post-review fixes

include/atomic/generic-msvc.h:
  prevent possible compiler warnings
include/lf.h:
  comments, better definition for LF_HASH_OVERHEAD
include/maria.h:
  define MARIA_CANNOT_ROLLBACK here
include/my_pthread.h:
  avoid possible name clash
include/waiting_threads.h:
  comments, const, move WT_RESOURCE to waiting_threads.c
mysql-test/suite/maria/r/maria_notembedded.result:
  new test
mysql-test/suite/maria/t/maria_notembedded.test:
  new test - 5-way deadlock
mysys/lf_hash.c:
  better definition for LF_HASH_OVERHEAD
mysys/my_static.c:
  comment
mysys/my_thr_init.c:
  casts
mysys/waiting_threads.c:
  comments, asserts, etc
server-tools/instance-manager/parse.cc:
  fix my_init_dynamic_array() to follow new calling conventions
sql/mysqld.cc:
  call wt_init after set_proper_floating_point_mode
sql/sql_class.h:
  comment
storage/maria/ha_maria.cc:
  move MARIA_CANNOT_ROLLBACK to a common header
storage/maria/ma_commit.c:
  comment
storage/maria/ma_write.c:
  comments, check for HA_ERR_FOUND_DUPP_KEY
storage/maria/trnman.c:
  comments, assert
storage/maria/trnman.h:
  comments
storage/maria/unittest/trnman-t.c:
  be paranoid
unittest/mysys/lf-t.c:
  comments
unittest/mysys/waiting_threads-t.c:
  comments, safety, memory leak

include/atomic/generic-msvc.h

-/* Copyright (C) 2006 MySQL AB
+/* Copyright (C) 2006-2008 MySQL AB, 2008-2009 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
@@ -55,7 +55,7 @@ LONG _InterlockedExchangeAdd (LONG volatile *Addend, LONG Value);
 #define IL_EXCHG_ADD32(X,Y)     InterlockedExchangeAdd((volatile LONG *)(X),(Y))
 #define IL_COMP_EXCHG32(X,Y,Z)  InterlockedCompareExchange((volatile LONG *)(X),(Y),(Z))
 #define IL_COMP_EXCHGptr        InterlockedCompareExchangePointer
-#define IL_EXCHG32       InterlockedExchange
+#define IL_EXCHG32(X,Y)         InterlockedExchange((volatile LONG *)(X),(Y))
 #define IL_EXCHGptr             InterlockedExchangePointer
 #define make_atomic_add_body(S) \
   v= IL_EXCHG_ADD ## S (a, v)

include/lf.h

-/* Copyright (C) 2007 MySQL AB
+/* Copyright (C) 2007-2008 MySQL AB, 2008-2009 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
@@ -187,8 +187,8 @@ typedef struct st_lf_allocator {
   uchar * volatile top;
   uint element_size;
   uint32 volatile mallocs;
-  void (*constructor)(uchar *);
-  void (*destructor)(uchar *);
+  void (*constructor)(uchar *); /* called, when an object is malloc()'ed */
+  void (*destructor)(uchar *);  /* called, when an object is free()'d    */
 } LF_ALLOCATOR;
 
 void lf_alloc_init(LF_ALLOCATOR *allocator, uint size, uint free_ptr_offset);
@@ -219,7 +219,7 @@ lock_wrap(lf_alloc_new, void *,
 #define LF_HASH_UNIQUE 1
 
 /* lf_hash overhead per element (that is, sizeof(LF_SLIST) */
-#define LF_HASH_OVERHEAD (sizeof(int*)*4)
+extern const int LF_HASH_OVERHEAD;
 
 typedef struct {
   LF_DYNARRAY array;                    /* hash itself */

include/maria.h

-/* Copyright (C) 2006 MySQL AB
+/* Copyright (C) 2006-2008 MySQL AB, 2008-2009 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
@@ -33,6 +33,8 @@ extern "C" {
 #include <myisamchk.h>
 #include <mysql/plugin.h>
 
+#define MARIA_CANNOT_ROLLBACK
+
 /*
   Limit max keys according to HA_MAX_POSSIBLE_KEY; See myisamchk.h for details
 */

include/my_pthread.h

-/* Copyright (C) 2000 MySQL AB
+/* Copyright (C) 2000-2008 MySQL AB, 2008-2009 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
@@ -430,19 +430,19 @@ int my_pthread_mutex_trylock(pthread_mutex_t *mutex);
 
 /* adapt for two different flavors of struct timespec */
 #ifdef HAVE_TIMESPEC_TS_SEC
-#define TV_sec  ts_sec
-#define TV_nsec ts_nsec
+#define MY_tv_sec  ts_sec
+#define MY_tv_nsec ts_nsec
 #else
-#define TV_sec  tv_sec
-#define TV_nsec tv_nsec
+#define MY_tv_sec  tv_sec
+#define MY_tv_nsec tv_nsec
 #endif /* HAVE_TIMESPEC_TS_SEC */
 
 #ifndef set_timespec_time_nsec
 #define set_timespec_time_nsec(ABSTIME,TIME,NSEC) do {                  \
   ulonglong nsec= (NSEC);                                               \
   ulonglong now= (TIME) + (nsec/100);                                   \
-  (ABSTIME).TV_sec=  (now / ULL(10000000));                             \
-  (ABSTIME).TV_nsec= (now % ULL(10000000) * 100 + (nsec % 100));        \
+  (ABSTIME).MY_tv_sec=  (now / ULL(10000000));                          \
+  (ABSTIME).MY_tv_nsec= (now % ULL(10000000) * 100 + (nsec % 100));     \
 } while(0)
 #endif /* !set_timespec_time_nsec */
 

include/waiting_threads.h

-/* Copyright (C) 2008 MySQL AB
+/* Copyright (C) 2008 MySQL AB, 2008-2009 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
@@ -24,16 +24,18 @@
 C_MODE_START
 
 typedef struct st_wt_resource_id WT_RESOURCE_ID;
+typedef struct st_wt_resource WT_RESOURCE;
 
 typedef struct st_wt_resource_type {
-  int (*compare)(void *a, void *b);
-  const void *(*make_key)(WT_RESOURCE_ID *id, uint *len);
+  my_bool (*compare)(const void *a, const void *b);
+  const void *(*make_key)(const WT_RESOURCE_ID *id, uint *len); /* not used */
 } WT_RESOURCE_TYPE;
 
 struct st_wt_resource_id {
   ulonglong value;
-  WT_RESOURCE_TYPE *type;
+  const WT_RESOURCE_TYPE *type;
 };
+/* the below differs from sizeof(WT_RESOURCE_ID) by the amount of padding */
 #define sizeof_WT_RESOURCE_ID (sizeof(ulonglong)+sizeof(void*))
 
 #define WT_WAIT_STATS  24
@@ -43,93 +45,17 @@ extern uint32    wt_wait_stats[WT_WAIT_STATS+1];
 extern uint32    wt_cycle_stats[2][WT_CYCLE_STATS+1];
 extern uint32    wt_success_stats;
 
-/*
-  'lock' protects 'owners', 'state', and 'waiter_count'
-  'id' is read-only
-
-  a resource is picked up from a hash in a lock-free manner
-  it's returned pinned, so it cannot be freed at once
-  but it may be freed right after the pin is removed
-  to free a resource it should be
-    1. have no owners
-    2. have no waiters
-
-  two ways to access a resource:
-    1. find it in a hash
-       - it's returned pinned.
-        a) take a lock in exclusive mode
-        b) check the state, it should be ACTIVE
-        c) unpin
-    2. by a direct reference
-       - could only used if a resource cannot be freed
-       e.g. accessing a resource by thd->waiting_for is safe,
-       a resource cannot be freed as there's a thread waiting for it
-*/
-typedef struct st_wt_resource {
-  WT_RESOURCE_ID  id;
-  uint            waiter_count;
-  enum { ACTIVE, FREE } state;
-#ifndef DBUG_OFF
-  pthread_mutex_t  *mutex;
-#endif
-  /*
-    before the 'lock' all elements are mutable, after (and including) -
-    immutable in the sense that lf_hash_insert() won't memcpy() over them.
-    See wt_init().
-  */
-#ifdef WT_RWLOCKS_USE_MUTEXES
-  /*
-    we need a special rwlock-like 'lock' to allow readers bypass
-    waiting writers, otherwise readers can deadlock. For example:
-
-      A waits on resource x, owned by B, B waits on resource y, owned
-      by A, we have a cycle (A->x->B->y->A)
-      Both A and B start deadlock detection:
-
-        A locks x                          B locks y
-        A goes deeper                      B goes deeper
-        A locks y                          B locks x
-
-      with mutexes it would deadlock. With rwlocks it won't, as long
-      as both A and B are taking read locks (and they do).
-      But other threads may take write locks. Assume there's
-      C who wants to start waiting on x, and D who wants to start
-      waiting on y.
-
-        A read-locks x                       B read-locks y
-        A goes deeper                        B goes deeper
-     => C write-locks x (to add a new edge)  D write-locks y
-     .. C is blocked                         D is blocked
-        A read-locks y                       B read-locks x
-
-      Now, if a read lock can bypass a pending wrote lock request, we're fine.
-      If it can not, we have a deadlock.
-
-    writer starvation is technically possible, but unlikely, because
-    the contention is expected to be low.
-  */
-  struct {
-    pthread_cond_t   cond;
-    pthread_mutex_t  mutex;
-    uint readers: 16;
-    uint pending_writers: 15;
-    uint write_locked: 1;
-  } lock;
-#else
-  rw_lock_t lock;
-#endif
-  pthread_cond_t   cond;
-  DYNAMIC_ARRAY    owners;
-} WT_RESOURCE;
-
 typedef struct st_wt_thd {
   /*
     XXX
-    there's no protection (mutex) against concurrent access of
-    the dynarray below. it is assumed that a caller will have it
-    automatically (not to protect this array but to protect its
-    own - caller's - data structures, and we'll get it for free.
-    If not, we'll need to add a mutex
+    there's no protection (mutex) against concurrent access of the
+    dynarray below. it is assumed that a caller will have it anyway
+    (not to protect this array but to protect its own - caller's -
+    data structures), and we'll get it for free. A caller needs to
+    ensure that a blocker won't release a resource before a blocked
+    thread starts waiting, which is usually done with a mutex.
+    
+    If the above assumption is wrong, we'll need to add a mutex here.
   */
   DYNAMIC_ARRAY   my_resources;
   /*
@@ -141,8 +67,10 @@ typedef struct st_wt_thd {
   LF_PINS        *pins;
 
