Adding upstream version 1:10.11.6.upstream/1%10.11.6upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 672 insertions, 0 deletions

diff --git a/storage/maria/tablockman.c b/storage/maria/tablockman.c
new file mode 100644
index 00000000..180487a8
--- /dev/null
+++ b/storage/maria/tablockman.c
@@ -0,0 +1,672 @@
+/* QQ: TODO - allocate everything from dynarrays !!! (benchmark) */
+/* QQ: automatically place S instead of LS if possible */
+/* Copyright (C) 2006 MySQL AB
+
+   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., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1335 USA */
+
+#include <my_base.h>
+#include <hash.h>
+#include "tablockman.h"
+
+/*
+  Lock Manager for Table Locks
+
+  The code below handles locks on resources - but it is optimized for a
+  case when a number of resources is not very large, and there are many of
+  locks per resource - that is a resource is likely to be a table or a
+  database, but hardly a row in a table.
+
+  Locks belong to "lock owners". A Lock Owner is uniquely identified by a
+  16-bit number - loid (lock owner identifier). A function loid_to_tlo must
+  be provided by the application that takes such a number as an argument
+  and returns a TABLE_LOCK_OWNER structure.
+
+  Lock levels are completely defined by three tables. Lock compatibility
+  matrix specifies which locks can be held at the same time on a resource.
+  Lock combining matrix specifies what lock level has the same behaviour as
+  a pair of two locks of given levels. getlock_result matrix simplifies
+  intention locking and lock escalation for an application, basically it
+  defines which locks are intention locks and which locks are "loose"
+  locks.  It is only used to provide better diagnostics for the
+  application, lock manager itself does not differentiate between normal,
+  intention, and loose locks.
+
+  The assumptions are: few distinct resources, many locks are held at the
+  same time on one resource. Thus: a lock structure _per resource_ can be
+  rather large; a lock structure _per lock_ does not need to be very small
+  either; we need to optimize for _speed_. Operations we need are: place a
+  lock, check if a particular transaction already has a lock on this
+  resource, check if a conflicting lock exists, if yes - find who owns it.
+
+  Solution: every resource has a structure with
+  1. Hash of latest (see the lock upgrade section below) granted locks with
+     loid as a key. Thus, checking if a given transaction has a lock on
+     this resource is O(1) operation.
+  2. Doubly-linked lists of all granted locks - one list for every lock
+     type. Thus, checking if a conflicting lock exists is a check whether
+     an appropriate list head pointer is not null, also O(1).
+  3. Every lock has a loid of the owner, thus checking who owns a
+     conflicting lock is also O(1).
+  4. Deque of waiting locks. It's a deque (double-ended queue) not a fifo,
+     because for lock upgrades requests are added to the queue head, not
+     tail. This is a single place where there it gets O(N) on number
+     of locks - when a transaction wakes up from waiting on a condition,
+     it may need to scan the queue backward to the beginning to find
+     a conflicting lock. It is guaranteed though that "all transactions
+     before it" received the same - or earlier - signal.  In other words a
+     transaction needs to scan all transactions before it that received the
+     signal but didn't have a chance to resume the execution yet, so
+     practically OS scheduler won't let the scan to be O(N).
+
+  Waiting: if there is a conflicting lock or if wait queue is not empty, a
+  requested lock cannot be granted at once. It is added to the end of the
+  wait queue. If a queue was empty and there is a conflicting lock - the
+  "blocker" transaction is the owner of this lock. If a queue is not empty,
+  an owner of the previous lock in the queue is the "blocker". But if the
+  previous lock is compatible with the request, then the "blocker" is the
+  transaction that the owner of the lock at the end of the queue is waiting
+  for (in other words, our lock is added to the end of the wait queue, and
+  our blocker is the same as of the lock right before us).
+
+  Lock upgrades: when a thread that has a lock on a given resource,
+  requests a new lock on the same resource and the old lock is not enough
+  to satisfy new lock requirements (which is defined by
+  lock_combining_matrix[old_lock][new_lock] != old_lock), a new lock
+  (defined by lock_combining_matrix as above) is placed. Depending on
+  other granted locks it is immediately granted or it has to wait.  Here the
+  lock is added to the start of the waiting queue, not to the end.  Old
+  lock, is removed from the hash, but not from the doubly-linked lists.
