[PATCH 1/2] libports: use a global hash table for the lookups

[Justus Winter]

Previously, libports used a hash table per port bucket.  This makes
looking up a port difficult if one does not know the port bucket, as
one has to iterate over all buckets and do a hash table lookup each.

Having to iterate over the buckets makes it necessary to keep a list
of all buckets, which has to be updated and protected by a lock as
well.

Also, the current code in _ports_bucket_class_iterate iterates over
the hash table associated with the bucket given.  When
ports_class_iterate calls this common function, it obtains a reference
to the bucket from one of the ports in the given class.  This will not
work if a class contains ports in different port buckets.  This
limitation is not documented as far as I can see.  Again, having to
maintain this list has its cost and requires serialization.

Use a global hash table for lookups instead.  Keep the per-bucket hash
tables for efficient iteration over buckets.  Furthermore, serialize
access to all hash tables using a separate lock.  Remove the linked
lists of all buckets and all ports in a class.

* libports/bucket-iterate.c (ports_bucket_iterate): Acquire
_ports_htable_lock.  Also, generalize ports_bucket_iterate so that it
takes a pointer to a hash table as first argument.
(ports_bucket_iterate): Ajust call to former function accordingly.
* libports/class-iterate.c (ports_class_iterate): Just call the
generalized _ports_bucket_class_iterate with the global hash table as
argument.
* libports/ports.h (struct port_info): Remove the port class links.
(struct port_bucket): Remove the hash table, and the all buckets link.
(_ports_all_buckets): Remove declaration.
(_ports_htable): New global hash table.
(_ports_htable_lock): Protected by this lock.
* libports/claim-right.c: Adjust accordingly.
* libports/complete-deallocate.c: Likewise.
* libports/create-bucket.c: Likewise.
* libports/create-class.c: Likewise.
* libports/create-internal.c: Likewise.
* libports/destroy-right.c: Likewise.
* libports/import-port.c: Likewise.
* libports/lookup-port.c: Likewise.
* libports/reallocate-from-external.c: Likewise.
* libports/reallocate-port.c: Likewise.
* libports/transfer-right.c: Likewise.
* libports/inhibit-all-rpcs.c: Iterate over the hash table.
* libports/inhibit-bucket-rpcs.c: Likewise, but filter using bucket.
* libports/inhibit-class-rpcs.c: Likewise, but filter using class.
* libports/init.c (_ports_htable): Initialize.
(_ports_htable_lock): Likewise.
---
 libports/bucket-iterate.c           | 16 +++++++++-------
 libports/claim-right.c              |  5 ++++-
 libports/class-iterate.c            | 10 +---------
 libports/complete-deallocate.c      |  7 +++----
 libports/create-bucket.c            |  6 ------
 libports/create-class.c             |  1 -
 libports/create-internal.c          | 19 +++++++++++++------
 libports/destroy-right.c            |  5 +++--
 libports/import-port.c              | 19 +++++++++++++------
 libports/inhibit-all-rpcs.c         | 27 +++++++++++++--------------
 libports/inhibit-bucket-rpcs.c      |  3 ++-
 libports/inhibit-class-rpcs.c       | 27 ++++++++++++++++++---------
 libports/init.c                     |  7 ++++++-
 libports/lookup-port.c              | 23 +++++++++--------------
 libports/ports.h                    | 22 +++++++++++++++++-----
 libports/reallocate-from-external.c | 15 +++++++++++----
 libports/reallocate-port.c          |  9 ++++++++-
 libports/transfer-right.c           | 18 ++++++++++++++----
 18 files changed, 144 insertions(+), 95 deletions(-)

diff --git a/libports/bucket-iterate.c b/libports/bucket-iterate.c
index 2d1b00d..79b6d72 100644
--- a/libports/bucket-iterate.c
+++ b/libports/bucket-iterate.c
@@ -25,7 +25,7 @@
 /* Internal entrypoint for both ports_bucket_iterate and ports_class_iterate.
    If CLASS is non-null, call FUN only for ports in that class.  */
 error_t
-_ports_bucket_class_iterate (struct port_bucket *bucket,
+_ports_bucket_class_iterate (struct hurd_ihash *ht,
                             struct port_class *class,
                             error_t (*fun)(void *))
 {
@@ -36,23 +36,24 @@ _ports_bucket_class_iterate (struct port_bucket *bucket,
   error_t err;
 
   pthread_mutex_lock (&_ports_lock);
+  pthread_rwlock_rdlock (&_ports_htable_lock);
 
