/* Copyright (C) 2000-2008 MySQL AB, 2008 Sun Microsystems, 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; version 2 of the License.

   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, write to the Free Software
   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA */

/* This makes a wrapper for mutex handling to make it easier to debug mutex */

#include <my_global.h>
#if defined(TARGET_OS_LINUX) && !defined (__USE_UNIX98)
#define __USE_UNIX98			/* To get rw locks under Linux */
#endif
#if defined(THREAD) && defined(SAFE_MUTEX)
#undef SAFE_MUTEX			/* Avoid safe_mutex redefinitions */
#include "mysys_priv.h"
#include "my_static.h"
#include <m_string.h>
#include <hash.h>

#ifndef DO_NOT_REMOVE_THREAD_WRAPPERS
/* Remove wrappers */
#undef pthread_mutex_t
#undef pthread_mutex_init
#undef pthread_mutex_lock
#undef pthread_mutex_unlock
#undef pthread_mutex_destroy
#undef pthread_cond_wait
#undef pthread_cond_timedwait
#ifdef HAVE_NONPOSIX_PTHREAD_MUTEX_INIT
#define pthread_mutex_init(a,b) my_pthread_noposix_mutex_init((a),(b))
#endif
#endif /* DO_NOT_REMOVE_THREAD_WRAPPERS */

static pthread_mutex_t THR_LOCK_mutex;
static ulong safe_mutex_count= 0;		/* Number of mutexes created */
static ulong safe_mutex_id= 0;
my_bool safe_mutex_deadlock_detector= 1;        /* On by default */

#ifdef SAFE_MUTEX_DETECT_DESTROY
static struct st_safe_mutex_create_info_t *safe_mutex_create_root= NULL;
#endif

static my_bool add_used_to_locked_mutex(safe_mutex_t *used_mutex,
                                        safe_mutex_deadlock_t *locked_mutex);
static my_bool add_to_locked_mutex(safe_mutex_deadlock_t *locked_mutex,
                                   safe_mutex_t *current_mutex);
static my_bool remove_from_locked_mutex(safe_mutex_t *mp,
                                        safe_mutex_t *delete_mutex);
static my_bool remove_from_used_mutex(safe_mutex_deadlock_t *locked_mutex,
                                      safe_mutex_t *mutex);
static void print_deadlock_warning(safe_mutex_t *new_mutex,
                                   safe_mutex_t *conflicting_mutex);

void safe_mutex_global_init(void)
{
  pthread_mutex_init(&THR_LOCK_mutex,MY_MUTEX_INIT_FAST);
  safe_mutex_id= safe_mutex_count= 0;
  safe_mutex_deadlock_detector= 1;

#ifdef SAFE_MUTEX_DETECT_DESTROY
  safe_mutex_create_root= 0;
#endif
}

static inline void remove_from_active_list(safe_mutex_t *mp)
{
  if (!(mp->active_flags & (MYF_NO_DEADLOCK_DETECTION | MYF_TRY_LOCK)))
  {
    /* Remove mutex from active mutex linked list */
    if (mp->next)
      mp->next->prev= mp->prev;
    if (mp->prev)
      mp->prev->next= mp->next;
    else
      *my_thread_var_mutex_in_use()= mp->next;
  }
  mp->prev= mp->next= 0;
}


int safe_mutex_init(safe_mutex_t *mp,
		    const pthread_mutexattr_t *attr __attribute__((unused)),
                    const char *name,
                    myf my_flags,
		    const char *file,
		    uint line)
{
  DBUG_ENTER("safe_mutex_init");
  DBUG_PRINT("enter",("mutex: 0x%lx  name: %s", (ulong) mp, name));
  bzero((char*) mp,sizeof(*mp));
  pthread_mutex_init(&mp->global,MY_MUTEX_INIT_ERRCHK);
  pthread_mutex_init(&mp->mutex,attr);
  /* Mark that mutex is initialized */
  mp->file= file;
  mp->line= line;
  /* Skip the very common '&' prefix from the autogenerated name */
  mp->name= name[0] == '&' ? name + 1 : name;