+  (indeed, a transaction checks "do I have a lock on this resource ?" by
+  looking in a hash, and it should find a latest lock, so old locks must be
+  removed; but a transaction checks "are there conflicting locks ?" by
+  checking doubly-linked lists, it doesn't matter if it will find an old
+  lock - if it would be removed, a new lock would be also a conflict).
+  So, a hash contains only "latest" locks - there can be only one latest
+  lock per resource per transaction. But doubly-linked lists contain all
+  locks, even "obsolete" ones, because it doesnt't hurt. Note that old
+  locks can not be freed early, in particular they stay in the
+  'active_locks' list of a lock owner, because they may be "re-enabled"
+  on a savepoint rollback.
+
+  To better support table-row relations where one needs to lock the table
+  with an intention lock before locking the row, extended diagnostics is
+  provided.  When an intention lock (presumably on a table) is granted,
+  lockman_getlock() returns one of GOT_THE_LOCK (no need to lock the row,
+  perhaps the thread already has a normal lock on this table),
+  GOT_THE_LOCK_NEED_TO_LOCK_A_SUBRESOURCE (need to lock the row, as usual),
+  GOT_THE_LOCK_NEED_TO_INSTANT_LOCK_A_SUBRESOURCE (only need to check
+  whether it's possible to lock the row, but no need to lock it - perhaps
+  the thread has a loose lock on this table). This is defined by
+  getlock_result[] table.
+
+  Instant duration locks are not supported. Though they're trivial to add,
+  they are normally only used on rows, not on tables. So, presumably,
+  they are not needed here.
+
+  Mutexes: there're table mutexes (LOCKED_TABLE::mutex), lock owner mutexes
+  (TABLE_LOCK_OWNER::mutex), and a pool mutex (TABLOCKMAN::pool_mutex).
+  table mutex protects operations on the table lock structures, and lock
+  owner pointers waiting_for and waiting_for_loid.
+  lock owner mutex is only used to wait on lock owner condition
+  (TABLE_LOCK_OWNER::cond), there's no need to protect owner's lock
+  structures, and only lock owner itself may access them.
+  The pool mutex protects a pool of unused locks. Note the locking order:
+  first the table mutex, then the owner mutex or a pool mutex.
+  Table mutex lock cannot be attempted when owner or pool mutex are locked.
+  No mutex lock can be attempted if owner or pool mutex are locked.
+*/
+
+/*
+  Lock compatibility matrix.
+
+  It's asymmetric. Read it as "Somebody has the lock <value in the row
+  label>, can I set the lock <value in the column label> ?"
+
+  ') Though you can take LS lock while somebody has S lock, it makes no
+  sense - it's simpler to take S lock too.
+
+  1  - compatible
+  0  - incompatible
+  -1 - "impossible", so that we can assert the impossibility.
+*/
+static const int lock_compatibility_matrix[10][10]=
+{ /* N    S   X  IS  IX  SIX LS  LX  SLX LSIX          */
+  {  -1, -1, -1, -1, -1, -1, -1, -1, -1, -1 }, /* N    */
+  {  -1,  1,  0,  1,  0,  0,  1,  0,  0,  0 }, /* S    */
+  {  -1,  0,  0,  0,  0,  0,  0,  0,  0,  0 }, /* X    */
+  {  -1,  1,  0,  1,  1,  1,  1,  1,  1,  1 }, /* IS   */
+  {  -1,  0,  0,  1,  1,  0,  1,  1,  0,  1 }, /* IX   */
+  {  -1,  0,  0,  1,  0,  0,  1,  0,  0,  0 }, /* SIX  */
+  {  -1,  1,  0,  1,  0,  0,  1,  0,  0,  0 }, /* LS   */
+  {  -1,  0,  0,  0,  0,  0,  0,  0,  0,  0 }, /* LX   */
+  {  -1,  0,  0,  0,  0,  0,  0,  0,  0,  0 }, /* SLX  */
+  {  -1,  0,  0,  1,  0,  0,  1,  0,  0,  0 }  /* LSIX */
+};
+
+/*
+  Lock combining matrix.
