RECURSIVE_MUTEX_INITIALIZER_NP

int

glthread_recursive_lock_init_multithreaded (gl_recursive_lock_t *lock)

{

  pthread_mutexattr_t attributes;

  int err;

  err = pthread_mutexattr_init (&attributes);

  if (err != 0)

    return err;

  err = pthread_mutexattr_settype (&attributes, PTHREAD_MUTEX_RECURSIVE);

  if (err != 0)

    {

      pthread_mutexattr_destroy (&attributes);

      return err;

    }

  err = pthread_mutex_init (lock, &attributes);

  if (err != 0)

    {

      pthread_mutexattr_destroy (&attributes);

      return err;

    }

  err = pthread_mutexattr_destroy (&attributes);

  if (err != 0)

    return err;

  return 0;

}

#  else

int

glthread_recursive_lock_init_multithreaded (gl_recursive_lock_t *lock)

{

  pthread_mutexattr_t attributes;

  int err;

  err = pthread_mutexattr_init (&attributes);

  if (err != 0)

    return err;

  err = pthread_mutexattr_settype (&attributes, PTHREAD_MUTEX_RECURSIVE);

  if (err != 0)

    {

      pthread_mutexattr_destroy (&attributes);

      return err;

    }

  err = pthread_mutex_init (&lock->recmutex, &attributes);

  if (err != 0)

    {

      pthread_mutexattr_destroy (&attributes);

      return err;

    }

  err = pthread_mutexattr_destroy (&attributes);

  if (err != 0)

    return err;

  lock->initialized = 1;

  return 0;

}

int

glthread_recursive_lock_lock_multithreaded (gl_recursive_lock_t *lock)

{

  if (!lock->initialized)

    {

      int err;

      err = pthread_mutex_lock (&lock->guard);

      if (err != 0)

        return err;

      if (!lock->initialized)

        {

          err = glthread_recursive_lock_init_multithreaded (lock);

          if (err != 0)

            {

              pthread_mutex_unlock (&lock->guard);

              return err;

            }

        }

      err = pthread_mutex_unlock (&lock->guard);

      if (err != 0)

        return err;

    }

  return pthread_mutex_lock (&lock->recmutex);

}

int

glthread_recursive_lock_unlock_multithreaded (gl_recursive_lock_t *lock)

{

  if (!lock->initialized)

    return EINVAL;

  return pthread_mutex_unlock (&lock->recmutex);

}

int

glthread_recursive_lock_destroy_multithreaded (gl_recursive_lock_t *lock)

{

  int err;

  if (!lock->initialized)

    return EINVAL;

  err = pthread_mutex_destroy (&lock->recmutex);

  if (err != 0)

    return err;

  lock->initialized = 0;

  return 0;

}

#  endif

# else

int

glthread_recursive_lock_init_multithreaded (gl_recursive_lock_t *lock)

{

  int err;

  err = pthread_mutex_init (&lock->mutex, NULL);

  if (err != 0)

    return err;

  lock->owner = (pthread_t) 0;

  lock->depth = 0;

  return 0;

}

int

glthread_recursive_lock_lock_multithreaded (gl_recursive_lock_t *lock)

{

  pthread_t self = pthread_self ();

  if (lock->owner != self)

    {

      int err;

      err = pthread_mutex_lock (&lock->mutex);

      if (err != 0)

        return err;

      lock->owner = self;

    }

  if (++(lock->depth) == 0) /* wraparound? */

    {

      lock->depth--;

      return EAGAIN;

    }

  return 0;

}

int

glthread_recursive_lock_unlock_multithreaded (gl_recursive_lock_t *lock)

{

  if (lock->owner != pthread_self ())

    return EPERM;

  if (lock->depth == 0)

    return EINVAL;

  if (--(lock->depth) == 0)

    {

      lock->owner = (pthread_t) 0;

      return pthread_mutex_unlock (&lock->mutex);

    }

  else

    return 0;

}

int

glthread_recursive_lock_destroy_multithreaded (gl_recursive_lock_t *lock)

{

  if (lock->owner != (pthread_t) 0)

    return EBUSY;

  return pthread_mutex_destroy (&lock->mutex);

}

# endif

/* -------------------------- gl_once_t datatype -------------------------- */

static const pthread_once_t fresh_once = PTHREAD_ONCE_INIT;

int

glthread_once_singlethreaded (pthread_once_t *once_control)

{

  /* We don't know whether pthread_once_t is an integer type, a floating-point

     type, a pointer type, or a structure type.  */

  char *firstbyte = (char *)once_control;

  if (*firstbyte == *(const char *)&fresh_once)

    {

      /* First time use of once_control.  Invert the first byte.  */

      *firstbyte = ~ *(const char *)&fresh_once;

      return 1;

    }

  else

    return 0;

}

#endif

/* ========================================================================= */

#if USE_PTH_THREADS

/* Use the GNU Pth threads library.  */

/* -------------------------- gl_lock_t datatype -------------------------- */

/* ------------------------- gl_rwlock_t datatype ------------------------- */

# if !HAVE_PTH_RWLOCK_ACQUIRE_PREFER_WRITER

int

glthread_rwlock_init_multithreaded (gl_rwlock_t *lock)