  if (safe_mutex_deadlock_detector && !( my_flags & MYF_NO_DEADLOCK_DETECTION))
  {
    if (!my_multi_malloc(MY_FAE | MY_WME,
                         &mp->locked_mutex, sizeof(*mp->locked_mutex),
                         &mp->used_mutex, sizeof(*mp->used_mutex), NullS))
    {
      /* Disable deadlock handling for this mutex */
      my_flags|= MYF_NO_DEADLOCK_DETECTION;
    }
    else
    {
      pthread_mutex_lock(&THR_LOCK_mutex);
      mp->id= ++safe_mutex_id;
      pthread_mutex_unlock(&THR_LOCK_mutex);
      my_hash_init(mp->locked_mutex, &my_charset_bin,
                   1000,
                   offsetof(safe_mutex_deadlock_t, id),
                   sizeof(mp->id),
                   0, 0, HASH_UNIQUE);
      my_hash_init(mp->used_mutex, &my_charset_bin,
                   1000,
                   offsetof(safe_mutex_t, id),
                   sizeof(mp->id),
                   0, 0, HASH_UNIQUE);
    }
  }
  else
    my_flags|= MYF_NO_DEADLOCK_DETECTION;
  mp->create_flags= my_flags;

#ifdef SAFE_MUTEX_DETECT_DESTROY
  /*
    Monitor the freeing of mutexes.  This code depends on single thread init
    and destroy
  */
  if ((mp->info= (safe_mutex_info_t *) malloc(sizeof(safe_mutex_info_t))))
  {
    struct st_safe_mutex_info_t *info= mp->info;

    info->init_file= file;
    info->init_line= line;
    info->prev= NULL;
    info->next= NULL;

    pthread_mutex_lock(&THR_LOCK_mutex);
    if ((info->next= safe_mutex_create_root))
      safe_mutex_create_root->prev= info;
    safe_mutex_create_root= info;
    safe_mutex_count++;
    pthread_mutex_unlock(&THR_LOCK_mutex);
  }
#else
  thread_safe_increment(safe_mutex_count, &THR_LOCK_mutex);
#endif /* SAFE_MUTEX_DETECT_DESTROY */
  DBUG_RETURN(0);
}


int safe_mutex_lock(safe_mutex_t *mp, myf my_flags, const char *file,
                    uint line)
{
  int error;
  DBUG_PRINT("mutex", ("%s (0x%lx) locking", mp->name ? mp->name : "Null",
                       (ulong) mp));
  if (!mp->file)
  {
    fprintf(stderr,
	    "safe_mutex: Trying to lock unitialized mutex at %s, line %d\n",
	    file, line);
    fflush(stderr);
    abort();
  }

  pthread_mutex_lock(&mp->global);
  if (mp->count > 0)
  {
    /*
      Check that we are not trying to lock mutex twice. This is an error
      even if we are using 'try_lock' as it's not portably what happens
      if you lock the mutex many times and this is in any case bad
      behaviour that should not be encouraged
    */
    if (pthread_equal(pthread_self(),mp->thread))
    {
      fprintf(stderr,
              "safe_mutex: Trying to lock mutex at %s, line %d, when the"
              " mutex was already locked at %s, line %d in thread %s\n",
              file,line,mp->file, mp->line, my_thread_name());
      fflush(stderr);
      abort();
    }
  }
  pthread_mutex_unlock(&mp->global);

  /*
    If we are imitating trylock(), we need to take special
    precautions.

    - We cannot use pthread_mutex_lock() only since another thread can
      overtake this thread and take the lock before this thread
      causing pthread_mutex_trylock() to hang. In this case, we should
      just return EBUSY. Hence, we use pthread_mutex_trylock() to be
      able to return immediately.

    - We cannot just use trylock() and continue execution below, since
      this would generate an error and abort execution if the thread
      was overtaken and trylock() returned EBUSY . In this case, we
      instead just return EBUSY, since this is the expected behaviour
      of trylock().
   */
  if (my_flags & MYF_TRY_LOCK)
  {
    error= pthread_mutex_trylock(&mp->mutex);
    if (error == EBUSY)
      return error;
  }
  else
    error= pthread_mutex_lock(&mp->mutex);

  if (error || (error=pthread_mutex_lock(&mp->global)))
  {
    fprintf(stderr,"Got error %d when trying to lock mutex %s at %s, line %d\n",
	    error, mp->name, file, line);
    fflush(stderr);
    abort();
  }
  mp->thread= pthread_self();
  if (mp->count++)
  {
    fprintf(stderr,"safe_mutex: Error in thread libray: Got mutex %s at %s, "
            "line %d more than 1 time\n", mp->name, file,line);
    fflush(stderr);
    abort();
  }
  mp->file= file;
  mp->line= line;
  mp->active_flags= mp->create_flags | my_flags;
  pthread_mutex_unlock(&mp->global);