+
+  It's symmetric. Read it as "what lock level L is identical to the
+  set of two locks A and B"
+
+  One should never get N from it, we assert the impossibility
+*/
+static const enum lockman_lock_type lock_combining_matrix[10][10]=
+{/*    N    S   X    IS    IX  SIX    LS    LX   SLX   LSIX         */
+  {    N,   N,  N,    N,    N,   N,    N,    N,   N,    N}, /* N    */
+  {    N,   S,  X,    S,  SIX, SIX,    S,  SLX, SLX,  SIX}, /* S    */
+  {    N,   X,  X,    X,    X,   X,    X,    X,   X,    X}, /* X    */
+  {    N,   S,  X,   IS,   IX, SIX,   LS,   LX, SLX, LSIX}, /* IS   */
+  {    N, SIX,  X,   IX,   IX, SIX, LSIX,   LX, SLX, LSIX}, /* IX   */
+  {    N, SIX,  X,  SIX,  SIX, SIX,  SIX,  SLX, SLX,  SIX}, /* SIX  */
+  {    N,   S,  X,   LS, LSIX, SIX,   LS,   LX, SLX, LSIX}, /* LS   */
+  {    N, SLX,  X,   LX,   LX, SLX,   LX,   LX, SLX,   LX}, /* LX   */
+  {    N, SLX,  X,  SLX,  SLX, SLX,  SLX,  SLX, SLX,  SLX}, /* SLX  */
+  {    N, SIX,  X, LSIX, LSIX, SIX, LSIX,   LX, SLX, LSIX}  /* LSIX */
+};
+
+/*
+  the return codes for lockman_getlock
+
+  It's asymmetric. Read it as "I have the lock <value in the row label>,
+  what value should be returned for <value in the column label> ?"
+
+  0 means impossible combination (assert!)
+
+  Defines below help to preserve the table structure.
+  I/L/A values are self explanatory
+  x means the combination is possible (assert should not crash)
+    but it cannot happen in row locks, only in table locks (S,X),
+    or lock escalations (LS,LX)
+*/
+#define I GOT_THE_LOCK_NEED_TO_LOCK_A_SUBRESOURCE
+#define L GOT_THE_LOCK_NEED_TO_INSTANT_LOCK_A_SUBRESOURCE
+#define A GOT_THE_LOCK
+#define x GOT_THE_LOCK
+static const enum lockman_getlock_result getlock_result[10][10]=
+{/*    N    S   X    IS    IX  SIX    LS    LX   SLX   LSIX         */
+  {    0,   0,  0,    0,    0,   0,    0,    0,   0,    0}, /* N    */
+  {    0,   x,  0,    A,    0,   0,    x,    0,   0,    0}, /* S    */
+  {    0,   x,  x,    A,    A,   0,    x,    x,   0,    0}, /* X    */
+  {    0,   0,  0,    I,    0,   0,    0,    0,   0,    0}, /* IS   */
+  {    0,   0,  0,    I,    I,   0,    0,    0,   0,    0}, /* IX   */
+  {    0,   x,  0,    A,    I,   0,    x,    0,   0,    0}, /* SIX  */
+  {    0,   0,  0,    L,    0,   0,    x,    0,   0,    0}, /* LS   */
+  {    0,   0,  0,    L,    L,   0,    x,    x,   0,    0}, /* LX   */
+  {    0,   x,  0,    A,    L,   0,    x,    x,   0,    0}, /* SLX  */
+  {    0,   0,  0,    L,    I,   0,    x,    0,   0,    0}  /* LSIX */
+};
+#undef I
+#undef L
+#undef A
+#undef x
+
+/*
+  this structure is optimized for a case when there're many locks
+  on the same resource - e.g. a table
+*/
+
+struct st_table_lock {
+  /* QQ: do we need upgraded_from ? */
+  struct st_table_lock *next_in_lo, *upgraded_from, *next, *prev;
+  struct st_locked_table *table;
+  uint16 loid;
+  uchar  lock_type;
+};
+
+static inline
+TABLE_LOCK *find_by_loid(LOCKED_TABLE *table, uint16 loid)
+{
+  return (TABLE_LOCK *)my_hash_search(& table->latest_locks,
+                                   (uchar *)& loid, sizeof(loid));
+}
+
+static inline
+void remove_from_wait_queue(TABLE_LOCK *lock, LOCKED_TABLE *table)
+{
+  DBUG_ASSERT(table == lock->table);
+  if (lock->prev)
+  {
+    DBUG_ASSERT(table->wait_queue_out != lock);
+    lock->prev->next= lock->next;
+  }
+  else
+  {
+    DBUG_ASSERT(table->wait_queue_out == lock);
+    table->wait_queue_out= lock->next;
+  }
+  if (lock->next)
+  {
+    DBUG_ASSERT(table->wait_queue_in != lock);
+    lock->next->prev= lock->prev;
+  }
+  else
+  {
+    DBUG_ASSERT(table->wait_queue_in == lock);
+    table->wait_queue_in= lock->prev;
+  }
+}
+
+/*
+  DESCRIPTION
+    tries to lock a resource 'table' with a lock level 'lock'.