   /* pointers to values */
-  ulong *timeout_short, *deadlock_search_depth_short;
-  ulong *timeout_long, *deadlock_search_depth_long;
+  const ulong *timeout_short;
+  const ulong *deadlock_search_depth_short;
+  const ulong *timeout_long;
+  const ulong *deadlock_search_depth_long;
 
   /*
     weight relates to the desirability of a transaction being killed if it's
@@ -169,13 +97,13 @@ typedef struct st_wt_thd {
   */
   ulong volatile weight;
   /*
-    'killed' is indirectly protected by waiting_for->lock -
-    a killed thread needs to clear its 'waiting_for', and thus needs a lock.
+    'killed' is indirectly protected by waiting_for->lock because
+    a killed thread needs to clear its 'waiting_for' and thus needs a lock.
     That is a thread needs an exclusive lock to read 'killed' reliably.
     But other threads may change 'killed' from 0 to 1, a shared
     lock is enough for that.
    */
-  my_bool volatile killed;
+  my_bool killed;
 #ifndef DBUG_OFF
   const char     *name;
 #endif
@@ -189,13 +117,13 @@ typedef struct st_wt_thd {
 
 void wt_init(void);
 void wt_end(void);
-void wt_thd_lazy_init(WT_THD *, ulong *, ulong *, ulong *, ulong *);
+void wt_thd_lazy_init(WT_THD *, const ulong *, const ulong *, const ulong *, const ulong *);
 void wt_thd_destroy(WT_THD *);
-int wt_thd_will_wait_for(WT_THD *, WT_THD *, WT_RESOURCE_ID *);
+int wt_thd_will_wait_for(WT_THD *, WT_THD *, const WT_RESOURCE_ID *);
 int wt_thd_cond_timedwait(WT_THD *, pthread_mutex_t *);
-void wt_thd_release(WT_THD *, WT_RESOURCE_ID *);
+void wt_thd_release(WT_THD *, const WT_RESOURCE_ID *);
 #define wt_thd_release_all(THD) wt_thd_release((THD), 0)
-int wt_resource_id_memcmp(void *, void *);
+int wt_resource_id_memcmp(const void *, const void *);
 
 C_MODE_END
 

mysql-test/suite/maria/r/maria_notembedded.result

@@ -30,9 +30,24 @@ insert t1 values (2);
 lock table t1 write concurrent;
 insert t1 values (3);
 insert t1 values (2);
+lock table t1 write concurrent;
+insert t1 values (4);
 insert t1 values (3);
+lock table t1 write concurrent;
+insert t1 values (5);
+insert t1 values (4);
+lock table t1 write concurrent;
+insert t1 values (6);
+insert t1 values (5);
+insert t1 values (6);
 ERROR 40001: Deadlock found when trying to get lock; try restarting transaction
 unlock tables;
 ERROR 23000: Duplicate entry '2' for key 'a'
 unlock tables;
+ERROR 23000: Duplicate entry '3' for key 'a'
+unlock tables;
+ERROR 23000: Duplicate entry '4' for key 'a'
+unlock tables;
+ERROR 23000: Duplicate entry '5' for key 'a'
+unlock tables;
 drop table t1;

mysql-test/suite/maria/t/maria_notembedded.test

@@ -33,27 +33,64 @@ drop table t1;
 #
 create table t1 (a int unique) transactional=1;
 insert t1 values (1);
+
 lock table t1 write concurrent;
 insert t1 values (2);
-connect(con_d,localhost,root,,);
+
+connect(con_a,localhost,root,,);
 lock table t1 write concurrent;
 insert t1 values (3);
 send insert t1 values (2);
+
+connect(con_b,localhost,root,,);
+lock table t1 write concurrent;
+insert t1 values (4);
+send insert t1 values (3);
+
+connect(con_c,localhost,root,,);
+lock table t1 write concurrent;
+insert t1 values (5);
+send insert t1 values (4);
+
+connect(con_d,localhost,root,,);
+lock table t1 write concurrent;
+insert t1 values (6);
+send insert t1 values (5);
+
 connection default;
-let $wait_condition=select count(*) = 1 from information_schema.processlist where state="waiting for a resource";
+let $wait_condition=select count(*) = 4 from information_schema.processlist where state="waiting for a resource";
 --source include/wait_condition.inc
 --error ER_LOCK_DEADLOCK
-insert t1 values (3);
+insert t1 values (6);
 unlock tables;
+
+connection con_a;
+--error ER_DUP_ENTRY
+reap;
+unlock tables;
+disconnect con_a;
+
+connection con_b;
+--error ER_DUP_ENTRY
+reap;
+unlock tables;
+disconnect con_b;
+
+connection con_c;
+--error ER_DUP_ENTRY
+reap;
+unlock tables;
+disconnect con_c;
+
 connection con_d;
 --error ER_DUP_ENTRY
 reap;
 unlock tables;
 disconnect con_d;
+
 connection default;
 drop table t1;
 
-
 --disable_result_log
 --disable_query_log
 eval set session storage_engine=$default_engine;

mysys/lf_alloc-pin.c

 /* QQ: TODO multi-pinbox */
-/* Copyright (C) 2006 MySQL AB
+/* Copyright (C) 2006-2008 MySQL AB, 2008-2009 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
@@ -330,7 +330,7 @@ static void _lf_pinbox_real_free(LF_PINS *pins)
 {
   int npins, alloca_size;
   void *list, **addr;
-  uchar *first, *last= NULL;
+  void *first, *last= NULL;
   LF_PINBOX *pinbox= pins->pinbox;
 
   LINT_INIT(first);

mysys/lf_hash.c

-/* Copyright (C) 2006 MySQL AB
+/* Copyright (C) 2006-2008 MySQL AB, 2008-2009 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
@@ -42,6 +42,8 @@ typedef struct {
   */
 } LF_SLIST;
 
+const int LF_HASH_OVERHEAD= sizeof(LF_SLIST);
+
 /*
   a structure to pass the context (pointers two the three successive elements
   in a list) from lfind to linsert/ldelete
@@ -315,7 +317,6 @@ void lf_hash_init(LF_HASH *hash, uint element_size, uint flags,
                   uint key_offset, uint key_length, hash_get_key get_key,
                   CHARSET_INFO *charset)
 {
-  compile_time_assert(sizeof(LF_SLIST) == LF_HASH_OVERHEAD);
   lf_alloc_init(&hash->alloc, sizeof(LF_SLIST)+element_size,
                 offsetof(LF_SLIST, key));
   lf_dynarray_init(&hash->array, sizeof(LF_SLIST *));

mysys/my_static.c

-/* Copyright (C) 2000 MySQL AB
+/* Copyright (C) 2000-2008 MySQL AB, 2008-2009 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
@@ -101,6 +101,7 @@ static const char *proc_info_dummy(void *a __attribute__((unused)),
   return 0;
 }
 
+/* this is to be able to call set_thd_proc_info from the C code */
 const char *(*proc_info_hook)(void *, const char *, const char *, const char *,
                               const unsigned int)= proc_info_dummy;
 

mysys/my_thr_init.c

-/* Copyright (C) 2000 MySQL AB
+/* Copyright (C) 2000-2008 MySQL AB, 2008-2009 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
@@ -332,7 +332,8 @@ my_bool my_thread_init(void)
                         0);
   pthread_cond_init(&tmp->suspend, NULL);
 
-  tmp->stack_ends_here= &tmp + STACK_DIRECTION * my_thread_stack_size;
+  tmp->stack_ends_here= (char*)&tmp +
+                         STACK_DIRECTION * (long)my_thread_stack_size;
 
   pthread_mutex_lock(&THR_LOCK_threads);
   tmp->id= ++thread_id;

mysys/waiting_threads.c

-/* Copyright (C) 2008 MySQL AB
+/* Copyright (C) 2008 MySQL AB, 2008-2009 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
@@ -13,14 +13,16 @@
    along with this program; if not, write to the Free Software
    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA */
 
-/*
+/**
+  @file
+
   "waiting threads" subsystem - a unified interface for threads to wait
   on each other, with built-in deadlock detection.
 
   Main concepts
   ^^^^^^^^^^^^^
   a thread - is represented by a WT_THD structure. One physical thread
-      can have only one WT_THD descriptor.
+    can have only one WT_THD descriptor at any given moment.
 
   a resource - a thread does not wait for other threads directly,
     instead it waits for a "resource", which is "owned" by other threads.
@@ -37,9 +39,67 @@
     a function that knows how to compare values of this resource type.
     In the simple case it could be wt_resource_id_memcmp().
 