  /* Deadlock detection */

  mp->prev= mp->next= 0;
  if (!(mp->active_flags & (MYF_TRY_LOCK | MYF_NO_DEADLOCK_DETECTION)))
  {
    safe_mutex_t **mutex_in_use= my_thread_var_mutex_in_use();

    if (!mutex_in_use)
    {
      /* thread has not called my_thread_init() */
      mp->active_flags|= MYF_NO_DEADLOCK_DETECTION;
    }
    else
    {
      safe_mutex_t *mutex_root;
      if ((mutex_root= *mutex_in_use))   /* If not first locked */
      {
        /*
          Protect locked_mutex against changes if a mutex is deleted
        */
        pthread_mutex_lock(&THR_LOCK_mutex);

        if (! my_hash_search(mutex_root->locked_mutex, (uchar*) &mp->id, 0))
        {
          safe_mutex_deadlock_t *deadlock;
          safe_mutex_t *mutex;

          /* Create object to store mutex info */
          if (!(deadlock= my_malloc(sizeof(*deadlock),
                                    MYF(MY_ZEROFILL | MY_WME | MY_FAE))))
            goto abort_loop;
          deadlock->name= mp->name;
          deadlock->id= mp->id;
          deadlock->mutex= mp;
          /* The following is useful for debugging wrong mutex usage */
          deadlock->file= file;
          deadlock->line= line;

          /* Check if potential deadlock */
          mutex= mutex_root;
          do
          {
            if (my_hash_search(mp->locked_mutex, (uchar*) &mutex->id, 0))
            {
              print_deadlock_warning(mp, mutex);
              /* Mark wrong usage to avoid future warnings for same error */
              deadlock->warning_only= 1;
              add_to_locked_mutex(deadlock, mutex_root);
              DBUG_ASSERT(deadlock->count > 0);
              goto abort_loop;
            }
          }
          while ((mutex= mutex->next));

          /*
            Copy current mutex and all mutex that has been locked
            after current mutex (mp->locked_mutex) to all mutex that
            was locked before previous mutex (mutex_root->used_mutex)

            For example if A->B would have been done before and we
            are now locking (C) in B->C, then we would add C into
            B->locked_mutex and A->locked_mutex
          */
          my_hash_iterate(mutex_root->used_mutex,
                          (my_hash_walk_action) add_used_to_locked_mutex,
                          deadlock);

          /*
            Copy all current mutex and all mutex locked after current one
            into the prev mutex
          */
          add_used_to_locked_mutex(mutex_root, deadlock);
          DBUG_ASSERT(deadlock->count > 0);
        }
  abort_loop:
        pthread_mutex_unlock(&THR_LOCK_mutex);
      }
      /* Link mutex into mutex_in_use list */
      if ((mp->next= *mutex_in_use))
        (*mutex_in_use)->prev= mp;
      *mutex_in_use= mp;
    }
  }

  DBUG_PRINT("mutex", ("%s (0x%lx) locked", mp->name, (ulong) mp));
  return error;
}


int safe_mutex_unlock(safe_mutex_t *mp,const char *file, uint line)
{
  int error;
  DBUG_PRINT("mutex", ("%s (0x%lx) unlocking", mp->name, (ulong) mp));
  pthread_mutex_lock(&mp->global);
  if (mp->count == 0)
  {
    fprintf(stderr,
            "safe_mutex: Trying to unlock mutex %s that wasn't locked at "
            "%s, line %d\n"
            "Last used at %s, line: %d\n",
	    mp->name ? mp->name : "Null", file, line,
            mp->file ? mp->file : "Null", mp->line);
    fflush(stderr);
    abort();
  }
  if (!pthread_equal(pthread_self(),mp->thread))
  {
    fprintf(stderr,
            "safe_mutex: Trying to unlock mutex %s at %s, line %d that was "
            "locked by "
            "another thread at: %s, line: %d\n",
	    mp->name, file, line, mp->file, mp->line);
    fflush(stderr);
    abort();
  }
  mp->thread= 0;
  mp->count--;

  remove_from_active_list(mp);