+
+  RETURN
+    see enum lockman_getlock_result
+*/
+enum lockman_getlock_result
+tablockman_getlock(TABLOCKMAN *lm, TABLE_LOCK_OWNER *lo,
+                   LOCKED_TABLE *table, enum lockman_lock_type lock)
+{
+  TABLE_LOCK *old, *new, *blocker, *blocker2;
+  TABLE_LOCK_OWNER *wait_for;
+  struct timespec timeout;
+  enum lockman_lock_type new_lock;
+  enum lockman_getlock_result res;
+  int i;
+
+  DBUG_ASSERT(lo->waiting_lock == 0);
+  DBUG_ASSERT(lo->waiting_for == 0);
+  DBUG_ASSERT(lo->waiting_for_loid == 0);
+
+  mysql_mutex_lock(& table->mutex);
+  /* do we already have a lock on this resource ? */
+  old= find_by_loid(table, lo->loid);
+
+  /* calculate the level of the upgraded lock, if yes */
+  new_lock= old ? lock_combining_matrix[old->lock_type][lock] : lock;
+
+  /* and check if old lock is enough to satisfy the new request */
+  if (old && new_lock == old->lock_type)
+  {
+    /* yes */
+    res= getlock_result[old->lock_type][lock];
+    goto ret;
+  }
+
+  /* no, placing a new lock. first - take a free lock structure from the pool */
+  mysql_mutex_lock(& lm->pool_mutex);
+  new= lm->pool;
+  if (new)
+  {
+    lm->pool= new->next;
+    mysql_mutex_unlock(& lm->pool_mutex);
+  }
+  else
+  {
+    mysql_mutex_unlock(& lm->pool_mutex);
+    new= (TABLE_LOCK *)my_malloc(sizeof(*new), MYF(MY_WME));
+    if (unlikely(!new))
+    {
+      res= NO_MEMORY_FOR_LOCK;
+      goto ret;
+    }
+  }
+
+  new->loid= lo->loid;
+  new->lock_type= new_lock;
+  new->table= table;
+
+  /* and try to place it */
+  for (new->prev= table->wait_queue_in;;)
+  {
+    wait_for= 0;
+    if (!old)
+    {
+      /* not upgrading - a lock must be added to the _end_ of the wait queue */
+      for (blocker= new->prev; blocker && !wait_for; blocker= blocker->prev)
+      {
+        TABLE_LOCK_OWNER *tmp= lm->loid_to_tlo(blocker->loid);
+
+        /* find a blocking lock */
+        DBUG_ASSERT(table->wait_queue_out);
+        DBUG_ASSERT(table->wait_queue_in);
+        if (!lock_compatibility_matrix[blocker->lock_type][lock])
+        {
+          /* found! */
+          wait_for= tmp;
+          break;
+        }
+
+        /*
+          hmm, the lock before doesn't block us, let's look one step further.
