diff --git a/libraries/liblmdb/mdb.c b/libraries/liblmdb/mdb.c
index 6997ae9..609eb92 100644
--- a/libraries/liblmdb/mdb.c
+++ b/libraries/liblmdb/mdb.c
@@ -177,6 +177,7 @@
 #define THREAD_RET	DWORD
 #define pthread_t	HANDLE
 #define pthread_mutex_t	HANDLE
+#define pthread_cond_t	HANDLE
 #define pthread_key_t	DWORD
 #define pthread_self()	GetCurrentThreadId()
 #define pthread_key_create(x,y)	\
@@ -186,6 +187,8 @@
 #define pthread_setspecific(x,y)	(TlsSetValue(x,y) ? 0 : ErrCode())
 #define pthread_mutex_unlock(x)	ReleaseMutex(x)
 #define pthread_mutex_lock(x)	WaitForSingleObject(x, INFINITE)
+#define pthread_cond_signal(x)	SetEvent(*x)
+#define pthread_cond_wait(cond,mutex)	SignalObjectAndWait(*mutex, *cond, INFINITE, FALSE); WaitForSingleObject(*mutex, INFINITE)
 #define THREAD_CREATE(thr,start,arg)	thr=CreateThread(NULL,0,start,arg,0,NULL)
 #define THREAD_FINISH(thr)	WaitForSingleObject(thr, INFINITE)
 #define LOCK_MUTEX_R(env)	pthread_mutex_lock((env)->me_rmutex)
@@ -8034,7 +8037,8 @@ mdb_put(MDB_txn *txn, MDB_dbi dbi,
 #endif
 
 typedef struct mdb_copy {
-	pthread_mutex_t mc_mutex[2];
+	pthread_mutex_t mc_mutex;
+	pthread_cond_t mc_cond;
 	char *mc_wbuf[2];
 	char *mc_over[2];
 	MDB_env *mc_env;
@@ -8044,6 +8048,7 @@ typedef struct mdb_copy {
 	pgno_t mc_next_pgno;
 	HANDLE mc_fd;
 	int mc_status;
+	volatile int mc_new;
 	int mc_toggle;
 } mdb_copy;
 
@@ -8061,14 +8066,17 @@ mdb_env_copythr(void *arg)
 #define DO_WRITE(rc, fd, ptr, w2, len)	len = write(fd, ptr, w2); rc = (len >= 0)
 #endif
 
-	pthread_mutex_lock(&my->mc_mutex[toggle^1]);
+	pthread_mutex_lock(&my->mc_mutex);
+	my->mc_new = 0;
+	pthread_cond_signal(&my->mc_cond);
 	for(;;) {
-		pthread_mutex_lock(&my->mc_mutex[toggle]);
-		pthread_mutex_unlock(&my->mc_mutex[toggle^1]);
-		if (!my->mc_wlen[toggle]) {
-			pthread_mutex_unlock(&my->mc_mutex[toggle]);
+		while (!my->mc_new)
+			pthread_cond_wait(&my->mc_cond, &my->mc_mutex);
+		if (my->mc_new < 0) {
+			my->mc_new = 0;
 			break;
 		}
+		my->mc_new = 0;
 		wsize = my->mc_wlen[toggle];
 		ptr = my->mc_wbuf[toggle];
 again:
@@ -8089,7 +8097,6 @@ again:
 		}
 		if (rc) {
 			my->mc_status = rc;
-			pthread_mutex_unlock(&my->mc_mutex[toggle]);
 			break;
 		}
 		/* If there's an overflow page tail, write it too */
@@ -8101,23 +8108,29 @@ again:
 		}
 		my->mc_wlen[toggle] = 0;
 		toggle ^= 1;
+		pthread_cond_signal(&my->mc_cond);
 	}
+	pthread_cond_signal(&my->mc_cond);
+	pthread_mutex_unlock(&my->mc_mutex);
 	return (THREAD_RET)0;
 #undef DO_WRITE
 }
 
 static int
-mdb_env_cthr_toggle(mdb_copy *my)
+mdb_env_cthr_toggle(mdb_copy *my, int st)
 {
 	int toggle = my->mc_toggle ^ 1;
-
-	pthread_mutex_unlock(&my->mc_mutex[my->mc_toggle]);
-	pthread_mutex_lock(&my->mc_mutex[toggle]);
+	pthread_mutex_lock(&my->mc_mutex);
 	if (my->mc_status) {
-		pthread_mutex_unlock(&my->mc_mutex[toggle]);
+		pthread_mutex_unlock(&my->mc_mutex);
 		return my->mc_status;
 	}
+	while (my->mc_new == 1)
+		pthread_cond_wait(&my->mc_cond, &my->mc_mutex);
+	my->mc_new = st;
 	my->mc_toggle = toggle;
+	pthread_cond_signal(&my->mc_cond);
+	pthread_mutex_unlock(&my->mc_mutex);
 	return 0;
 }
 
