/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*- */

/* This Source Code Form is subject to the terms of the Mozilla Public

 * License, v. 2.0. If a copy of the MPL was not distributed with this

 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#include "primpl.h"

#include <string.h>

#if defined(HPUX) && defined(_PR_PTHREADS)

#  include <pthread.h>

#  define HAVE_UNIX98_RWLOCK

#  define RWLOCK_T pthread_rwlock_t

#  define RWLOCK_INIT(lock) pthread_rwlock_init(lock, NULL)

#  define RWLOCK_DESTROY(lock) pthread_rwlock_destroy(lock)

#  define RWLOCK_RDLOCK(lock) pthread_rwlock_rdlock(lock)

#  define RWLOCK_WRLOCK(lock) pthread_rwlock_wrlock(lock)

#  define RWLOCK_UNLOCK(lock) pthread_rwlock_unlock(lock)

#elif defined(SOLARIS) && \

    (defined(_PR_PTHREADS) || defined(_PR_GLOBAL_THREADS_ONLY))

#  include <synch.h>

#  define HAVE_UI_RWLOCK

#  define RWLOCK_T rwlock_t

#  define RWLOCK_INIT(lock) rwlock_init(lock, USYNC_THREAD, NULL)

#  define RWLOCK_DESTROY(lock) rwlock_destroy(lock)

#  define RWLOCK_RDLOCK(lock) rw_rdlock(lock)

#  define RWLOCK_WRLOCK(lock) rw_wrlock(lock)

#  define RWLOCK_UNLOCK(lock) rw_unlock(lock)

#endif

/*

 * Reader-writer lock

 */

struct PRRWLock {

  char* rw_name;    /* lock name                    */

  PRUint32 rw_rank; /* rank of the lock             */

#if defined(HAVE_UNIX98_RWLOCK) || defined(HAVE_UI_RWLOCK)

  RWLOCK_T rw_lock;

#else

  PRLock* rw_lock;

  PRInt32 rw_lock_cnt; /* ==  0, if unlocked           */

  /* == -1, if write-locked       */

  /* > 0  , # of read locks       */

  PRUint32 rw_reader_cnt;     /* number of waiting readers    */

  PRUint32 rw_writer_cnt;     /* number of waiting writers    */

  PRCondVar* rw_reader_waitq; /* cvar for readers             */

  PRCondVar* rw_writer_waitq; /* cvar for writers             */

#  ifdef DEBUG

  PRThread* rw_owner; /* lock owner for write-lock    */

#  endif

#endif

};

#ifdef DEBUG

#  define _PR_RWLOCK_RANK_ORDER_DEBUG /* enable deadlock detection using \

                                         rank-order for locks            \

                                      */

#endif

#ifdef _PR_RWLOCK_RANK_ORDER_DEBUG

static PRUintn pr_thread_rwlock_key; /* TPD key for lock stack */

static PRUintn pr_thread_rwlock_alloc_failed;

#  define _PR_RWLOCK_RANK_ORDER_LIMIT 10

typedef struct thread_rwlock_stack {

  PRInt32 trs_index;                                /* top of stack */

  PRRWLock* trs_stack[_PR_RWLOCK_RANK_ORDER_LIMIT]; /* stack of lock

                                                       pointers */

} thread_rwlock_stack;

static void _PR_SET_THREAD_RWLOCK_RANK(PRRWLock* rwlock);

static PRUint32 _PR_GET_THREAD_RWLOCK_RANK(void);

static void _PR_UNSET_THREAD_RWLOCK_RANK(PRRWLock* rwlock);

static void _PR_RELEASE_LOCK_STACK(void* lock_stack);

#endif

/*

 * Reader/Writer Locks

 */

/*

 * PR_NewRWLock

 *      Create a reader-writer lock, with the given lock rank and lock name

 *

 */

PR_IMPLEMENT(PRRWLock*)

PR_NewRWLock(PRUint32 lock_rank, const char* lock_name) {

  PRRWLock* rwlock;

#if defined(HAVE_UNIX98_RWLOCK) || defined(HAVE_UI_RWLOCK)

  int err;

#endif

  if (!_pr_initialized) {

    _PR_ImplicitInitialization();

  }

  rwlock = PR_NEWZAP(PRRWLock);

  if (rwlock == NULL) {

    return NULL;