+          the condition below means:
+
+            if we never waited on a condition yet
+            OR
+            the lock before ours (blocker) waits on a lock (blocker2) that is
+               present in the hash AND and conflicts with 'blocker'
+
+            the condition after OR may fail if 'blocker2' was removed from
+            the hash, its signal woke us up, but 'blocker' itself didn't see
+            the signal yet.
+        */
+        if (!lo->waiting_lock ||
+            ((blocker2= find_by_loid(table, tmp->waiting_for_loid)) &&
+            !lock_compatibility_matrix[blocker2->lock_type]
+                                      [blocker->lock_type]))
+        {
+          /* but it's waiting for a real lock. we'll wait for the same lock */
+          wait_for= tmp->waiting_for;
+          /*
+            We don't really need tmp->waiting_for, as tmp->waiting_for_loid
+            is enough.  waiting_for is just a local cache to avoid calling
+            loid_to_tlo().
+            But it's essensial that tmp->waiting_for pointer can ONLY
+            be dereferenced if find_by_loid() above returns a non-null
+            pointer, because a TABLE_LOCK_OWNER object that it points to
+            may've been freed when we come here after a signal.
+            In particular tmp->waiting_for_loid cannot be replaced
+            with tmp->waiting_for->loid.
+          */
+          DBUG_ASSERT(wait_for == lm->loid_to_tlo(tmp->waiting_for_loid));
+          break;
+        }
+
+        /*
+          otherwise - a lock it's waiting for doesn't exist.
+          We've no choice but to scan the wait queue backwards, looking
+          for a conflicting lock or a lock waiting for a real lock.
+          QQ is there a way to avoid this scanning ?
+        */
+      }
+    }
+
+    if (wait_for == 0)
+    {
+      /* checking for compatibility with existing locks */
+      for (blocker= 0, i= 0; i < LOCK_TYPES; i++)
+      {
+        if (table->active_locks[i] && !lock_compatibility_matrix[i+1][lock])
+        {
+          blocker= table->active_locks[i];
+          /* if the first lock in the list is our own - skip it */
+          if (blocker->loid == lo->loid)
+            blocker= blocker->next;
+          if (blocker) /* found a conflicting lock, need to wait */
+            break;
+        }
+      }
+      if (!blocker) /* free to go */
+        break;
+      wait_for= lm->loid_to_tlo(blocker->loid);
+    }
+
+    /* ok, we're here - the wait is inevitable */
+    lo->waiting_for= wait_for;
+    lo->waiting_for_loid= wait_for->loid;
+    if (!lo->waiting_lock) /* first iteration of the for() loop */
+    {
+      /* lock upgrade or new lock request ? */
+      if (old)
+      {
+        /* upgrade - add the lock to the _start_ of the wait queue */
+        new->prev= 0;
+        if ((new->next= table->wait_queue_out))
+          new->next->prev= new;
+        table->wait_queue_out= new;
+        if (!table->wait_queue_in)
+          table->wait_queue_in= table->wait_queue_out;
+      }
+      else
+      {
+        /* new lock - add the lock to the _end_ of the wait queue */
+        new->next= 0;
+        if ((new->prev= table->wait_queue_in))
+          new->prev->next= new;
+        table->wait_queue_in= new;
+        if (!table->wait_queue_out)
+          table->wait_queue_out= table->wait_queue_in;
+      }
+      lo->waiting_lock= new;
+
+      set_timespec_nsec(timeout,lm->lock_timeout * 1000000);
+
+    }
+
+    /*
+      prepare to wait.
+      we must lock blocker's mutex to wait on blocker's cond.
+      and we must release table's mutex.