#ifdef __WIN__
  pthread_mutex_unlock(&mp->mutex);
  error=0;
#else
  error=pthread_mutex_unlock(&mp->mutex);
  if (error)
  {
    fprintf(stderr,
            "safe_mutex: Got error: %d (%d) when trying to unlock mutex "
            "%s at %s, line %d\n", error, errno, mp->name, file, line);
    fflush(stderr);
    abort();
  }
#endif /* __WIN__ */
  pthread_mutex_unlock(&mp->global);
  return error;
}


int safe_cond_wait(pthread_cond_t *cond, safe_mutex_t *mp, const char *file,
		   uint line)
{
  int error;
  safe_mutex_t save_state;

  pthread_mutex_lock(&mp->global);
  if (mp->count == 0)
  {
    fprintf(stderr,
            "safe_mutex: Trying to cond_wait on a unlocked mutex %s at %s, "
            "line %d\n",
            mp->name ? mp->name : "Null", file, line);
    fflush(stderr);
    abort();
  }
  if (!pthread_equal(pthread_self(),mp->thread))
  {
    fprintf(stderr,
            "safe_mutex: Trying to cond_wait on a mutex %s at %s, line %d "
            "that was locked by another thread at: %s, line: %d\n",
	    mp->name, file, line, mp->file, mp->line);
    fflush(stderr);
    abort();
  }

  if (mp->count-- != 1)
  {
    fprintf(stderr,
            "safe_mutex:  Count was %d on locked mutex %s at %s, line %d\n",
	    mp->count+1, mp->name, file, line);
    fflush(stderr);
    abort();
  }
  save_state= *mp;
  remove_from_active_list(mp);
  pthread_mutex_unlock(&mp->global);
  error=pthread_cond_wait(cond,&mp->mutex);
  pthread_mutex_lock(&mp->global);

  if (error)
  {
    fprintf(stderr,
            "safe_mutex: Got error: %d (%d) when doing a safe_mutex_wait on "
            "%s at %s, line %d\n", error, errno, mp->name, file, line);
    fflush(stderr);
    abort();
  }
  /* Restore state as it was before */
  mp->thread=       save_state.thread;
  mp->active_flags= save_state.active_flags;
  mp->next=         save_state.next;
  mp->prev=         save_state.prev;

  if (mp->count++)
  {
    fprintf(stderr,
	    "safe_mutex:  Count was %d in thread 0x%lx when locking mutex %s "
            "at %s, line %d\n",
	    mp->count-1, my_thread_dbug_id(), mp->name, file, line);
    fflush(stderr);
    abort();
  }
  mp->file= file;
  mp->line=line;
  pthread_mutex_unlock(&mp->global);
  return error;
}


int safe_cond_timedwait(pthread_cond_t *cond, safe_mutex_t *mp,
			struct timespec *abstime,
			const char *file, uint line)
{
  int error;
  safe_mutex_t save_state;

  pthread_mutex_lock(&mp->global);
  if (mp->count != 1 || !pthread_equal(pthread_self(),mp->thread))
  {
    fprintf(stderr,
            "safe_mutex: Trying to cond_wait at %s, line %d on a not hold "
            "mutex %s\n",
            file, line, mp->name ? mp->name : "Null");
    fflush(stderr);
    abort();
  }
  mp->count--;					/* Mutex will be released */
  save_state= *mp;
  remove_from_active_list(mp);
  pthread_mutex_unlock(&mp->global);
  error=pthread_cond_timedwait(cond,&mp->mutex,abstime);
#ifdef EXTRA_DEBUG
  if (error && (error != EINTR && error != ETIMEDOUT && error != ETIME))
  {
    fprintf(stderr,
            "safe_mutex: Got error: %d (%d) when doing a safe_mutex_timedwait "
            "on %s at %s, line %d\n",
            error, errno, mp->name, file, line);
  }
#endif
  pthread_mutex_lock(&mp->global);
  /* Restore state as it was before */
  mp->thread=       save_state.thread;
  mp->active_flags= save_state.active_flags;
  mp->next=         save_state.next;
  mp->prev=         save_state.prev;