  }

  rwlock->rw_rank = lock_rank;

  if (lock_name != NULL) {

    rwlock->rw_name = (char*)PR_Malloc(strlen(lock_name) + 1);

    if (rwlock->rw_name == NULL) {

      PR_DELETE(rwlock);

      return (NULL);

    }

    strcpy(rwlock->rw_name, lock_name);

  } else {

    rwlock->rw_name = NULL;

  }

#if defined(HAVE_UNIX98_RWLOCK) || defined(HAVE_UI_RWLOCK)

  err = RWLOCK_INIT(&rwlock->rw_lock);

  if (err != 0) {

    PR_SetError(PR_UNKNOWN_ERROR, err);

    PR_Free(rwlock->rw_name);

    PR_DELETE(rwlock);

    return NULL;

  }

  return rwlock;

#else

  rwlock->rw_lock = PR_NewLock();

  if (rwlock->rw_lock == NULL) {

    goto failed;

  }

  rwlock->rw_reader_waitq = PR_NewCondVar(rwlock->rw_lock);

  if (rwlock->rw_reader_waitq == NULL) {

    goto failed;

  }

  rwlock->rw_writer_waitq = PR_NewCondVar(rwlock->rw_lock);

  if (rwlock->rw_writer_waitq == NULL) {

    goto failed;

  }

  rwlock->rw_reader_cnt = 0;

  rwlock->rw_writer_cnt = 0;

  rwlock->rw_lock_cnt = 0;

  return rwlock;

failed:

  if (rwlock->rw_reader_waitq != NULL) {

    PR_DestroyCondVar(rwlock->rw_reader_waitq);

  }

  if (rwlock->rw_lock != NULL) {

    PR_DestroyLock(rwlock->rw_lock);

  }

  PR_Free(rwlock->rw_name);

  PR_DELETE(rwlock);

  return NULL;

#endif

}

/*

** Destroy the given RWLock "lock".

*/

PR_IMPLEMENT(void)

PR_DestroyRWLock(PRRWLock* rwlock) {

#if defined(HAVE_UNIX98_RWLOCK) || defined(HAVE_UI_RWLOCK)

  int err;

  err = RWLOCK_DESTROY(&rwlock->rw_lock);

  PR_ASSERT(err == 0);

#else

  PR_ASSERT(rwlock->rw_reader_cnt == 0);

  PR_DestroyCondVar(rwlock->rw_reader_waitq);

  PR_DestroyCondVar(rwlock->rw_writer_waitq);

  PR_DestroyLock(rwlock->rw_lock);

#endif

  if (rwlock->rw_name != NULL) {

    PR_Free(rwlock->rw_name);

  }

  PR_DELETE(rwlock);

}

/*

** Read-lock the RWLock.

*/

PR_IMPLEMENT(void)

PR_RWLock_Rlock(PRRWLock* rwlock) {

#if defined(HAVE_UNIX98_RWLOCK) || defined(HAVE_UI_RWLOCK)

  int err;

#endif

#ifdef _PR_RWLOCK_RANK_ORDER_DEBUG

  /*

   * assert that rank ordering is not violated; the rank of 'rwlock' should

   * be equal to or greater than the highest rank of all the locks held by

   * the thread.

   */

  PR_ASSERT((rwlock->rw_rank == PR_RWLOCK_RANK_NONE) ||

            (rwlock->rw_rank >= _PR_GET_THREAD_RWLOCK_RANK()));

#endif

#if defined(HAVE_UNIX98_RWLOCK) || defined(HAVE_UI_RWLOCK)

  err = RWLOCK_RDLOCK(&rwlock->rw_lock);

  PR_ASSERT(err == 0);

#else

  PR_Lock(rwlock->rw_lock);

  /*

   * wait if write-locked or if a writer is waiting; preference for writers

   */

  while ((rwlock->rw_lock_cnt < 0) || (rwlock->rw_writer_cnt > 0)) {

    rwlock->rw_reader_cnt++;

    PR_WaitCondVar(rwlock->rw_reader_waitq, PR_INTERVAL_NO_TIMEOUT);

    rwlock->rw_reader_cnt--;

  }

  /*

   * Increment read-lock count

   */

  rwlock->rw_lock_cnt++;

  PR_Unlock(rwlock->rw_lock);