{

  if (!pth_mutex_init (&lock->lock))

    return errno;

  if (!pth_cond_init (&lock->waiting_readers))

    return errno;

  if (!pth_cond_init (&lock->waiting_writers))

    return errno;

  lock->waiting_writers_count = 0;

  lock->runcount = 0;

  lock->initialized = 1;

  return 0;

}

int

glthread_rwlock_rdlock_multithreaded (gl_rwlock_t *lock)

{

  if (!lock->initialized)

    glthread_rwlock_init_multithreaded (lock);

  if (!pth_mutex_acquire (&lock->lock, 0, NULL))

    return errno;

  /* Test whether only readers are currently running, and whether the runcount

     field will not overflow, and whether no writer is waiting.  The latter

     condition is because POSIX recommends that "write locks shall take

     precedence over read locks", to avoid "writer starvation".  */

  while (!(lock->runcount + 1 > 0 && lock->waiting_writers_count == 0))

    {

      /* This thread has to wait for a while.  Enqueue it among the

         waiting_readers.  */

      if (!pth_cond_await (&lock->waiting_readers, &lock->lock, NULL))

        {

          int err = errno;

          pth_mutex_release (&lock->lock);

          return err;

        }

    }

  lock->runcount++;

  return (!pth_mutex_release (&lock->lock) ? errno : 0);

}

int

glthread_rwlock_wrlock_multithreaded (gl_rwlock_t *lock)

{

  if (!lock->initialized)

    glthread_rwlock_init_multithreaded (lock);

  if (!pth_mutex_acquire (&lock->lock, 0, NULL))

    return errno;

  /* Test whether no readers or writers are currently running.  */

  while (!(lock->runcount == 0))

    {

      /* This thread has to wait for a while.  Enqueue it among the

         waiting_writers.  */

      lock->waiting_writers_count++;

      if (!pth_cond_await (&lock->waiting_writers, &lock->lock, NULL))

        {

          int err = errno;

          lock->waiting_writers_count--;

          pth_mutex_release (&lock->lock);

          return err;

        }

      lock->waiting_writers_count--;

    }

  lock->runcount--; /* runcount becomes -1 */

  return (!pth_mutex_release (&lock->lock) ? errno : 0);

}

int

glthread_rwlock_unlock_multithreaded (gl_rwlock_t *lock)

{

  int err;

  if (!lock->initialized)

    return EINVAL;

  if (!pth_mutex_acquire (&lock->lock, 0, NULL))

    return errno;

  if (lock->runcount < 0)

    {

      /* Drop a writer lock.  */

      if (!(lock->runcount == -1))

        {

          pth_mutex_release (&lock->lock);

          return EINVAL;

        }

      lock->runcount = 0;

    }

  else

    {

      /* Drop a reader lock.  */

      if (!(lock->runcount > 0))

        {

          pth_mutex_release (&lock->lock);

          return EINVAL;

        }

      lock->runcount--;

    }

  if (lock->runcount == 0)

    {

      /* POSIX recommends that "write locks shall take precedence over read

         locks", to avoid "writer starvation".  */

      if (lock->waiting_writers_count > 0)

        {

          /* Wake up one of the waiting writers.  */

          if (!pth_cond_notify (&lock->waiting_writers, FALSE))

            {

              int err = errno;

              pth_mutex_release (&lock->lock);

              return err;

            }

        }

      else

        {

          /* Wake up all waiting readers.  */

          if (!pth_cond_notify (&lock->waiting_readers, TRUE))

            {

              int err = errno;

              pth_mutex_release (&lock->lock);

              return err;

            }

        }

    }

  return (!pth_mutex_release (&lock->lock) ? errno : 0);

}

int

glthread_rwlock_destroy_multithreaded (gl_rwlock_t *lock)

{

  lock->initialized = 0;

  return 0;

}

# endif

/* --------------------- gl_recursive_lock_t datatype --------------------- */

/* -------------------------- gl_once_t datatype -------------------------- */

static void

glthread_once_call (void *arg)

{

  void (**gl_once_temp_addr) (void) = (void (**) (void)) arg;

  void (*initfunction) (void) = *gl_once_temp_addr;

  initfunction ();

}

int

glthread_once_multithreaded (pth_once_t *once_control, void (*initfunction) (void))

{

  void (*temp) (void) = initfunction;

  return (!pth_once (once_control, glthread_once_call, &temp) ? errno : 0);

}

int

glthread_once_singlethreaded (pth_once_t *once_control)

{

  /* We know that pth_once_t is an integer type.  */

  if (*once_control == PTH_ONCE_INIT)

    {

      /* First time use of once_control.  Invert the marker.  */

      *once_control = ~ PTH_ONCE_INIT;

      return 1;

    }

  else

    return 0;