@@ -8188,10 +8201,10 @@ mdb_env_cwalk(mdb_copy *my, pgno_t *pg, int flags)
 						if (rc)
 							goto done;
 						if (my->mc_wlen[toggle] >= MDB_WBUF) {
-							rc = mdb_env_cthr_toggle(my);
+							rc = mdb_env_cthr_toggle(my, 1);
 							if (rc)
 								goto done;
-							toggle ^= 1;
+							toggle = my->mc_toggle;
 						}
 						mo = (MDB_page *)(my->mc_wbuf[toggle] + my->mc_wlen[toggle]);
 						memcpy(mo, omp, my->mc_env->me_psize);
@@ -8201,10 +8214,10 @@ mdb_env_cwalk(mdb_copy *my, pgno_t *pg, int flags)
 						if (omp->mp_pages > 1) {
 							my->mc_olen[toggle] = my->mc_env->me_psize * (omp->mp_pages - 1);
 							my->mc_over[toggle] = (char *)omp + my->mc_env->me_psize;
-							rc = mdb_env_cthr_toggle(my);
+							rc = mdb_env_cthr_toggle(my, 1);
 							if (rc)
 								goto done;
-							toggle ^= 1;
+							toggle = my->mc_toggle;
 						}
 						memcpy(NODEDATA(ni), &mo->mp_pgno, sizeof(pgno_t));
 					} else if (ni->mn_flags & F_SUBDATA) {
@@ -8250,10 +8263,10 @@ again:
 			}
 		}
 		if (my->mc_wlen[toggle] >= MDB_WBUF) {
-			rc = mdb_env_cthr_toggle(my);
+			rc = mdb_env_cthr_toggle(my, 1);
 			if (rc)
 				goto done;
-			toggle ^= 1;
+			toggle = my->mc_toggle;
 		}
 		mo = (MDB_page *)(my->mc_wbuf[toggle] + my->mc_wlen[toggle]);
 		mdb_page_copy(mo, mp, my->mc_env->me_psize);
@@ -8286,14 +8299,14 @@ mdb_env_copyfd2(MDB_env *env, HANDLE fd)
 	int rc;
 
 #ifdef _WIN32
-	my.mc_mutex[0] = CreateMutex(NULL, FALSE, NULL);
-	my.mc_mutex[1] = CreateMutex(NULL, FALSE, NULL);
+	my.mc_mutex = CreateMutex(NULL, FALSE, NULL);
+	my.mc_cond = CreateEvent(NULL, FALSE, FALSE, NULL);
 	my.mc_wbuf[0] = _aligned_malloc(MDB_WBUF*2, env->me_psize);
 	if (my.mc_wbuf[0] == NULL)
 		return errno;
 #else
-	pthread_mutex_init(&my.mc_mutex[0], NULL);
-	pthread_mutex_init(&my.mc_mutex[1], NULL);
+	pthread_mutex_init(&my.mc_mutex, NULL);
+	pthread_cond_init(&my.mc_cond, NULL);
 	rc = posix_memalign((void **)&my.mc_wbuf[0], env->me_psize, MDB_WBUF*2);
 	if (rc)
 		return rc;
@@ -8305,11 +8318,10 @@ mdb_env_copyfd2(MDB_env *env, HANDLE fd)
 	my.mc_olen[1] = 0;
 	my.mc_next_pgno = 2;
 	my.mc_status = 0;
+	my.mc_new = 1;
 	my.mc_toggle = 0;
 	my.mc_env = env;
 	my.mc_fd = fd;
-	pthread_mutex_lock(&my.mc_mutex[0]);
-	THREAD_CREATE(thr, mdb_env_copythr, &my);
 
 	/* Do the lock/unlock of the reader mutex before starting the
 	 * write txn.  Otherwise other read txns could block writers.
@@ -8332,6 +8344,7 @@ mdb_env_copyfd2(MDB_env *env, HANDLE fd)
 		}
 	}
 
+	THREAD_CREATE(thr, mdb_env_copythr, &my);
 	mp = (MDB_page *)my.mc_wbuf[0];
 	memset(mp, 0, 2*env->me_psize);
 	mp->mp_pgno = 0;
@@ -8368,21 +8381,28 @@ mdb_env_copyfd2(MDB_env *env, HANDLE fd)
 	}
 	my.mc_wlen[0] = env->me_psize * 2;
 	my.mc_txn = txn;
+	pthread_mutex_lock(&my.mc_mutex);
+	while(my.mc_new)
+		pthread_cond_wait(&my.mc_cond, &my.mc_mutex);
+	pthread_mutex_unlock(&my.mc_mutex);
 	rc = mdb_env_cwalk(&my, &txn->mt_dbs[1].md_root, 0);
 	if (rc == MDB_SUCCESS && my.mc_wlen[my.mc_toggle])
-		rc = mdb_env_cthr_toggle(&my);
-	my.mc_wlen[my.mc_toggle] = 0;
-	pthread_mutex_unlock(&my.mc_mutex[my.mc_toggle]);
+		rc = mdb_env_cthr_toggle(&my, 1);
+	mdb_env_cthr_toggle(&my, -1);
+	pthread_mutex_lock(&my.mc_mutex);
+	while(my.mc_new)
+		pthread_cond_wait(&my.mc_cond, &my.mc_mutex);
+	pthread_mutex_unlock(&my.mc_mutex);
 	THREAD_FINISH(thr);
 leave:
 	mdb_txn_abort(txn);
 #ifdef _WIN32
-	CloseHandle(my.mc_mutex[1]);
-	CloseHandle(my.mc_mutex[0]);
+	CloseHandle(my.mc_cond);
+	CloseHandle(my.mc_mutex);
 	_aligned_free(my.mc_wbuf[0]);
 #else
-	pthread_mutex_destroy(&my.mc_mutex[1]);
-	pthread_mutex_destroy(&my.mc_mutex[0]);
+	pthread_cond_destroy(&my.mc_cond);
+	pthread_mutex_destroy(&my.mc_mutex);
 	free(my.mc_wbuf[0]);
 #endif
 	return rc;