#endif

#ifdef _PR_RWLOCK_RANK_ORDER_DEBUG

  /*

   * update thread's lock rank

   */

  if (rwlock->rw_rank != PR_RWLOCK_RANK_NONE) {

    _PR_SET_THREAD_RWLOCK_RANK(rwlock);

  }

#endif

}

/*

** Write-lock the RWLock.

*/

PR_IMPLEMENT(void)

PR_RWLock_Wlock(PRRWLock* rwlock) {

#if defined(DEBUG)

  PRThread* me = PR_GetCurrentThread();

#endif

#if defined(HAVE_UNIX98_RWLOCK) || defined(HAVE_UI_RWLOCK)

  int err;

#endif

#ifdef _PR_RWLOCK_RANK_ORDER_DEBUG

  /*

   * assert that rank ordering is not violated; the rank of 'rwlock' should

   * be equal to or greater than the highest rank of all the locks held by

   * the thread.

   */

  PR_ASSERT((rwlock->rw_rank == PR_RWLOCK_RANK_NONE) ||

            (rwlock->rw_rank >= _PR_GET_THREAD_RWLOCK_RANK()));

#endif

#if defined(HAVE_UNIX98_RWLOCK) || defined(HAVE_UI_RWLOCK)

  err = RWLOCK_WRLOCK(&rwlock->rw_lock);

  PR_ASSERT(err == 0);

#else

  PR_Lock(rwlock->rw_lock);

  /*

   * wait if read locked

   */

  while (rwlock->rw_lock_cnt != 0) {

    rwlock->rw_writer_cnt++;

    PR_WaitCondVar(rwlock->rw_writer_waitq, PR_INTERVAL_NO_TIMEOUT);

    rwlock->rw_writer_cnt--;

  }

  /*

   * apply write lock

   */

  rwlock->rw_lock_cnt--;

  PR_ASSERT(rwlock->rw_lock_cnt == -1);

#  ifdef DEBUG

  PR_ASSERT(me != NULL);

  rwlock->rw_owner = me;

#  endif

  PR_Unlock(rwlock->rw_lock);

#endif

#ifdef _PR_RWLOCK_RANK_ORDER_DEBUG

  /*

   * update thread's lock rank

   */

  if (rwlock->rw_rank != PR_RWLOCK_RANK_NONE) {

    _PR_SET_THREAD_RWLOCK_RANK(rwlock);

  }

#endif

}

/*

** Unlock the RW lock.

*/

PR_IMPLEMENT(void)

PR_RWLock_Unlock(PRRWLock* rwlock) {

#if defined(DEBUG)

  PRThread* me = PR_GetCurrentThread();

#endif

#if defined(HAVE_UNIX98_RWLOCK) || defined(HAVE_UI_RWLOCK)

  int err;

#endif

#if defined(HAVE_UNIX98_RWLOCK) || defined(HAVE_UI_RWLOCK)

  err = RWLOCK_UNLOCK(&rwlock->rw_lock);

  PR_ASSERT(err == 0);

#else

  PR_Lock(rwlock->rw_lock);

  /*

   * lock must be read or write-locked

   */

  PR_ASSERT(rwlock->rw_lock_cnt != 0);

  if (rwlock->rw_lock_cnt > 0) {

    /*

     * decrement read-lock count

     */

    rwlock->rw_lock_cnt--;

    if (rwlock->rw_lock_cnt == 0) {

      /*

       * lock is not read-locked anymore; wakeup a waiting writer

       */

      if (rwlock->rw_writer_cnt > 0) {

        PR_NotifyCondVar(rwlock->rw_writer_waitq);

      }

    }

  } else {

    PR_ASSERT(rwlock->rw_lock_cnt == -1);

    rwlock->rw_lock_cnt = 0;

#  ifdef DEBUG

    PR_ASSERT(rwlock->rw_owner == me);

    rwlock->rw_owner = NULL;

#  endif

    /*

     * wakeup a writer, if present; preference for writers

     */

    if (rwlock->rw_writer_cnt > 0) {

      PR_NotifyCondVar(rwlock->rw_writer_waitq);

    }

    /*

     * else, wakeup all readers, if any

     */

    else if (rwlock->rw_reader_cnt > 0) {

      PR_NotifyAllCondVar(rwlock->rw_reader_waitq);

    }

  }

  PR_Unlock(rwlock->rw_lock);