-  if (bucket->htable.nr_items == 0)
+  if (ht->nr_items == 0)
     {
-      pthread_mutex_unlock (&_ports_lock);
+      pthread_rwlock_unlock (&_ports_htable_lock);
       return 0;
     }
 
-  nr_items = bucket->htable.nr_items;
+  nr_items = ht->nr_items;
   p = malloc (nr_items * sizeof *p);
   if (p == NULL)
     {
-      pthread_mutex_unlock (&_ports_lock);
+      pthread_rwlock_unlock (&_ports_htable_lock);
       return ENOMEM;
     }
 
   n = 0;
-  HURD_IHASH_ITERATE (&bucket->htable, arg)
+  HURD_IHASH_ITERATE (ht, arg)
     {
       struct port_info *const pi = arg;
 
@@ -63,6 +64,7 @@ _ports_bucket_class_iterate (struct port_bucket *bucket,
          n++;
        }
     }
+  pthread_rwlock_unlock (&_ports_htable_lock);
   pthread_mutex_unlock (&_ports_lock);
 
   if (n != 0 && n != nr_items)
@@ -89,5 +91,5 @@ error_t
 ports_bucket_iterate (struct port_bucket *bucket,
                      error_t (*fun)(void *))
 {
-  return _ports_bucket_class_iterate (bucket, 0, fun);
+  return _ports_bucket_class_iterate (&bucket->htable, NULL, fun);
 }
diff --git a/libports/claim-right.c b/libports/claim-right.c
index 4851ea3..85592ff 100644
--- a/libports/claim-right.c
+++ b/libports/claim-right.c
@@ -34,10 +34,13 @@ ports_claim_right (void *portstruct)
   if (ret == MACH_PORT_NULL)
     return ret;
 
-  pthread_mutex_lock (&_ports_lock);
+  pthread_rwlock_wrlock (&_ports_htable_lock);
+  hurd_ihash_locp_remove (&_ports_htable, pi->ports_htable_entry);
   hurd_ihash_locp_remove (&pi->bucket->htable, pi->hentry);
+  pthread_rwlock_unlock (&_ports_htable_lock);
   err = mach_port_move_member (mach_task_self (), ret, MACH_PORT_NULL);
   assert_perror (err);
+  pthread_mutex_lock (&_ports_lock);
   pi->port_right = MACH_PORT_NULL;
   if (pi->flags & PORT_HAS_SENDRIGHTS)
     {
diff --git a/libports/class-iterate.c b/libports/class-iterate.c
index 1f8878a..df33818 100644
--- a/libports/class-iterate.c
+++ b/libports/class-iterate.c
@@ -23,13 +23,5 @@ error_t
 ports_class_iterate (struct port_class *class,
                     error_t (*fun)(void *))
 {
-  pthread_mutex_lock (&_ports_lock);
-  if (class->ports != 0)
-    {
-      struct port_bucket *bucket = class->ports->bucket;
-      pthread_mutex_unlock (&_ports_lock);
-      return _ports_bucket_class_iterate (bucket, class, fun);
-    }
-  pthread_mutex_unlock (&_ports_lock);
-  return 0;
+  return _ports_bucket_class_iterate (&_ports_htable, class, fun);
 }
diff --git a/libports/complete-deallocate.c b/libports/complete-deallocate.c
index 8ce095b..4768dab 100644
--- a/libports/complete-deallocate.c
+++ b/libports/complete-deallocate.c
@@ -29,16 +29,15 @@ _ports_complete_deallocate (struct port_info *pi)
 
   if (pi->port_right)
     {
+      pthread_rwlock_wrlock (&_ports_htable_lock);
+      hurd_ihash_locp_remove (&_ports_htable, pi->ports_htable_entry);
       hurd_ihash_locp_remove (&pi->bucket->htable, pi->hentry);
+      pthread_rwlock_unlock (&_ports_htable_lock);
       mach_port_mod_refs (mach_task_self (), pi->port_right,
                          MACH_PORT_RIGHT_RECEIVE, -1);
       pi->port_right = MACH_PORT_NULL;
     }
 