}

#endif

/* ========================================================================= */

#if USE_SOLARIS_THREADS

/* Use the old Solaris threads library.  */

/* -------------------------- gl_lock_t datatype -------------------------- */

/* ------------------------- gl_rwlock_t datatype ------------------------- */

/* --------------------- gl_recursive_lock_t datatype --------------------- */

int

glthread_recursive_lock_init_multithreaded (gl_recursive_lock_t *lock)

{

  int err;

  err = mutex_init (&lock->mutex, USYNC_THREAD, NULL);

  if (err != 0)

    return err;

  lock->owner = (thread_t) 0;

  lock->depth = 0;

  return 0;

}

int

glthread_recursive_lock_lock_multithreaded (gl_recursive_lock_t *lock)

{

  thread_t self = thr_self ();

  if (lock->owner != self)

    {

      int err;

      err = mutex_lock (&lock->mutex);

      if (err != 0)

        return err;

      lock->owner = self;

    }

  if (++(lock->depth) == 0) /* wraparound? */

    {

      lock->depth--;

      return EAGAIN;

    }

  return 0;

}

int

glthread_recursive_lock_unlock_multithreaded (gl_recursive_lock_t *lock)

{

  if (lock->owner != thr_self ())

    return EPERM;

  if (lock->depth == 0)

    return EINVAL;

  if (--(lock->depth) == 0)

    {

      lock->owner = (thread_t) 0;

      return mutex_unlock (&lock->mutex);

    }

  else

    return 0;

}

int

glthread_recursive_lock_destroy_multithreaded (gl_recursive_lock_t *lock)

{

  if (lock->owner != (thread_t) 0)

    return EBUSY;

  return mutex_destroy (&lock->mutex);

}

/* -------------------------- gl_once_t datatype -------------------------- */

int

glthread_once_multithreaded (gl_once_t *once_control, void (*initfunction) (void))

{

  if (!once_control->inited)

    {

      int err;

      /* Use the mutex to guarantee that if another thread is already calling

         the initfunction, this thread waits until it's finished.  */

      err = mutex_lock (&once_control->mutex);

      if (err != 0)

        return err;

      if (!once_control->inited)

        {

          once_control->inited = 1;

          initfunction ();

        }

      return mutex_unlock (&once_control->mutex);

    }

  else

    return 0;

}

int

glthread_once_singlethreaded (gl_once_t *once_control)

{

  /* We know that gl_once_t contains an integer type.  */

  if (!once_control->inited)

    {

      /* First time use of once_control.  Invert the marker.  */

      once_control->inited = ~ 0;

      return 1;

    }

  else

    return 0;

}

#endif

/* ========================================================================= */

#if USE_WINDOWS_THREADS

/* -------------------------- gl_lock_t datatype -------------------------- */

void

glthread_lock_init_func (gl_lock_t *lock)

{

  InitializeCriticalSection (&lock->lock);

  lock->guard.done = 1;

}

int

glthread_lock_lock_func (gl_lock_t *lock)

{

  if (!lock->guard.done)

    {

      if (InterlockedIncrement (&lock->guard.started) == 0)

        /* This thread is the first one to need this lock.  Initialize it.  */

        glthread_lock_init (lock);

      else

        /* Yield the CPU while waiting for another thread to finish

           initializing this lock.  */

        while (!lock->guard.done)

          Sleep (0);

    }

  EnterCriticalSection (&lock->lock);

  return 0;

}

int

glthread_lock_unlock_func (gl_lock_t *lock)

{

  if (!lock->guard.done)

    return EINVAL;

  LeaveCriticalSection (&lock->lock);

  return 0;

}

int

glthread_lock_destroy_func (gl_lock_t *lock)

{

  if (!lock->guard.done)

    return EINVAL;

  DeleteCriticalSection (&lock->lock);

  lock->guard.done = 0;

  return 0;

}

/* ------------------------- gl_rwlock_t datatype ------------------------- */

/* In this file, the waitqueues are implemented as circular arrays.  */

#define gl_waitqueue_t gl_carray_waitqueue_t

static void

gl_waitqueue_init (gl_waitqueue_t *wq)

{

  wq->array = NULL;

  wq->count = 0;

  wq->alloc = 0;

  wq->offset = 0;

}

/* Enqueues the current thread, represented by an event, in a wait queue.

   Returns INVALID_HANDLE_VALUE if an allocation failure occurs.  */

static HANDLE

gl_waitqueue_add (gl_waitqueue_t *wq)

{

  HANDLE event;

  unsigned int index;

  if (wq->count == wq->alloc)

    {

      unsigned int new_alloc = 2 * wq->alloc + 1;

      HANDLE *new_array =

        (HANDLE *) realloc (wq->array, new_alloc * sizeof (HANDLE));

      if (new_array == NULL)

        /* No more memory.  */

        return INVALID_HANDLE_VALUE;

      /* Now is a good opportunity to rotate the array so that its contents

         starts at offset 0.  */

      if (wq->offset > 0)

        {

          unsigned int old_count = wq->count;

          unsigned int old_alloc = wq->alloc;

          unsigned int old_offset = wq->offset;

          unsigned int i;

          if (old_offset + old_count > old_alloc)