#endif

#ifdef _PR_RWLOCK_RANK_ORDER_DEBUG

  /*

   * update thread's lock rank

   */

  if (rwlock->rw_rank != PR_RWLOCK_RANK_NONE) {

    _PR_UNSET_THREAD_RWLOCK_RANK(rwlock);

  }

#endif

  return;

}

#ifndef _PR_RWLOCK_RANK_ORDER_DEBUG

void _PR_InitRWLocks(void) {}

#else

void _PR_InitRWLocks(void) {

  /*

   * allocated thread-private-data index for rwlock list

   */

  if (PR_NewThreadPrivateIndex(&pr_thread_rwlock_key, _PR_RELEASE_LOCK_STACK) ==

      PR_FAILURE) {

    pr_thread_rwlock_alloc_failed = 1;

    return;

  }

}

/*

 * _PR_SET_THREAD_RWLOCK_RANK

 *      Set a thread's lock rank, which is the highest of the ranks of all

 *      the locks held by the thread. Pointers to the locks are added to a

 *      per-thread list, which is anchored off a thread-private data key.

 */

static void _PR_SET_THREAD_RWLOCK_RANK(PRRWLock* rwlock) {

  thread_rwlock_stack* lock_stack;

  PRStatus rv;

  /*

   * allocate a lock stack

   */

  if ((lock_stack = PR_GetThreadPrivate(pr_thread_rwlock_key)) == NULL) {

    lock_stack =

        (thread_rwlock_stack*)PR_CALLOC(1 * sizeof(thread_rwlock_stack));

    if (lock_stack) {

      rv = PR_SetThreadPrivate(pr_thread_rwlock_key, lock_stack);

      if (rv == PR_FAILURE) {

        PR_DELETE(lock_stack);

        pr_thread_rwlock_alloc_failed = 1;

        return;

      }

    } else {

      pr_thread_rwlock_alloc_failed = 1;

      return;

    }

  }

  /*

   * add rwlock to lock stack, if limit is not exceeded

   */

  if (lock_stack) {

    if (lock_stack->trs_index < _PR_RWLOCK_RANK_ORDER_LIMIT) {

      lock_stack->trs_stack[lock_stack->trs_index++] = rwlock;

    }

  }

}

static void _PR_RELEASE_LOCK_STACK(void* lock_stack) {

  PR_ASSERT(lock_stack);

  PR_DELETE(lock_stack);

}

/*

 * _PR_GET_THREAD_RWLOCK_RANK

 *

 *      return thread's lock rank. If thread-private-data for the lock

 *      stack is not allocated, return PR_RWLOCK_RANK_NONE.

 */

static PRUint32 _PR_GET_THREAD_RWLOCK_RANK(void) {

  thread_rwlock_stack* lock_stack;

  lock_stack = PR_GetThreadPrivate(pr_thread_rwlock_key);

  if (lock_stack == NULL || lock_stack->trs_index == 0) {

    return (PR_RWLOCK_RANK_NONE);

  } else {

    return (lock_stack->trs_stack[lock_stack->trs_index - 1]->rw_rank);

  }

}

/*

 * _PR_UNSET_THREAD_RWLOCK_RANK

 *

 *      remove the rwlock from the lock stack. Since locks may not be

 *      unlocked in a FIFO order, the entire lock stack is searched.

 */

static void _PR_UNSET_THREAD_RWLOCK_RANK(PRRWLock* rwlock) {

  thread_rwlock_stack* lock_stack;

  int new_index = 0, index, done = 0;

  lock_stack = PR_GetThreadPrivate(pr_thread_rwlock_key);

  PR_ASSERT(lock_stack != NULL);

  for (index = lock_stack->trs_index - 1; index >= 0; index--) {

    if (!done && (lock_stack->trs_stack[index] == rwlock)) {

      /*

       * reset the slot for rwlock

       */

      lock_stack->trs_stack[index] = NULL;

      done = 1;

    }

    /*

     * search for the lowest-numbered empty slot, above which there are

     * no non-empty slots

     */

    if (!new_index && (lock_stack->trs_stack[index] != NULL)) {

      new_index = index + 1;

    }

    if (done && new_index) {

      break;

    }

  }

  /*

   * set top of stack to highest numbered empty slot

   */

  lock_stack->trs_index = new_index;

}

#endif /* _PR_RWLOCK_RANK_ORDER_DEBUG */