+  a wait-for graph - a graph, that represenst "wait-for" relationships.
+    It has two types of nodes - threads and resources. There are directed
+    edges from a thread to a resource it is waiting for (WT_THD::waiting_for),
+    from a thread to resources that it "owns" (WT_THD::my_resources),
+    and from a resource to threads that "own" it (WT_RESOURCE::owners)
+
+  Graph completeness
+  ^^^^^^^^^^^^^^^^^^
+
+  For flawless deadlock detection wait-for graph must be complete.
+  It means that when a thread starts waiting it needs to know *all* its
+  blockers, and call wt_thd_will_wait_for() for every one of them.
+  Otherwise two phenomena should be expected:
+
+  1. Fuzzy timeouts:
+
+    thread A needs to get a lock, and is blocked by a thread B.
+    it waits.
+    Just before the timeout thread B releases the lock.
+    thread A is ready to grab the lock but discovers that it is also
+    blocked by a thread C.
+    It waits and times out.
+
+    As a result thread A has waited two timeout intervals, instead of one.
+
+  2. Unreliable cycle detection:
+
+     Thread A waits for threads B and C
+     Thread C waits for D
+     Thread D wants to start waiting for A
+
+     one can see immediately that thread D creates a cycle, and thus
+     a deadlock is detected.
+
+     But if thread A would only wait for B, and start waiting for C
+     when B would unlock, thread D would be allowed to wait, a deadlock
+     would be only detected when B unlocks or somebody times out.
+
+  These two phenomena don't affect a correctness, and strictly speaking,
+  the caller is not required to call wt_thd_will_wait_for() for *all*
+  blockers - it may optimize wt_thd_will_wait_for() calls. But they
+  may be perceived as bugs by users, it must be understood that such
+  an optimization comes with its price.
+
   Usage
   ^^^^^
-   to use the interface one needs to use this thread's WT_THD,
+
+  First, the wt* subsystem must be initialized by calling
+  wt_init(). In the server you don't need to do it, it's done
+  in mysqld.cc.
+
+  Similarly, wt_end() frees wt* structures, should be called
+  at the end, but in the server mysqld.cc takes care of that.
+
+  Every WT_THD should be initialized with wt_thd_lazy_init().
+  After that they can be used in other wt_thd_* calls.
+  Before discarding, WT_THD should be free'd with
+  wt_thd_destroy(). In the server both are handled in sql_class.cc,
+  it's an error to try to do it manually.
+
+  To use the deadlock detection one needs to use this thread's WT_THD,
   call wt_thd_will_wait_for() for every thread it needs to wait on,
   then call wt_thd_cond_timedwait(). When thread releases a resource
   it should call wt_thd_release() (or wt_thd_release_all()) - it will
@@ -48,7 +108,7 @@
 
   Just like with pthread's cond_wait, there could be spurious
   wake-ups from wt_thd_cond_timedwait(). A caller is expected to
-   handle that.
+  handle that (that is, to re-check the blocking criteria).
 
   wt_thd_will_wait_for() and wt_thd_cond_timedwait() return either
   WT_OK or WT_DEADLOCK. Additionally wt_thd_cond_timedwait() can return
@@ -79,8 +139,8 @@
   wt_thd_cond_timedwait()), a number of timeouts, a deadlock cycle
   length distribution - number of deadlocks with every length from
   1 to WT_CYCLE_STATS, and a wait time distribution - number
-   of waits with a time from 1 us to 1 min in WT_CYCLE_STATS
-   intervals on a log scale.
+  of waits with a time from 1 us to 1 min in WT_WAIT_STATS
+  intervals on a log e scale.
 */
 
 /*
@@ -93,10 +153,11 @@
 
       (example A=IX, B=IS, C=S, D=X)
 
-   you need to include lock level in the resource identifier - thread 1
-   waiting for lock A on resource R and thread 2 waiting for lock B
-   on resource R should wait on different WT_RESOURCE structures, on different
-   {lock, resource} pairs. Otherwise the following is possible:
+   you need to include lock level in the resource identifier - a
+   thread waiting for lock of the type A on resource R and another
+   thread waiting for lock of the type B on resource R should wait on
+   different WT_RESOURCE structures, on different {lock, resource}
+   pairs.  Otherwise the following is possible:
 
       thread1> take S-lock on R
       thread2> take IS-lock on R
@@ -113,40 +174,46 @@
 #include <waiting_threads.h>
 #include <m_string.h>
 
-/*
-  status variables:
-    distribution of cycle lengths
-    wait time log distribution
-
-  Note:
+/* status variables */
 
-    we call deadlock() twice per wait (with different search lengths).
-    it means a deadlock will be counted twice. It's difficult to avoid,
-    as on the second search we could find a *different* deadlock and we
-    *want* to count it too. So we just count all deadlocks - two searches
-    mean two increments on the wt_cycle_stats.
+/**
+  preset table of wait intervals
 */
-
 ulonglong wt_wait_table[WT_WAIT_STATS];
+/**
+  wait time distribution (log e scale)
+*/
 uint32 wt_wait_stats[WT_WAIT_STATS+1];
-uint32    wt_cycle_stats[2][WT_CYCLE_STATS+1], wt_success_stats;
+/**
+  distribution of cycle lengths
+  first column tells whether this was during short or long detection
+*/
+uint32 wt_cycle_stats[2][WT_CYCLE_STATS+1];
+uint32 wt_success_stats;
 
 static my_atomic_rwlock_t cycle_stats_lock, wait_stats_lock, success_stats_lock;
 
+#ifdef SAFE_STATISTICS
+#define incr(VAR, LOCK)                           \
+  do {                                            \
+    my_atomic_rwlock_wrlock(&(LOCK));             \
+    my_atomic_add32(&(VAR), 1);                   \
+    my_atomic_rwlock_wrunlock(&(LOCK));           \
+  } while(0)
+#else
+#define incr(VAR,LOCK)  do { (VAR)++; } while(0)
+#endif
+
 static void increment_success_stats()
 {
-  my_atomic_rwlock_wrlock(&success_stats_lock);
-  my_atomic_add32(&wt_success_stats, 1);
-  my_atomic_rwlock_wrunlock(&success_stats_lock);
+  incr(wt_success_stats, success_stats_lock);
 }
 
 static void increment_cycle_stats(uint depth, uint slot)
 {
   if (depth >= WT_CYCLE_STATS)
     depth= WT_CYCLE_STATS;
-  my_atomic_rwlock_wrlock(&cycle_stats_lock);
-  my_atomic_add32(&wt_cycle_stats[slot][depth], 1);
-  my_atomic_rwlock_wrunlock(&cycle_stats_lock);
+  incr(wt_cycle_stats[slot][depth], cycle_stats_lock);
 }
 
 static void increment_wait_stats(ulonglong waited,int ret)
@@ -155,12 +222,89 @@ static void increment_wait_stats(ulonglong waited,int ret)
   if ((ret) == ETIMEDOUT)
     i= WT_WAIT_STATS;
   else
-    for (i=0; i < WT_WAIT_STATS && waited/10 > wt_wait_table[i]; i++) ;
-  my_atomic_rwlock_wrlock(&wait_stats_lock);
-  my_atomic_add32(wt_wait_stats+i, 1);
-  my_atomic_rwlock_wrunlock(&wait_stats_lock);
+    for (i= 0; i < WT_WAIT_STATS && waited/10 > wt_wait_table[i]; i++) ;
+  incr(wt_wait_stats[i], wait_stats_lock);
 }
 