  if (mp->count++)
  {
    fprintf(stderr,
	    "safe_mutex:  Count was %d in thread 0x%lx when locking mutex "
            "%s at %s, line %d (error: %d (%d))\n",
	    mp->count-1, my_thread_dbug_id(), mp->name, file, line,
            error, error);
    fflush(stderr);
    abort();
  }
  mp->file= file;
  mp->line=line;
  pthread_mutex_unlock(&mp->global);
  return error;
}


int safe_mutex_destroy(safe_mutex_t *mp, const char *file, uint line)
{
  int error=0;
  DBUG_ENTER("safe_mutex_destroy");
  DBUG_PRINT("enter", ("mutex: 0x%lx  name: %s", (ulong) mp, mp->name));
  if (!mp->file)
  {
    fprintf(stderr,
	    "safe_mutex: Trying to destroy unitialized mutex at %s, line %d\n",
	    file, line);
    fflush(stderr);
    abort();
  }
  if (mp->count != 0)
  {
    fprintf(stderr,
            "safe_mutex: Trying to destroy a mutex %s that was locked at %s, "
            "line %d at %s, line %d\n",
	    mp->name, mp->file, mp->line, file, line);
    fflush(stderr);
    abort();
  }

  /* Free all entries that points to this one */
  safe_mutex_free_deadlock_data(mp);

#ifdef __WIN__ 
  pthread_mutex_destroy(&mp->global);
  pthread_mutex_destroy(&mp->mutex);
#else
  if (pthread_mutex_destroy(&mp->global))
    error=1;
  if (pthread_mutex_destroy(&mp->mutex))
    error=1;
#endif
  mp->file= 0;					/* Mark destroyed */

#ifdef SAFE_MUTEX_DETECT_DESTROY
  if (mp->info)
  {
    struct st_safe_mutex_info_t *info= mp->info;
    pthread_mutex_lock(&THR_LOCK_mutex);

    if (info->prev)
      info->prev->next = info->next;
    else
      safe_mutex_create_root = info->next;
    if (info->next)
      info->next->prev = info->prev;
    safe_mutex_count--;

    pthread_mutex_unlock(&THR_LOCK_mutex);
    free(info);
    mp->info= NULL;				/* Get crash if double free */
  }
#else
  thread_safe_sub(safe_mutex_count, 1, &THR_LOCK_mutex);
#endif /* SAFE_MUTEX_DETECT_DESTROY */
  DBUG_RETURN(error);
}


/**
  Free all data related to deadlock detection

  This is also useful together with safemalloc when you don't want to
  have reports of not freed memory for mysys mutexes.
*/

void safe_mutex_free_deadlock_data(safe_mutex_t *mp)
{
  /* Free all entries that points to this one */
  if (!(mp->create_flags & MYF_NO_DEADLOCK_DETECTION))
  {
    pthread_mutex_lock(&THR_LOCK_mutex);
    my_hash_iterate(mp->used_mutex,
                    (my_hash_walk_action) remove_from_locked_mutex,
                    mp);
    my_hash_iterate(mp->locked_mutex,
                    (my_hash_walk_action) remove_from_used_mutex,
                    mp);
    pthread_mutex_unlock(&THR_LOCK_mutex);

    my_hash_free(mp->used_mutex);
    my_hash_free(mp->locked_mutex);
    my_free(mp->locked_mutex, 0);
    mp->create_flags|= MYF_NO_DEADLOCK_DETECTION;
  }
}

/*
  Free global resources and check that all mutex has been destroyed

  SYNOPSIS
    safe_mutex_end()
    file		Print errors on this file

  NOTES
    We can't use DBUG_PRINT() here as we have in my_end() disabled
    DBUG handling before calling this function.

   In MySQL one may get one warning for a mutex created in my_thr_init.c
   This is ok, as this thread may not yet have been exited.
*/

void safe_mutex_end(FILE *file __attribute__((unused)))
{
  if (!safe_mutex_count)			/* safetly */
    pthread_mutex_destroy(&THR_LOCK_mutex);
#ifdef SAFE_MUTEX_DETECT_DESTROY
  if (!file)
    return;

  if (safe_mutex_count)
  {
    fprintf(file, "Warning: Not destroyed mutex: %lu\n", safe_mutex_count);
    (void) fflush(file);
  }
  {
    struct st_safe_mutex_info_t *ptr;
    for (ptr= safe_mutex_create_root ; ptr ; ptr= ptr->next)
    {
      fprintf(file, "\tMutex %s initiated at line %4u in '%s'\n",
	      ptr->name, ptr->init_line, ptr->init_file);
      (void) fflush(file);
    }
  }
#endif /* SAFE_MUTEX_DETECT_DESTROY */
}