-  *pi->prevp = pi->next;
-  if (pi->next)
-    pi->next->prevp = pi->prevp;
-
   pi->bucket->count--;
   pi->class->count--;
 
diff --git a/libports/create-bucket.c b/libports/create-bucket.c
index 52d50c3..2c5f1b6 100644
--- a/libports/create-bucket.c
+++ b/libports/create-bucket.c
@@ -48,11 +48,5 @@ ports_create_bucket ()
 
   hurd_ihash_init (&ret->htable, offsetof (struct port_info, hentry));
   ret->rpcs = ret->flags = ret->count = 0;
-
-  pthread_mutex_lock (&_ports_lock);
-  ret->next = _ports_all_buckets;
-  _ports_all_buckets = ret;
-  pthread_mutex_unlock (&_ports_lock);
-
   return ret;
 }
diff --git a/libports/create-class.c b/libports/create-class.c
index 12c8add..782f52b 100644
--- a/libports/create-class.c
+++ b/libports/create-class.c
@@ -39,7 +39,6 @@ ports_create_class (void (*clean_routine)(void *),
   cl->dropweak_routine = dropweak_routine;
   cl->flags = 0;
   cl->rpcs = 0;
-  cl->ports = NULL;
   cl->count = 0;
   cl->uninhibitable_rpcs = ports_default_uninhibitable_rpcs;
 
diff --git a/libports/create-internal.c b/libports/create-internal.c
index 8551297..8543986 100644
--- a/libports/create-internal.c
+++ b/libports/create-internal.c
@@ -81,15 +81,22 @@ _ports_create_port_internal (struct port_class *class,
       goto loop;
     }
 
+  pthread_rwlock_wrlock (&_ports_htable_lock);
+  err = hurd_ihash_add (&_ports_htable, port, pi);
+  if (err)
+    {
+      pthread_rwlock_unlock (&_ports_htable_lock);
+      goto lose;
+    }
   err = hurd_ihash_add (&bucket->htable, port, pi);
   if (err)
-    goto lose;
+    {
+      hurd_ihash_locp_remove (&_ports_htable, pi->ports_htable_entry);
+      pthread_rwlock_unlock (&_ports_htable_lock);
+      goto lose;
+    }
+  pthread_rwlock_unlock (&_ports_htable_lock);
 
-  pi->next = class->ports;
-  pi->prevp = &class->ports;
-  if (class->ports)
-    class->ports->prevp = &pi->next;
-  class->ports = pi;
   bucket->count++;
   class->count++;
   pthread_mutex_unlock (&_ports_lock);
diff --git a/libports/destroy-right.c b/libports/destroy-right.c
index 65e19c7..448b379 100644
--- a/libports/destroy-right.c
+++ b/libports/destroy-right.c
@@ -30,12 +30,13 @@ ports_destroy_right (void *portstruct)
 
   if (pi->port_right != MACH_PORT_NULL)
     {
-      pthread_mutex_lock (&_ports_lock);
+      pthread_rwlock_wrlock (&_ports_htable_lock);
+      hurd_ihash_locp_remove (&_ports_htable, pi->ports_htable_entry);
       hurd_ihash_locp_remove (&pi->bucket->htable, pi->hentry);
+      pthread_rwlock_unlock (&_ports_htable_lock);
       err = mach_port_mod_refs (mach_task_self (), pi->port_right,
                                MACH_PORT_RIGHT_RECEIVE, -1);
       assert_perror (err);
-      pthread_mutex_unlock (&_ports_lock);
 
       pi->port_right = MACH_PORT_NULL;
 
diff --git a/libports/import-port.c b/libports/import-port.c
index 226f47e..2660672 100644
--- a/libports/import-port.c
+++ b/libports/import-port.c
@@ -75,15 +75,22 @@ ports_import_port (struct port_class *class, struct 
port_bucket *bucket,
       goto loop;
     }
 