+/*
+  'lock' protects 'owners', 'state', and 'waiter_count'
+  'id' is read-only
+
+  a resource is picked up from a hash in a lock-free manner
+  it's returned pinned, so it cannot be freed at once
+  but it may be freed right after the pin is removed
+  to free a resource it should
+    1. have no owners
+    2. have no waiters
+
+  two ways to access a resource:
+    1. find it in a hash
+       - it's returned pinned.
+        a) take a lock in exclusive mode
+        b) check the state, it should be ACTIVE to be usable
+        c) unpin
+    2. by a direct reference
+       - could only used if a resource cannot be freed
+       e.g. accessing a resource by thd->waiting_for is safe,
+       a resource cannot be freed as there's a thread waiting for it
+*/
+struct st_wt_resource {
+  WT_RESOURCE_ID  id;
+  uint            waiter_count;
+  enum { ACTIVE, FREE } state;
+#ifndef DBUG_OFF
+  pthread_mutex_t  *cond_mutex; /* a mutex for the 'cond' below */
+#endif
+  /*
+    before the 'lock' all elements are mutable, after (and including) -
+    immutable in the sense that lf_hash_insert() won't memcpy() over them.
+    See wt_init().
+  */
+#ifdef WT_RWLOCKS_USE_MUTEXES
+  /*
+    we need a special rwlock-like 'lock' to allow readers bypass
+    waiting writers, otherwise readers can deadlock. For example:
+
+      A waits on resource x, owned by B, B waits on resource y, owned
+      by A, we have a cycle (A->x->B->y->A)
+      Both A and B start deadlock detection:
+
+        A locks x                          B locks y
+        A goes deeper                      B goes deeper
+        A locks y                          B locks x
+
+      with mutexes it would deadlock. With rwlocks it won't, as long
+      as both A and B are taking read locks (and they do).
+      But other threads may take write locks. Assume there's
+      C who wants to start waiting on x, and D who wants to start
+      waiting on y.
+
+        A read-locks x                       B read-locks y
+        A goes deeper                        B goes deeper
+     => C write-locks x (to add a new edge)  D write-locks y
+     .. C is blocked                         D is blocked
+        A read-locks y                       B read-locks x
+
+      Now, if a read lock can bypass a pending wrote lock request, we're fine.
+      If it can not, we have a deadlock.
+
+    writer starvation is technically possible, but unlikely, because
+    the contention is expected to be low.
+  */
+  struct {
+    pthread_cond_t   cond;
+    pthread_mutex_t  mutex;
+    uint readers: 16;
+    uint pending_writers: 15;
+    uint write_locked: 1;
+  } lock;
+#else
+  rw_lock_t lock;
+#endif
+  pthread_cond_t   cond; /* the corresponding mutex is provided by the caller */
+  DYNAMIC_ARRAY    owners;
+};
+
 #ifdef  WT_RWLOCKS_USE_MUTEXES
 static void rc_rwlock_init(WT_RESOURCE *rc)
 {
@@ -169,6 +313,8 @@ static void rc_rwlock_init(WT_RESOURCE *rc)
 }
 static void rc_rwlock_destroy(WT_RESOURCE *rc)
 {
+  DBUG_ASSERT(rc->lock.write_locked == 0);
+  DBUG_ASSERT(rc->lock.readers == 0);
   pthread_cond_destroy(&rc->lock.cond);
   pthread_mutex_destroy(&rc->lock.mutex);
 }
@@ -188,7 +334,7 @@ static void rc_wrlock(WT_RESOURCE *rc)
   pthread_mutex_lock(&rc->lock.mutex);
   while (rc->lock.write_locked || rc->lock.readers)
     pthread_cond_wait(&rc->lock.cond, &rc->lock.mutex);
-  rc->lock.write_locked=1;
+  rc->lock.write_locked= 1;
   pthread_mutex_unlock(&rc->lock.mutex);
   DBUG_PRINT("wt", ("LOCK resid=%ld for WRITE", (ulong)rc->id.value));
 }
@@ -198,7 +344,7 @@ static void rc_unlock(WT_RESOURCE *rc)
   pthread_mutex_lock(&rc->lock.mutex);
   if (rc->lock.write_locked)
   {
-    rc->lock.write_locked=0;
+    rc->lock.write_locked= 0;
     pthread_cond_broadcast(&rc->lock.cond);
   }
   else if (--rc->lock.readers == 0)
@@ -242,12 +388,12 @@ static LF_HASH      reshash;
 /**
   WT_RESOURCE constructor
 
-  It's called from lf_hash and takes an offset to LF_SLIST instance.
+  It's called from lf_hash and takes a pointer to an LF_SLIST instance.
   WT_RESOURCE is located at arg+sizeof(LF_SLIST)
 */
 static void wt_resource_init(uchar *arg)
 {
-  WT_RESOURCE *rc=(WT_RESOURCE*)(arg+LF_HASH_OVERHEAD);
+  WT_RESOURCE *rc= (WT_RESOURCE*)(arg+LF_HASH_OVERHEAD);
   DBUG_ENTER("wt_resource_init");
 
   bzero(rc, sizeof(*rc));
@@ -260,12 +406,12 @@ static void wt_resource_init(uchar *arg)
 /**
   WT_RESOURCE destructor
 
-  It's called from lf_hash and takes an offset to LF_SLIST instance.
+  It's called from lf_hash and takes a pointer to an LF_SLIST instance.
   WT_RESOURCE is located at arg+sizeof(LF_SLIST)
 */
 static void wt_resource_destroy(uchar *arg)
 {
-  WT_RESOURCE *rc=(WT_RESOURCE*)(arg+LF_HASH_OVERHEAD);
+  WT_RESOURCE *rc= (WT_RESOURCE*)(arg+LF_HASH_OVERHEAD);
   DBUG_ENTER("wt_resource_destroy");
 
   DBUG_ASSERT(rc->owners.elements == 0);
@@ -278,6 +424,7 @@ static void wt_resource_destroy(uchar *arg)
 void wt_init()
 {
   DBUG_ENTER("wt_init");
+  DBUG_ASSERT(reshash.alloc.constructor != wt_resource_init);
 
   lf_hash_init(&reshash, sizeof(WT_RESOURCE), LF_HASH_UNIQUE, 0,
                sizeof_WT_RESOURCE_ID, 0, 0);
@@ -293,15 +440,15 @@ void wt_init()
   reshash.element_size= offsetof(WT_RESOURCE, lock);
   bzero(wt_wait_stats, sizeof(wt_wait_stats));
   bzero(wt_cycle_stats, sizeof(wt_cycle_stats));
-  wt_success_stats=0;
-  { /* initialize wt_wait_table[]. from 1 us to 1 min, log scale */
+  wt_success_stats= 0;
+  { /* initialize wt_wait_table[]. from 1 us to 1 min, log e scale */
     int i;
-    double from=log(1);   /* 1 us */
-    double to=log(60e6);  /* 1 min */
-    for (i=0; i < WT_WAIT_STATS; i++)
+    double from= log(1);   /* 1 us */
+    double to= log(60e6);  /* 1 min */
+    for (i= 0; i < WT_WAIT_STATS; i++)
     {
-      wt_wait_table[i]=(ulonglong)exp((to-from)/(WT_WAIT_STATS-1)*i+from);
-      DBUG_ASSERT(i==0 || wt_wait_table[i-1] != wt_wait_table[i]);
+      wt_wait_table[i]= (ulonglong)exp((to-from)/(WT_WAIT_STATS-1)*i+from);
+      DBUG_ASSERT(i == 0 || wt_wait_table[i-1] != wt_wait_table[i]);
     }
   }
   my_atomic_rwlock_init(&cycle_stats_lock);
@@ -325,7 +472,7 @@ void wt_end()
 /**
   Lazy WT_THD initialization
 
-  Cheap initialization of WT_THD. Only initialized fields that don't require
+  Cheap initialization of WT_THD. Only initialize fields that don't require
   memory allocations - basically, it only does assignments. The rest of the
   WT_THD structure will be initialized on demand, on the first use.
   This allows one to initialize lazily all WT_THD structures, even if some
@@ -335,14 +482,18 @@ void wt_end()
   @param ts     a pointer to deadlock timeout short value
   @param dl     a pointer to deadlock search depth long value
   @param tl     a pointer to deadlock timeout long value
+
+  @note these are pointers to values, and WT_THD stores them as pointers.
+  It allows one later to change search depths and timeouts for existing
+  threads. It also means that the pointers must stay valid for the lifetime
+  of WT_THD.
 */
-void wt_thd_lazy_init(WT_THD *thd, ulong *ds, ulong *ts, ulong *dl, ulong *tl)
+void wt_thd_lazy_init(WT_THD *thd, const ulong *ds, const ulong *ts,
+                                   const ulong *dl, const ulong *tl)
 {
   DBUG_ENTER("wt_thd_lazy_init");
-  thd->waiting_for=0;
-  thd->my_resources.buffer= 0;
-  thd->my_resources.elements= 0;
-  thd->weight=0;
+  thd->waiting_for= 0;
+  thd->weight= 0;
   thd->deadlock_search_depth_short= ds;
   thd->timeout_short= ts;
   thd->deadlock_search_depth_long= dl;
@@ -350,7 +501,7 @@ void wt_thd_lazy_init(WT_THD *thd, ulong *ds, ulong *ts, ulong *dl, ulong *tl)
   /* dynamic array is also initialized lazily - without memory allocations */
   my_init_dynamic_array(&thd->my_resources, sizeof(WT_RESOURCE *), 0, 5);
 #ifndef DBUG_OFF
-  thd->name=my_thread_name();
+  thd->name= my_thread_name();
 #endif
   DBUG_VOID_RETURN;
 }
@@ -367,9 +518,9 @@ static int fix_thd_pins(WT_THD *thd)
 {
   if (unlikely(thd->pins == 0))
   {
-    thd->pins=lf_hash_get_pins(&reshash);
+    thd->pins= lf_hash_get_pins(&reshash);
 #ifndef DBUG_OFF
-    thd->name=my_thread_name();
+    thd->name= my_thread_name();
 #endif
   }
   return thd->pins == 0;
@@ -380,12 +531,12 @@ void wt_thd_destroy(WT_THD *thd)
   DBUG_ENTER("wt_thd_destroy");
 
   DBUG_ASSERT(thd->my_resources.elements == 0);
+  DBUG_ASSERT(thd->waiting_for == 0);
 
   if (thd->pins != 0)
     lf_hash_put_pins(thd->pins);
 
   delete_dynamic(&thd->my_resources);
-  thd->waiting_for=0;
   DBUG_VOID_RETURN;
 }
 /**
@@ -394,7 +545,7 @@ void wt_thd_destroy(WT_THD *thd)
   It can be used in WT_RESOURCE_TYPE structures where bytewise
   comparison of values is sufficient.
 */
-int wt_resource_id_memcmp(void *a, void *b)
+int wt_resource_id_memcmp(const void *a, const void *b)
 {
   /* we use the fact that there's no padding in the middle of WT_RESOURCE_ID */
   compile_time_assert(offsetof(WT_RESOURCE_ID, type) == sizeof(ulonglong));
@@ -405,10 +556,10 @@ int wt_resource_id_memcmp(void *a, void *b)
   arguments for the recursive deadlock_search function
 */
 struct deadlock_arg {
-  WT_THD *thd;          /**< starting point of a search */
-  uint    max_depth;    /**< search depth limit */
+  WT_THD * const thd;          /**< starting point of a search */
+  uint const max_depth;        /**< search depth limit */
   WT_THD *victim;              /**< a thread to be killed to resolve a deadlock */
-  WT_RESOURCE *rc;      /**< see comment at the end of deadlock_search() */
+  WT_RESOURCE *last_locked_rc; /**< see comment at the end of deadlock_search() */
 };
 