static my_bool add_used_to_locked_mutex(safe_mutex_t *used_mutex,
                                        safe_mutex_deadlock_t *locked_mutex)
{
  /* Add mutex to all parent of the current mutex */
  if (!locked_mutex->warning_only)
  {
    (void) my_hash_iterate(locked_mutex->mutex->locked_mutex,
                           (my_hash_walk_action) add_to_locked_mutex,
                           used_mutex);
    /* mark that locked_mutex is locked after used_mutex */
    (void) add_to_locked_mutex(locked_mutex, used_mutex);
  }
  return 0;
}


/**
   register that locked_mutex was locked after current_mutex
*/

static my_bool add_to_locked_mutex(safe_mutex_deadlock_t *locked_mutex,
                                   safe_mutex_t *current_mutex)
{
  DBUG_ENTER("add_to_locked_mutex");
  DBUG_PRINT("info", ("inserting 0x%lx  into  0x%lx  (id: %lu -> %lu)",
                      (ulong) locked_mutex, (long) current_mutex,
                      locked_mutex->id, current_mutex->id));
  if (my_hash_insert(current_mutex->locked_mutex, (uchar*) locked_mutex))
  {
    /* Got mutex through two paths; ignore */
    DBUG_RETURN(0);
  }
  locked_mutex->count++;
  if (my_hash_insert(locked_mutex->mutex->used_mutex,
                     (uchar*) current_mutex))
  {
    DBUG_ASSERT(0);
  }
  DBUG_RETURN(0);
}


/**
  Remove mutex from the locked mutex hash
  @fn    remove_from_used_mutex()
  @param mp            Mutex that has delete_mutex in it's locked_mutex hash
  @param delete_mutex  Mutex should be removed from the hash

  @notes
    safe_mutex_deadlock_t entries in the locked hash are shared.
    When counter goes to 0, we delete the safe_mutex_deadlock_t entry.
*/

static my_bool remove_from_locked_mutex(safe_mutex_t *mp,
                                        safe_mutex_t *delete_mutex)
{
  safe_mutex_deadlock_t *found;
  DBUG_ENTER("remove_from_locked_mutex");
  DBUG_PRINT("enter", ("delete_mutex: 0x%lx  mutex: 0x%lx  (id: %lu <- %lu)",
                       (ulong) delete_mutex, (ulong) mp, 
                       delete_mutex->id, mp->id));

  found= (safe_mutex_deadlock_t*) my_hash_search(mp->locked_mutex,
                                                 (uchar*) &delete_mutex->id, 0);
  DBUG_ASSERT(found);
  if (found)
  {
    if (my_hash_delete(mp->locked_mutex, (uchar*) found))
    {
      DBUG_ASSERT(0);
    }
    if (!--found->count)
      my_free(found, MYF(0));
  }
  DBUG_RETURN(0);
}

static my_bool remove_from_used_mutex(safe_mutex_deadlock_t *locked_mutex,
                                      safe_mutex_t *mutex)
{
  DBUG_ENTER("remove_from_used_mutex");
  DBUG_PRINT("enter", ("delete_mutex: 0x%lx  mutex: 0x%lx  (id: %lu <- %lu)",
                       (ulong) mutex, (ulong) locked_mutex, 
                       mutex->id, locked_mutex->id));
  if (my_hash_delete(locked_mutex->mutex->used_mutex, (uchar*) mutex))
  {
    DBUG_ASSERT(0);
  }
  if (!--locked_mutex->count)
    my_free(locked_mutex, MYF(0));
  DBUG_RETURN(0);
}


static void print_deadlock_warning(safe_mutex_t *new_mutex,
                                   safe_mutex_t *parent_mutex)
{
  safe_mutex_t *mutex_root;
  DBUG_ENTER("print_deadlock_warning");
  DBUG_PRINT("enter", ("mutex: %s  parent: %s",
                       new_mutex->name, parent_mutex->name));