+      note that blocker's mutex is locked _before_ table's mutex is released
+    */
+    mysql_mutex_lock(wait_for->mutex);
+    mysql_mutex_unlock(& table->mutex);
+
+    /* now really wait */
+    i= mysql_cond_timedwait(wait_for->cond, wait_for->mutex, & timeout);
+
+    mysql_mutex_unlock(wait_for->mutex);
+
+    if (i == ETIMEDOUT || i == ETIME)
+    {
+      /* we rely on the caller to rollback and release all locks */
+      res= LOCK_TIMEOUT;
+      goto ret2;
+    }
+
+    mysql_mutex_lock(& table->mutex);
+
+    /* ... and repeat from the beginning */
+  }
+  /* yeah! we can place the lock now */
+
+  /* remove the lock from the wait queue, if it was there */
+  if (lo->waiting_lock)
+  {
+    remove_from_wait_queue(new, table);
+    lo->waiting_lock= 0;
+    lo->waiting_for= 0;
+    lo->waiting_for_loid= 0;
+  }
+
+  /* add it to the list of all locks of this lock owner */
+  new->next_in_lo= lo->active_locks;
+  lo->active_locks= new;
+
+  /* and to the list of active locks of this lock type */
+  new->prev= 0;
+  if ((new->next= table->active_locks[new_lock-1]))
+    new->next->prev= new;
+  table->active_locks[new_lock-1]= new;
+
+  /* update the latest_locks hash */
+  if (old)
+    my_hash_delete(& table->latest_locks, (uchar *)old);
+  my_hash_insert(& table->latest_locks, (uchar *)new);
+
+  new->upgraded_from= old;
+
+  res= getlock_result[lock][lock];
+
+ret:
+  mysql_mutex_unlock(& table->mutex);
+ret2:
+  DBUG_ASSERT(res);
+  return res;
+}
+
+/*
+  DESCRIPTION
+    release all locks belonging to a transaction.
+    signal waiters to continue
+*/
+void tablockman_release_locks(TABLOCKMAN *lm, TABLE_LOCK_OWNER *lo)
+{
+  TABLE_LOCK *lock, *local_pool= 0, *local_pool_end;
+
+  /*
+    instead of adding released locks to a pool one by one, we'll link
+    them in a list and add to a pool in one short action (under a mutex)
+  */
+  local_pool_end= lo->waiting_lock ? lo->waiting_lock : lo->active_locks;
+  if (!local_pool_end)
+    return;
+
+  /* release a waiting lock, if any */
+  if ((lock= lo->waiting_lock))
+  {
+    DBUG_ASSERT(lock->loid == lo->loid);
+    mysql_mutex_lock(& lock->table->mutex);
+    remove_from_wait_queue(lock, lock->table);
+
+    /*
+      a special case: if this lock was not the last in the wait queue
+      and it's compatible with the next lock, than the next lock
+      is waiting for our blocker though really it waits for us, indirectly.
+      Signal our blocker to release this next lock (after we removed our
+      lock from the wait queue, of course).
+    */
+    /*
+      An example to clarify the above:
+        trn1> S-lock the table. Granted.
+        trn2> IX-lock the table. Added to the wait queue. trn2 waits on trn1
+        trn3> IS-lock the table.  The queue is not empty, so IS-lock is added
+              to the queue. It's compatible with the waiting IX-lock, so trn3
+              waits for trn2->waiting_for, that is trn1.
+      if trn1 releases the lock it signals trn1->cond and both waiting
+      transactions are awaken. But if trn2 times out, trn3 must be notified
+      too (as IS and S locks are compatible). So trn2 must signal trn1->cond.