 /**
@@ -421,10 +572,10 @@ static void change_victim(WT_THD* found, struct deadlock_arg *arg)
     if (arg->victim != arg->thd)
     {
       rc_unlock(arg->victim->waiting_for); /* release the previous victim */
-      DBUG_ASSERT(arg->rc == found->waiting_for);
+      DBUG_ASSERT(arg->last_locked_rc == found->waiting_for);
     }
     arg->victim= found;
-    arg->rc= 0;
+    arg->last_locked_rc= 0;
   }
 }
 
@@ -444,7 +595,7 @@ static int deadlock_search(struct deadlock_arg *arg, WT_THD *blocker,
 
   LF_REQUIRE_PINS(1);
 
-  arg->rc= 0;
+  arg->last_locked_rc= 0;
 
   if (depth > arg->max_depth)
   {
@@ -453,7 +604,10 @@ static int deadlock_search(struct deadlock_arg *arg, WT_THD *blocker,
   }
 
 retry:
-  /* safe dereference as explained in lf_alloc-pin.c */
+  /*
+    safe dereference as explained in lf_alloc-pin.c
+    (in short: protects against lf_alloc_free() in lf_hash_delete())
+  */
   do
   {
     rc= *shared_ptr;
@@ -469,6 +623,7 @@ static int deadlock_search(struct deadlock_arg *arg, WT_THD *blocker,
   rc_rdlock(rc);
   if (rc->state != ACTIVE || *shared_ptr != rc)
   {
+    /* blocker is not waiting on this resource anymore */
     rc_unlock(rc);
     lf_unpin(arg->thd->pins, 0);
     goto retry;
@@ -480,20 +635,22 @@ static int deadlock_search(struct deadlock_arg *arg, WT_THD *blocker,
     Below is not a pure depth-first search. It's a depth-first with a
     slightest hint of breadth-first. Depth-first is:
 
-      check(element):
+      check(element, X):
         foreach current in element->nodes[] do:
-          if current == element return error;
-          check(current);
+          if current == X return error;
+          check(current, X);
 
     while we do
 
-      check(element):
+      check(element, X):
         foreach current in element->nodes[] do:
-          if current == element return error;
+          if current == X return error;
         foreach current in element->nodes[] do:
-          check(current);
+          check(current, X);
+
+    preferring shorter deadlocks over longer ones.
   */
-  for (i=0; i < rc->owners.elements; i++)
+  for (i= 0; i < rc->owners.elements; i++)
   {
     cursor= *dynamic_element(&rc->owners, i, WT_THD**);
     /*
@@ -517,7 +674,7 @@ static int deadlock_search(struct deadlock_arg *arg, WT_THD *blocker,
       goto end;
     }
   }
-  for (i=0; i < rc->owners.elements; i++)
+  for (i= 0; i < rc->owners.elements; i++)
   {
     cursor= *dynamic_element(&rc->owners, i, WT_THD**);
     switch (deadlock_search(arg, cursor, depth+1)) {
@@ -528,20 +685,21 @@ static int deadlock_search(struct deadlock_arg *arg, WT_THD *blocker,
       break;
     case WT_DEADLOCK:
       ret= WT_DEADLOCK;
-      change_victim(cursor, arg);       /* also sets arg->rc to 0 */
+      change_victim(cursor, arg);       /* also sets arg->last_locked_rc to 0 */
       i= rc->owners.elements;           /* jump out of the loop */
       break;
     default:
       DBUG_ASSERT(0);
     }
-    if (arg->rc)
-      rc_unlock(arg->rc);
+    if (arg->last_locked_rc)
+      rc_unlock(arg->last_locked_rc);
   }
 end:
   /*
     Note that 'rc' is locked in this function, but it's never unlocked here.
-    Instead it's saved in arg->rc and the *caller* is expected to unlock it.
-    It's done to support different killing strategies. This is how it works:
+    Instead it's saved in arg->last_locked_rc and the *caller* is
+    expected to unlock it.  It's done to support different killing
+    strategies. This is how it works:
     Assuming a graph
 
       thd->A->B->C->thd
@@ -552,9 +710,9 @@ static int deadlock_search(struct deadlock_arg *arg, WT_THD *blocker,
     on. Goes down recursively, locks B. Goes down recursively, locks C.
     Notices that C is waiting on thd. Deadlock detected. Sets arg->victim=thd.
     Returns from the last deadlock_search() call. C stays locked!
-    Now it checks whether C is a more appropriate victim then 'thd'.
+    Now it checks whether C is a more appropriate victim than 'thd'.
     If yes - arg->victim=C, otherwise C is unlocked. Returns. B stays locked.
-    Now it checks whether B is a more appropriate victim then arg->victim.
+    Now it checks whether B is a more appropriate victim than arg->victim.
     If yes - old arg->victim is unlocked and arg->victim=B,
     otherwise B is unlocked. Return.
     And so on.
@@ -566,7 +724,7 @@ static int deadlock_search(struct deadlock_arg *arg, WT_THD *blocker,
     is unrolled and we are back to deadlock() function, there are only two
     locks left - on thd and on the victim.
   */
-  arg->rc= rc;
+  arg->last_locked_rc= rc;
   DBUG_PRINT("wt", ("exit: %s",
                     ret == WT_DEPTH_EXCEEDED ? "WT_DEPTH_EXCEEDED" :
                     ret ? "WT_DEADLOCK" : "OK"));
@@ -612,30 +770,31 @@ static int deadlock(WT_THD *thd, WT_THD *blocker, uint depth,
   */
   if (ret == WT_DEADLOCK && depth)
     change_victim(blocker, &arg);
-  if (arg.rc)
+  if (arg.last_locked_rc)
   {
     /*
       Special return code if there's nobody to wait for.
 
       depth == 0 means that we start the search from thd (thd == blocker).
-      ret == WT_OK means that no cycle was found and arg.rc == thd->waiting_for.
-      and arg.rc->owners.elements == 0 means that (applying the rule above)
-      thd->waiting_for->owners.elements == 0, and thd doesn't have anybody to
-      wait for.
+      ret == WT_OK means that no cycle was found and
+        arg.last_locked_rc == thd->waiting_for.
+      and arg.last_locked_rc->owners.elements == 0 means that
+        (applying the rule above) thd->waiting_for->owners.elements == 0,
+        and thd doesn't have anybody to wait for.
     */
-    if (depth == 0 && ret == WT_OK && arg.rc->owners.elements == 0)
+    if (depth == 0 && ret == WT_OK && arg.last_locked_rc->owners.elements == 0)
     {
       DBUG_ASSERT(thd == blocker);
-      DBUG_ASSERT(arg.rc == thd->waiting_for);
+      DBUG_ASSERT(arg.last_locked_rc == thd->waiting_for);
       ret= WT_FREE_TO_GO;
     }
-    rc_unlock(arg.rc);
+    rc_unlock(arg.last_locked_rc);
   }
   /* notify the victim, if appropriate */
   if (ret == WT_DEADLOCK && arg.victim != thd)
   {
     DBUG_PRINT("wt", ("killing %s", arg.victim->name));
-    arg.victim->killed=1;
+    arg.victim->killed= 1;
     pthread_cond_broadcast(&arg.victim->waiting_for->cond);
     rc_unlock(arg.victim->waiting_for);
     ret= WT_OK;
@@ -659,7 +818,7 @@ static int unlock_lock_and_free_resource(WT_THD *thd, WT_RESOURCE *rc)
 
   if (rc->owners.elements || rc->waiter_count)
   {
-    DBUG_PRINT("wt", ("nothing to do, %d owners, %d waiters",
+    DBUG_PRINT("wt", ("nothing to do, %u owners, %u waiters",
                       rc->owners.elements, rc->waiter_count));
     rc_unlock(rc);
     DBUG_RETURN(0);
@@ -683,12 +842,8 @@ static int unlock_lock_and_free_resource(WT_THD *thd, WT_RESOURCE *rc)
      2. set the state to FREE
      3. release the lock
      4. remove from the hash
-
-     I *think* it's safe to release the lock while the element is still
-     in the hash. If not, the corrected procedure should be
-     3. pin; 4; remove; 5; release; 6; unpin and it'll need pin[3].
   */
-  rc->state=FREE;
+  rc->state= FREE;
   rc_unlock(rc);
   DBUG_RETURN(lf_hash_delete(&reshash, thd->pins, key, keylen) == -1);
 }
@@ -739,15 +894,19 @@ static int stop_waiting(WT_THD *thd)
 /**
   notify the system that a thread needs to wait for another thread
 
-  called by a *waiter* to declare what resource it will wait for.
+  called by a *waiter* to declare that it (thd) will wait for another
+  thread (blocker) on a specific resource (resid).
   can be called many times, if many blockers own a blocking resource.
   but must always be called with the same resource id - a thread cannot
   wait for more than one resource at a time.
 