  fprintf(stderr, "safe_mutex: Found wrong usage of mutex "
          "'%s' and '%s'\n",
          parent_mutex->name, new_mutex->name);
  DBUG_PRINT("info", ("safe_mutex: Found wrong usage of mutex "
                      "'%s' and '%s'",
                      parent_mutex->name, new_mutex->name));
  fprintf(stderr, "Mutex currently locked (in reverse order):\n");
  DBUG_PRINT("info", ("Mutex currently locked (in reverse order):"));
  fprintf(stderr, "%-32.32s  %s  line %u\n", new_mutex->name, new_mutex->file,
          new_mutex->line);
  DBUG_PRINT("info", ("%-32.32s  %s  line %u\n", new_mutex->name,
                      new_mutex->file, new_mutex->line));
  for (mutex_root= *my_thread_var_mutex_in_use() ;
       mutex_root;
       mutex_root= mutex_root->next)
  {
    fprintf(stderr, "%-32.32s  %s  line %u\n", mutex_root->name,
            mutex_root->file, mutex_root->line);
    DBUG_PRINT("info", ("%-32.32s  %s  line %u", mutex_root->name,
                        mutex_root->file, mutex_root->line));
  }
  fflush(stderr);
  DBUG_VOID_RETURN;
}


#endif /* THREAD && SAFE_MUTEX */

#if defined(THREAD) && defined(MY_PTHREAD_FASTMUTEX) && !defined(SAFE_MUTEX)

#include "mysys_priv.h"
#include "my_static.h"
#include <m_string.h>

#include <m_ctype.h>
#include <hash.h>
#include <myisampack.h>
#include <mysys_err.h>
#include <my_sys.h>

#undef pthread_mutex_t
#undef pthread_mutex_init
#undef pthread_mutex_lock
#undef pthread_mutex_trylock
#undef pthread_mutex_unlock
#undef pthread_mutex_destroy
#undef pthread_cond_wait
#undef pthread_cond_timedwait

ulong mutex_delay(ulong delayloops)
{
  ulong	i;
  volatile ulong j;

  j = 0;

  for (i = 0; i < delayloops * 50; i++)
    j += i;

  return(j); 
}	

#define MY_PTHREAD_FASTMUTEX_SPINS 8
#define MY_PTHREAD_FASTMUTEX_DELAY 4

static int cpu_count= 0;

int my_pthread_fastmutex_init(my_pthread_fastmutex_t *mp,
                              const pthread_mutexattr_t *attr)
{
  if ((cpu_count > 1) && (attr == MY_MUTEX_INIT_FAST))
    mp->spins= MY_PTHREAD_FASTMUTEX_SPINS; 
  else
    mp->spins= 0;
  mp->rng_state= 1;
  return pthread_mutex_init(&mp->mutex, attr); 
}

/**
  Park-Miller random number generator. A simple linear congruential
  generator that operates in multiplicative group of integers modulo n.

  x_{k+1} = (x_k g) mod n

  Popular pair of parameters: n = 2^32 − 5 = 4294967291 and g = 279470273.
  The period of the generator is about 2^31.
  Largest value that can be returned: 2147483646 (RAND_MAX)

  Reference:

  S. K. Park and K. W. Miller
  "Random number generators: good ones are hard to find"
  Commun. ACM, October 1988, Volume 31, No 10, pages 1192-1201.
*/

static double park_rng(my_pthread_fastmutex_t *mp)
{
  mp->rng_state= ((my_ulonglong)mp->rng_state * 279470273U) % 4294967291U;
  return (mp->rng_state / 2147483647.0);
}

int my_pthread_fastmutex_lock(my_pthread_fastmutex_t *mp)
{
  int   res;
  uint  i;
  uint  maxdelay= MY_PTHREAD_FASTMUTEX_DELAY;

  for (i= 0; i < mp->spins; i++)
  {
    res= pthread_mutex_trylock(&mp->mutex);

    if (res == 0)
      return 0;

    if (res != EBUSY)
      return res;

    mutex_delay(maxdelay);
    maxdelay += park_rng(mp) * MY_PTHREAD_FASTMUTEX_DELAY + 1;
  }
  return pthread_mutex_lock(&mp->mutex);
}


void fastmutex_global_init(void)
{
#ifdef _SC_NPROCESSORS_CONF
  cpu_count= sysconf(_SC_NPROCESSORS_CONF);
#endif
}
  
#endif /* defined(THREAD) && defined(MY_PTHREAD_FASTMUTEX) && !defined(SAFE_MUTEX) */ 