+    */
+    if (lock->next &&
+        lock_compatibility_matrix[lock->next->lock_type][lock->lock_type])
+    {
+      mysql_mutex_lock(lo->waiting_for->mutex);
+      mysql_cond_broadcast(lo->waiting_for->cond);
+      mysql_mutex_unlock(lo->waiting_for->mutex);
+    }
+    lo->waiting_for= 0;
+    lo->waiting_for_loid= 0;
+    mysql_mutex_unlock(& lock->table->mutex);
+
+    lock->next= local_pool;
+    local_pool= lock;
+  }
+
+  /* now release granted locks */
+  lock= lo->active_locks;
+  while (lock)
+  {
+    TABLE_LOCK *cur= lock;
+    mysql_mutex_t *mutex= & lock->table->mutex;
+    DBUG_ASSERT(cur->loid == lo->loid);
+
+    DBUG_ASSERT(lock != lock->next_in_lo);
+    lock= lock->next_in_lo;
+
+    /* TODO ? group locks by table to reduce the number of mutex locks */
+    mysql_mutex_lock(mutex);
+    my_hash_delete(& cur->table->latest_locks, (uchar *)cur);
+
+    if (cur->prev)
+      cur->prev->next= cur->next;
+    if (cur->next)
+      cur->next->prev= cur->prev;
+    if (cur->table->active_locks[cur->lock_type-1] == cur)
+      cur->table->active_locks[cur->lock_type-1]= cur->next;
+
+    cur->next= local_pool;
+    local_pool= cur;
+
+    mysql_mutex_unlock(mutex);
+  }
+
+  lo->waiting_lock= lo->active_locks= 0;
+
+  /*
+    okay, all locks released. now signal that we're leaving,
+    in case somebody's waiting for it
+  */
+  mysql_mutex_lock(lo->mutex);
+  mysql_cond_broadcast(lo->cond);
+  mysql_mutex_unlock(lo->mutex);
+
+  /* and push all freed locks to the lockman's pool */
+  mysql_mutex_lock(& lm->pool_mutex);
+  local_pool_end->next= lm->pool;
+  lm->pool= local_pool;
+  mysql_mutex_unlock(& lm->pool_mutex);
+}
+
+void tablockman_init(TABLOCKMAN *lm, loid_to_tlo_func *func, uint timeout)
+{
+  lm->pool= 0;
+  lm->loid_to_tlo= func;
+  lm->lock_timeout= timeout;
+  mysql_mutex_init(& lm->pool_mutex, MY_MUTEX_INIT_FAST);
+  my_interval_timer(); /* ensure that my_interval_timer() is initialized */
+}
+
+void tablockman_destroy(TABLOCKMAN *lm)
+{
+  while (lm->pool)
+  {
+    TABLE_LOCK *tmp= lm->pool;
+    lm->pool= tmp->next;
+    my_free(tmp);
+  }
+  mysql_mutex_destroy(& lm->pool_mutex);
+}
+
+/*
+  initialize a LOCKED_TABLE structure
+
+  SYNOPSYS
+    lt                          a LOCKED_TABLE to initialize
+    initial_hash_size           initial size for 'latest_locks' hash
+*/
+void tablockman_init_locked_table(LOCKED_TABLE *lt, int initial_hash_size)
+{
+  bzero(lt, sizeof(*lt));
+  mysql_mutex_init(& lt->mutex, MY_MUTEX_INIT_FAST);
+  my_hash_init(& lt->latest_locks, & my_charset_bin, initial_hash_size,
+            offsetof(TABLE_LOCK, loid),
+            sizeof(((TABLE_LOCK*)0)->loid), 0, 0, 0);
+}
+
+void tablockman_destroy_locked_table(LOCKED_TABLE *lt)
+{
+  int i;
+
+  DBUG_ASSERT(lt->wait_queue_out == 0);
+  DBUG_ASSERT(lt->wait_queue_in == 0);
+  DBUG_ASSERT(lt->latest_locks.records == 0);
+  for (i= 0; i<LOCK_TYPES; i++)
+     DBUG_ASSERT(lt->active_locks[i] == 0);
+
+  my_hash_free(& lt->latest_locks);
+  mysql_mutex_destroy(& lt->mutex);
+}
+
+#ifdef EXTRA_DEBUG
+static const char *lock2str[LOCK_TYPES+1]= {"N", "S", "X", "IS", "IX", "SIX",
+  "LS", "LX", "SLX", "LSIX"};
+
+void tablockman_print_tlo(TABLE_LOCK_OWNER *lo)
+{
+  TABLE_LOCK *lock;
+
+  printf("lo%d>", lo->loid);
+  if ((lock= lo->waiting_lock))
+    printf(" (%s.0x%lx)", lock2str[lock->lock_type], (ulong)lock->table);
+  for (lock= lo->active_locks;
+       lock && lock != lock->next_in_lo;
+       lock= lock->next_in_lo)
+    printf(" %s.0x%lx", lock2str[lock->lock_type], (ulong)lock->table);
+  if (lock && lock == lock->next_in_lo)
+    printf("!");
+  printf("\n");
+}
+#endif
+