+  @return WT_OK or WT_DEADLOCK
+
   As a new edge is added to the wait-for graph, a deadlock detection is
   performed for this new edge.
 */
-int wt_thd_will_wait_for(WT_THD *thd, WT_THD *blocker, WT_RESOURCE_ID *resid)
+int wt_thd_will_wait_for(WT_THD *thd, WT_THD *blocker,
+                         const WT_RESOURCE_ID *resid)
 {
   uint i;
   WT_RESOURCE *rc;
@@ -822,7 +981,7 @@ int wt_thd_will_wait_for(WT_THD *thd, WT_THD *blocker, WT_RESOURCE_ID *resid)
 
     /*
       we can safely access the resource here, it's in the hash as it has
-      at least one owner, and non-zero waiter_count
+      non-zero waiter_count
     */
     rc= thd->waiting_for;
     rc_wrlock(rc);
@@ -835,7 +994,11 @@ int wt_thd_will_wait_for(WT_THD *thd, WT_THD *blocker, WT_RESOURCE_ID *resid)
       DBUG_RETURN(WT_DEADLOCK);
     }
   }
-  for (i=0; i < rc->owners.elements; i++)
+  /*
+    Another thread could be waiting on this resource for this very 'blocker'.
+    In this case we should not add it to the list for the second time.
+  */
+  for (i= 0; i < rc->owners.elements; i++)
     if (*dynamic_element(&rc->owners, i, WT_THD**) == blocker)
       break;
   if (i >= rc->owners.elements)
@@ -854,19 +1017,21 @@ int wt_thd_will_wait_for(WT_THD *thd, WT_THD *blocker, WT_RESOURCE_ID *resid)
   }
   rc_unlock(rc);
 
-  if (deadlock(thd, blocker, 1, *thd->deadlock_search_depth_short))
+  if (deadlock(thd, blocker, 1, *thd->deadlock_search_depth_short) != WT_OK)
   {
     stop_waiting(thd);
     DBUG_RETURN(WT_DEADLOCK);
   }
-  DBUG_RETURN(0);
+  DBUG_RETURN(WT_OK);
 }
 
 /**
-  called by a *waiter* to start waiting
+  called by a *waiter* (thd) to start waiting
 
   It's supposed to be a drop-in replacement for
   pthread_cond_timedwait(), and it takes mutex as an argument.
+
+  @return one of WT_TIMEOUT, WT_DEADLOCK, WT_OK
 */
 int wt_thd_cond_timedwait(WT_THD *thd, pthread_mutex_t *mutex)
 {
@@ -878,10 +1043,10 @@ int wt_thd_cond_timedwait(WT_THD *thd, pthread_mutex_t *mutex)
   DBUG_PRINT("wt", ("enter: thd=%s, rc=%p", thd->name, rc));
 
 #ifndef DBUG_OFF
-  if (rc->mutex)
-    DBUG_ASSERT(rc->mutex == mutex);
+  if (rc->cond_mutex)
+    DBUG_ASSERT(rc->cond_mutex == mutex);
   else
-    rc->mutex= mutex;
+    rc->cond_mutex= mutex;
   safe_mutex_assert_owner(mutex);
 #endif
 
@@ -890,20 +1055,27 @@ int wt_thd_cond_timedwait(WT_THD *thd, pthread_mutex_t *mutex)
 #ifdef __WIN__
   /*
     only for the sake of Windows we distinguish between
-    'before' and 'starttime'
+    'before' and 'starttime':
+
+    my_getsystime() returns high-resolution value, that cannot be used for
+    waiting (it doesn't follow system clock changes), but is good for time
+    intervals.
+
+    GetSystemTimeAsFileTime() follows system clock, but is low-resolution
+    and will result in lousy intervals.
   */
   GetSystemTimeAsFileTime((PFILETIME)&starttime);
 #endif
 
   rc_wrlock(rc);
-  if (rc->owners.elements == 0 || thd->killed)
+  if (rc->owners.elements == 0)
     ret= WT_OK;
   rc_unlock(rc);
 
   set_timespec_time_nsec(timeout, starttime, (*thd->timeout_short)*ULL(1000));
-  if (ret == WT_TIMEOUT)
+  if (ret == WT_TIMEOUT && !thd->killed)
     ret= pthread_cond_timedwait(&rc->cond, mutex, &timeout);
-  if (ret == WT_TIMEOUT)
+  if (ret == WT_TIMEOUT && !thd->killed)
   {
     int r= deadlock(thd, thd, 0, *thd->deadlock_search_depth_long);
     if (r == WT_FREE_TO_GO)
@@ -935,24 +1107,25 @@ int wt_thd_cond_timedwait(WT_THD *thd, pthread_mutex_t *mutex)
   @param resid   a resource to release. 0 to release all resources
 */
 
-void wt_thd_release(WT_THD *thd, WT_RESOURCE_ID *resid)
+void wt_thd_release(WT_THD *thd, const WT_RESOURCE_ID *resid)
 {
   uint i;
   DBUG_ENTER("wt_thd_release");
 
-  for (i=0; i < thd->my_resources.elements; i++)
+  for (i= 0; i < thd->my_resources.elements; i++)
   {
-    uint j;
     WT_RESOURCE *rc= *dynamic_element(&thd->my_resources, i, WT_RESOURCE**);
     if (!resid || (resid->type->compare(&rc->id, resid) == 0))
     {
+      uint j;
+
       rc_wrlock(rc);
       /*
         nobody's trying to free the resource now,
         as its owners[] array is not empty (at least thd must be there)
       */
       DBUG_ASSERT(rc->state == ACTIVE);
-      for (j=0; j < rc->owners.elements; j++)
+      for (j= 0; j < rc->owners.elements; j++)
         if (*dynamic_element(&rc->owners, j, WT_THD**) == thd)
           break;
       DBUG_ASSERT(j < rc->owners.elements);
@@ -961,8 +1134,8 @@ void wt_thd_release(WT_THD *thd, WT_RESOURCE_ID *resid)
       {
         pthread_cond_broadcast(&rc->cond);
 #ifndef DBUG_OFF
-        if (rc->mutex)
-          safe_mutex_assert_owner(rc->mutex);
+        if (rc->cond_mutex)
+          safe_mutex_assert_owner(rc->cond_mutex);
 #endif
       }
       unlock_lock_and_free_resource(thd, rc);

server-tools/instance-manager/parse.cc

@@ -78,7 +78,7 @@ Named_value_arr::Named_value_arr() :
 
 bool Named_value_arr::init()
 {
-  if (my_init_dynamic_array(&arr, sizeof(Named_value), 0, 32))
+  if (my_init_dynamic_array(&arr, sizeof(Named_value), 32, 32))
     return TRUE;
 
   initialized= TRUE;

sql/mysqld.cc

-/* Copyright (C) 2000-2003 MySQL AB
+/* Copyright (C) 2000-2008 MySQL AB, 2008-2009 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
@@ -3718,8 +3718,6 @@ static int init_server_components()
   if (table_cache_init() | table_def_init() | hostname_cache_init())
     unireg_abort(1);
 
-  wt_init();
-
   query_cache_result_size_limit(query_cache_limit);
   query_cache_set_min_res_unit(query_cache_min_res_unit);
   query_cache_init();
@@ -3731,6 +3729,7 @@ static int init_server_components()
 #ifdef HAVE_REPLICATION
   init_slave_list();
 #endif
+  wt_init();
 
   /* Setup logs */
 
@@ -7471,7 +7470,7 @@ static void usage(void)
     default_collation_name= (char*) default_charset_info->name;
   print_version();
   puts("\
-Copyright (C) 2000 MySQL AB, by Monty and others\n\
+Copyright (C) 2000-2008 MySQL AB, Monty and others, 2008-2009 Sun Microsystems, Inc.\n\
 This software comes with ABSOLUTELY NO WARRANTY. This is free software,\n\
 and you are welcome to modify and redistribute it under the GPL license\n\n\
 Starts the MySQL database server\n");

sql/sql_class.cc

-/* Copyright (C) 2000-2006 MySQL AB
+/* Copyright (C) 2000-2008 MySQL AB, 2008-2009 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
@@ -1123,6 +1123,8 @@ bool THD::store_globals()
   */
   mysys_var->id= thread_id;
   real_id= pthread_self();                      // For debugging
+  mysys_var->stack_ends_here= thread_stack +    // for consistency, see libevent_thread_proc
+                              STACK_DIRECTION * (long)my_thread_stack_size;
 
   /*
     We have to call thr_lock_info_init() again here as THD may have been

sql/sql_class.h

-/* Copyright (C) 2000-2006 MySQL AB
+/* Copyright (C) 2000-2008 MySQL AB, 2008-2009 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
@@ -1417,7 +1417,7 @@ class THD :public Statement,
     THD_TRANS stmt;			// Trans for current statement
     bool on;                            // see ha_enable_transaction()
     XID_STATE xid_state;
-    WT_THD wt;
+    WT_THD wt;                          ///< for deadlock detection
     Rows_log_event *m_pending_rows_event;
 
     /*

storage/maria/ha_maria.cc

-/* Copyright (C) 2006,2004 MySQL AB & MySQL Finland AB & TCX DataKonsult AB
+/* Copyright (C) 2004-2008 MySQL AB & MySQL Finland AB & TCX DataKonsult AB
+   Copyright (C) 2008-2009 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
@@ -40,9 +41,11 @@ C_MODE_END
   Note that in future versions, only *transactional* Maria tables can
   rollback, so this flag should be up or down conditionally.
 */
-#define MARIA_CANNOT_ROLLBACK HA_NO_TRANSACTIONS
 #ifdef MARIA_CANNOT_ROLLBACK
+#define CANNOT_ROLLBACK_FLAG HA_NO_TRANSACTIONS
 #define trans_register_ha(A, B, C)  do { /* nothing */ } while(0)
+#else
+#define CANNOT_ROLLBACK_FLAG 0
 #endif
 #define THD_TRN (*(TRN **)thd_ha_data(thd, maria_hton))
 
@@ -716,7 +719,7 @@ handler(hton, table_arg), file(0),
 int_table_flags(HA_NULL_IN_KEY | HA_CAN_FULLTEXT | HA_CAN_SQL_HANDLER |
                 HA_BINLOG_ROW_CAPABLE | HA_BINLOG_STMT_CAPABLE |
                 HA_DUPLICATE_POS | HA_CAN_INDEX_BLOBS | HA_AUTO_PART_KEY |
-                HA_FILE_BASED | HA_CAN_GEOMETRY | MARIA_CANNOT_ROLLBACK |
+                HA_FILE_BASED | HA_CAN_GEOMETRY | CANNOT_ROLLBACK_FLAG |
                 HA_CAN_BIT_FIELD | HA_CAN_RTREEKEYS |
                 HA_HAS_RECORDS | HA_STATS_RECORDS_IS_EXACT),
 can_enable_indexes(1), bulk_insert_single_undo(BULK_INSERT_NONE)

storage/maria/ma_commit.c

-/* Copyright (C) 2007 MySQL AB
+/* Copyright (C) 2007-2008 MySQL AB, 2008-2009 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
@@ -17,7 +17,7 @@
 #include "trnman.h"
 
 /**
-   @brief writes a COMMIT record to log and commits transaction in memory
+   writes a COMMIT record to log and commits transaction in memory
 
    @param  trn              transaction
 
@@ -82,7 +82,7 @@ int ma_commit(TRN *trn)
 
 
 /**
-   @brief Writes a COMMIT record for a transaciton associated with a file
+   Writes a COMMIT record for a transaciton associated with a file
 
    @param  info              Maria handler
 
@@ -98,13 +98,17 @@ int maria_commit(MARIA_HA *info)
 
 
 /**
-   @brief Starts a transaction on a file handle
+   Starts a transaction on a file handle
 
    @param  info              Maria handler
 
    @return Operation status
      @retval 0      ok
      @retval #      Error code.
+
+   @note this can be used only in single-threaded programs (tests),
+   because we create a transaction (trnman_new_trn) with WT_THD=0.
+   XXX it needs to be fixed when we'll start using maria_begin from SQL.
 */
 
 int maria_begin(MARIA_HA *info)

storage/maria/ma_write.c

-/* Copyright (C) 2006 MySQL AB & MySQL Finland AB & TCX DataKonsult AB
+/* Copyright (C) 2004-2008 MySQL AB & MySQL Finland AB & TCX DataKonsult AB
+   Copyright (C) 2008-2009 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
@@ -39,8 +40,8 @@ static uchar *_ma_find_last_pos(MARIA_HA *info, MARIA_KEY *int_key,
                                 uchar *page, uchar **after_key);
 static my_bool _ma_ck_write_tree(register MARIA_HA *info, MARIA_KEY *key);
 static my_bool _ma_ck_write_btree(register MARIA_HA *info, MARIA_KEY *key);
-static int _ma_ck_write_btree_with_log(MARIA_HA *info, MARIA_KEY *key,
-                                       my_off_t *root, uint32 comp_flag);
+static int _ma_ck_write_btree_with_log(MARIA_HA *, MARIA_KEY *, my_off_t *,
+                                       uint32);
 static my_bool _ma_log_split(MARIA_HA *info, my_off_t page, const uchar *buff,
                              uint org_length, uint new_length,
                              const uchar *key_pos,
@@ -181,9 +182,8 @@ int maria_write(MARIA_HA *info, uchar *record)
       else
       {
         while (keyinfo->ck_insert(info,
-                                  (*keyinfo->make_key)(info, &int_key, i,
-                                                       buff, record, filepos,
-                                                       info->trn->trid)))
+                 (*keyinfo->make_key)(info, &int_key, i, buff, record,
+                                      filepos, info->trn->trid)))
         {
           TRN *blocker;
           DBUG_PRINT("error",("Got error: %d on write",my_errno));
@@ -193,10 +193,12 @@ int maria_write(MARIA_HA *info, uchar *record)
             below doesn't work for them.
             Also, filter out non-thread maria use, and table modified in
             the same transaction.
+            At last, filter out non-dup-unique errors.
           */
           if (!local_lock_tree)
             goto err;
-          if (info->dup_key_trid == info->trn->trid)
+          if (info->dup_key_trid == info->trn->trid ||
+              my_errno != HA_ERR_FOUND_DUPP_KEY)
           {
 	    rw_unlock(&keyinfo->root_lock);
             goto err;
@@ -257,6 +259,9 @@ int maria_write(MARIA_HA *info, uchar *record)
             }
           }
           rw_wrlock(&keyinfo->root_lock);
+#ifndef MARIA_CANNOT_ROLLBACK
+          keyinfo->version++;
+#endif
         }
       }
 
@@ -671,12 +676,14 @@ static int w_search(register MARIA_HA *info, uint32 comp_flag, MARIA_KEY *key,
         When the index will support true versioning - with multiple
         identical values in the UNIQUE index, invisible to each other -
         the following should be changed to "continue inserting keys, at the
-        end (of the row or statement) wait". Until it's done we cannot properly
-        support deadlock timeouts.
+        end (of the row or statement) wait". We need to wait on *all*
+        unique conflicts at once, not one-at-a-time, because we need to
+        know all blockers in advance, otherwise we'll have incomplete wait-for
+        graph.
       */
       /*
-        transaction that has inserted the conflicting key is in progress.
-        wait for it to be committed or aborted.
+        transaction that has inserted the conflicting key may be in progress.
+        the caller will wait for it to be committed or aborted.
       */
       info->dup_key_trid= _ma_trid_from_key(&tmp_key);
       info->dup_key_pos= dup_key_pos;

storage/maria/trnman.c

-/* Copyright (C) 2006 MySQL AB
+/* Copyright (C) 2006-2008 MySQL AB, 2008-2009 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
@@ -42,7 +42,7 @@ static TrID global_trid_generator;
   The default value is used when transaction manager not initialize;
   Probably called from maria_chk
 */
-static TrID trid_min_read_from= ~(TrID) 0;
+static TrID trid_min_read_from= MAX_TRID;
 
 /* the mutex for everything above */
 static pthread_mutex_t LOCK_trn_list;
@@ -59,6 +59,7 @@ static TRN **short_trid_to_active_trn;
 /* locks for short_trid_to_active_trn and pool */
 static my_atomic_rwlock_t LOCK_short_trid_to_trn, LOCK_pool;
 static my_bool default_trnman_end_trans_hook(TRN *, my_bool, my_bool);
+static void trnman_free_trn(TRN *);
 
 my_bool (*trnman_end_trans_hook)(TRN *, my_bool, my_bool)=
   default_trnman_end_trans_hook;
@@ -88,6 +89,7 @@ void trnman_reset_locked_tables(TRN *trn, uint locked_tables)
   trn->locked_tables= locked_tables;
 }
 
+/** Wake up threads waiting for this transaction */
 static void wt_thd_release_self(TRN *trn)
 {
   if (trn->wt)
@@ -149,12 +151,12 @@ int trnman_init(TrID initial_trid)
   */
 
   active_list_max.trid= active_list_min.trid= 0;
-  active_list_max.min_read_from= ~(TrID) 0;
+  active_list_max.min_read_from= MAX_TRID;
   active_list_max.next= active_list_min.prev= 0;
   active_list_max.prev= &active_list_min;
   active_list_min.next= &active_list_max;
 
-  committed_list_max.commit_trid= ~(TrID) 0;
+  committed_list_max.commit_trid= MAX_TRID;
   committed_list_max.next= committed_list_min.prev= 0;
   committed_list_max.prev= &committed_list_min;
   committed_list_min.next= &committed_list_max;
@@ -198,6 +200,7 @@ void trnman_destroy()
   {
     TRN *trn= pool;
     pool= pool->next;
+    DBUG_ASSERT(trn->wt == NULL);
     pthread_mutex_destroy(&trn->state_lock);
     my_free((void *)trn, MYF(0));
   }
@@ -251,10 +254,12 @@ static uint get_short_trid(TRN *trn)
   return res;
 }
 
-/*
-  DESCRIPTION
-    start a new transaction, allocate and initialize transaction object
-    mutex and cond will be used for lock waits
+/**
+  Allocates and initialzies a new TRN object
+
+  @note the 'wt' parameter can only be 0 in a single-threaded code (or,
+  generally, where threads cannot block each other), otherwise the
+  first call to the deadlock detector will sigsegv.
 */
 
 TRN *trnman_new_trn(WT_THD *wt)
@@ -338,7 +343,8 @@ TRN *trnman_new_trn(WT_THD *wt)
     trn->min_read_from= trn->trid + 1;
   }
 
-  trn->commit_trid=  ~(TrID)0;
+  /* no other transaction can read changes done by this one */
+  trn->commit_trid=  MAX_TRID;
   trn->rec_lsn= trn->undo_lsn= trn->first_undo_lsn= 0;
   trn->used_tables= 0;
 
@@ -394,6 +400,7 @@ my_bool trnman_end_trn(TRN *trn, my_bool commit)
 
   /* if a rollback, all UNDO records should have been executed */
   DBUG_ASSERT(commit || trn->undo_lsn == 0);
+  DBUG_ASSERT(trn != &dummy_transaction_object);
   DBUG_PRINT("info", ("pthread_mutex_lock LOCK_trn_list"));
 
   pthread_mutex_lock(&LOCK_trn_list);
@@ -429,6 +436,7 @@ my_bool trnman_end_trn(TRN *trn, my_bool commit)
   }
 
   pthread_mutex_lock(&trn->state_lock);
+  if (commit)
     trn->commit_trid= global_trid_generator;
   wt_thd_release_self(trn);
   pthread_mutex_unlock(&trn->state_lock);
@@ -502,7 +510,7 @@ my_bool trnman_end_trn(TRN *trn, my_bool commit)
   running. It may even be called automatically on checkpoints if no
   transactions are running.
 */
-void trnman_free_trn(TRN *trn)
+static void trnman_free_trn(TRN *trn)
 {
   /*
      union is to solve strict aliasing issue.
@@ -580,6 +588,16 @@ int trnman_can_read_from(TRN *trn, TrID trid)
   return can;
 }
 
+/**
+  Finds a TRN by its TrID
+
+  @param trn    current trn. Needed for pinning pointers (see lf_pin)
+  @param trid   trid to search for
+
+  @return found trn or 0
+
+  @note that trn is returned with its state locked!
+*/
 TRN *trnman_trid_to_trn(TRN *trn, TrID trid)
 {
   TRN **found;
@@ -604,7 +622,7 @@ TRN *trnman_trid_to_trn(TRN *trn, TrID trid)
   lf_hash_search_unpin(trn->pins);
 
   /* Gotcha! */
-  return *found; /* note that TRN is returned locked !!! */
+  return *found;
 }
 
 /* TODO: the stubs below are waiting for savepoints to be implemented */

storage/maria/trnman.h

-/* Copyright (C) 2006 MySQL AB
+/* Copyright (C) 2006-2008 MySQL AB, 2008-2009 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
@@ -22,7 +22,7 @@ C_MODE_START
 #include "trnman_public.h"
 #include "ma_loghandler_lsn.h"
 
-/*
+/**
   trid - 6 uchar transaction identifier. Assigned when a transaction
   is created. Transaction can always be identified by its trid,
   even after transaction has ended.
@@ -33,7 +33,7 @@ C_MODE_START
   when short_id is 0, TRN is not initialized, for all practical purposes
   it could be considered unused.
 
-  when commit_trid is ~(TrID)0 the transaction is running, otherwise it's
+  when commit_trid is MAX_TRID the transaction is running, otherwise it's
   committed.
 
   state_lock mutex protects the state of a TRN, that is whether a TRN
@@ -46,7 +46,7 @@ struct st_ma_transaction
   LF_PINS              *pins;
   WT_THD               *wt;
   pthread_mutex_t      state_lock;
-  void                 *used_tables;  /* Tables used by transaction */
+  void                 *used_tables;  /**< Tables used by transaction */
   TRN                  *next, *prev;
   TrID                 trid, min_read_from, commit_trid;
   LSN		       rec_lsn, undo_lsn;
@@ -56,6 +56,7 @@ struct st_ma_transaction
 };
 
 #define TRANSACTION_LOGGED_LONG_ID ULL(0x8000000000000000)
+#define MAX_TRID (~(TrID)0)
 
 extern WT_RESOURCE_TYPE ma_rc_dup_unique;
 

storage/maria/trnman_public.h

-/* Copyright (C) 2006 MySQL AB
+/* Copyright (C) 2006-2008 MySQL AB, 2008-2009 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
@@ -44,7 +44,6 @@ my_bool trnman_end_trn(TRN *trn, my_bool commit);
 #define trnman_commit_trn(T) trnman_end_trn(T, TRUE)
 #define trnman_abort_trn(T)  trnman_end_trn(T, FALSE)
 #define trnman_rollback_trn(T)  trnman_end_trn(T, FALSE)
-void trnman_free_trn(TRN *trn);
 int trnman_can_read_from(TRN *trn, TrID trid);
 TRN *trnman_trid_to_trn(TRN *trn, TrID trid);
 void trnman_new_statement(TRN *trn);

storage/maria/unittest/trnman-t.c

-/* Copyright (C) 2006 MySQL AB
+/* Copyright (C) 2006-2008 MySQL AB, 2008-2009 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
@@ -40,7 +40,8 @@ pthread_handler_t test_trnman(void *arg)
   TRN    *trn[MAX_ITER];
   int    m= (*(int *)arg);
 
-  my_thread_init();
+  if (my_thread_init())
+    BAIL_OUT("my_thread_init failed!");
 
   for (x= ((int)(intptr)(&m)); m > 0; )
   {

unittest/mysys/lf-t.c

-/* Copyright (C) 2006 MySQL AB
+/* Copyright (C) 2008-2008 MySQL AB, 2008-2009 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
@@ -13,6 +13,12 @@
    along with this program; if not, write to the Free Software
    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA */
 
+/**
+  @file
+
+  Unit tests for lock-free algorithms of mysys
+*/
+
 #include "thr_template.c"
 
 #include <lf.h>
@@ -47,6 +53,10 @@ pthread_handler_t test_lf_pinbox(void *arg)
   return 0;
 }
 
+/*
+  thread local data area, allocated using lf_alloc.
+  union is required to enforce the minimum required element size (sizeof(ptr))
+*/
 typedef union {
   int32 data;
   void *not_used;

unittest/mysys/my_atomic-t.c

-/* Copyright (C) 2006 MySQL AB
+/* Copyright (C) 2006-2008 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

unittest/mysys/thr_template.c

-/* Copyright (C) 2006 MySQL AB
+/* Copyright (C) 2006-2008 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

unittest/mysys/waiting_threads-t.c

-/* Copyright (C) 2006 MySQL AB
+/* Copyright (C) 2008 MySQL AB, 2008-2009 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
@@ -16,7 +16,6 @@
 #include "thr_template.c"
 #include <waiting_threads.h>
 #include <m_string.h>
-#include <locale.h>
 
 struct test_wt_thd {
   WT_THD thd;
@@ -31,6 +30,7 @@ ulong wt_timeout_long=10000, wt_deadlock_search_depth_long=15;
 
 #define reset(ARRAY) bzero(ARRAY, sizeof(ARRAY))
 
+/* see explanation of the kill strategies in waiting_threads.h */
 enum { LATEST, RANDOM, YOUNGEST, LOCKS } kill_strategy;
 
 WT_RESOURCE_TYPE restype={ wt_resource_id_memcmp, 0};
@@ -68,13 +68,14 @@ pthread_handler_t test_wt(void *arg)
 
     res= 0;
 
+    /* prepare for waiting for a random number of random threads */
     for (j= n= (rnd() % THREADS)/10; !res && j >= 0; j--)
     {
 retry:
-      i= rnd() % (THREADS-1);
-      if (i >= id) i++;
+      i= rnd() % (THREADS-1); /* pick a random thread */
+      if (i >= id) i++;   /* with a number from 0 to THREADS-1 excluding ours */
 
-      for (k=n; k >=j; k--)
+      for (k=n; k >=j; k--) /* the one we didn't pick before */
         if (blockers[k] == i)
           goto retry;
       blockers[j]= i;
@@ -121,7 +122,7 @@ pthread_handler_t test_wt(void *arg)
 #define DEL "(deleted)"
     char *x=malloc(strlen(thds[id].thd.name)+sizeof(DEL)+1);
     strxmov(x, thds[id].thd.name, DEL, 0);
-    thds[id].thd.name=x; /* it's a memory leak, go on, shoot me */
+    thds[id].thd.name=x;
   }
 #endif
 
@@ -165,8 +166,8 @@ void do_one_test()
 
 void do_tests()
 {
-  plan(12);
-  compile_time_assert(THREADS >= 3);
+  plan(14);
+  compile_time_assert(THREADS >= 4);
 
   DBUG_PRINT("wt", ("================= initialization ==================="));
 
@@ -206,22 +207,22 @@ void do_tests()
     pthread_mutex_lock(&lock);
     bad= wt_thd_cond_timedwait(& thds[0].thd, &lock);
     pthread_mutex_unlock(&lock);
-    ok(bad == ETIMEDOUT, "timeout test returned %d", bad);
+    ok(bad == WT_TIMEOUT, "timeout test returned %d", bad);
 
     ok_wait(0,1,0);
     ok_wait(1,2,1);
     ok_deadlock(2,0,2);
 
     pthread_mutex_lock(&lock);
-    wt_thd_cond_timedwait(& thds[0].thd, &lock);
-    wt_thd_cond_timedwait(& thds[1].thd, &lock);
+    ok(wt_thd_cond_timedwait(& thds[0].thd, &lock) == WT_TIMEOUT, "as always");
+    ok(wt_thd_cond_timedwait(& thds[1].thd, &lock) == WT_TIMEOUT, "as always");
     wt_thd_release_all(& thds[0].thd);
     wt_thd_release_all(& thds[1].thd);
     wt_thd_release_all(& thds[2].thd);
     wt_thd_release_all(& thds[3].thd);
     pthread_mutex_unlock(&lock);
 
-    for (cnt=0; cnt < 3; cnt++)
+    for (cnt=0; cnt < 4; cnt++)
     {
       wt_thd_destroy(& thds[cnt].thd);
       wt_thd_lazy_init(& thds[cnt].thd,
@@ -261,6 +262,7 @@ void do_tests()
     wt_thd_release_all(& thds[cnt].thd);
     wt_thd_destroy(& thds[cnt].thd);
     pthread_mutex_destroy(& thds[cnt].lock);
+    free(thds[cnt].thd.name);
   }
   pthread_mutex_unlock(&lock);
   wt_end();