+  pthread_rwlock_wrlock (&_ports_htable_lock);
+  err = hurd_ihash_add (&_ports_htable, port, pi);
+  if (err)
+    {
+      pthread_rwlock_unlock (&_ports_htable_lock);
+      goto lose;
+    }
   err = hurd_ihash_add (&bucket->htable, port, pi);
   if (err)
-    goto lose;
+    {
+      hurd_ihash_locp_remove (&_ports_htable, pi->ports_htable_entry);
+      pthread_rwlock_unlock (&_ports_htable_lock);
+      goto lose;
+    }
+  pthread_rwlock_unlock (&_ports_htable_lock);
 
-  pi->next = class->ports;
-  pi->prevp = &class->ports;
-  if (class->ports)
-    class->ports->prevp = &pi->next;
-  class->ports = pi;
   bucket->count++;
   class->count++;
   pthread_mutex_unlock (&_ports_lock);
diff --git a/libports/inhibit-all-rpcs.c b/libports/inhibit-all-rpcs.c
index d4a54ba..27e2ec5 100644
--- a/libports/inhibit-all-rpcs.c
+++ b/libports/inhibit-all-rpcs.c
@@ -36,24 +36,23 @@ ports_inhibit_all_rpcs ()
       struct port_bucket *bucket;
       int this_one = 0;
 
-      for (bucket = _ports_all_buckets; bucket; bucket = bucket->next)
+      pthread_rwlock_rdlock (&_ports_htable_lock);
+      HURD_IHASH_ITERATE (&_ports_htable, portstruct)
        {
-         HURD_IHASH_ITERATE (&bucket->htable, portstruct)
+         struct rpc_info *rpc;
+         struct port_info *pi = portstruct;
+
+         for (rpc = pi->current_rpcs; rpc; rpc = rpc->next)
            {
-             struct rpc_info *rpc;
-             struct port_info *pi = portstruct;
-         
-             for (rpc = pi->current_rpcs; rpc; rpc = rpc->next)
-               {
-                 /* Avoid cancelling the calling thread if it's currently
-                    handling a RPC.  */
-                 if (rpc->thread == hurd_thread_self ())
-                   this_one = 1;
-                 else
-                   hurd_thread_cancel (rpc->thread);
-               }
+             /* Avoid cancelling the calling thread if it's currently
+                handling a RPC.  */
+             if (rpc->thread == hurd_thread_self ())
+               this_one = 1;
+             else
+               hurd_thread_cancel (rpc->thread);
            }
        }
+      pthread_rwlock_unlock (&_ports_htable_lock);
 
       while (_ports_total_rpcs > this_one)
        {
diff --git a/libports/inhibit-bucket-rpcs.c b/libports/inhibit-bucket-rpcs.c
index 965aa03..82efdf5 100644
--- a/libports/inhibit-bucket-rpcs.c
+++ b/libports/inhibit-bucket-rpcs.c
@@ -35,6 +35,7 @@ ports_inhibit_bucket_rpcs (struct port_bucket *bucket)
     {
       int this_one = 0;
 
+      pthread_rwlock_rdlock (&_ports_htable_lock);
       HURD_IHASH_ITERATE (&bucket->htable, portstruct)
        {
          struct rpc_info *rpc;
@@ -49,7 +50,7 @@ ports_inhibit_bucket_rpcs (struct port_bucket *bucket)
                hurd_thread_cancel (rpc->thread);
            }
        }
-
+      pthread_rwlock_unlock (&_ports_htable_lock);
 
       while (bucket->rpcs > this_one)
        {
diff --git a/libports/inhibit-class-rpcs.c b/libports/inhibit-class-rpcs.c
index 7ee8653..9a87a5f 100644
--- a/libports/inhibit-class-rpcs.c
+++ b/libports/inhibit-class-rpcs.c
@@ -36,15 +36,24 @@ ports_inhibit_class_rpcs (struct port_class *class)
       struct rpc_info *rpc;
       int this_one = 0;
 
-      for (pi = class->ports; pi; pi = pi->next)
-       for (rpc = pi->current_rpcs; rpc; rpc = rpc->next)
-         {
-           /* Avoid cancelling the calling thread.  */
-           if (rpc->thread == hurd_thread_self ())
-             this_one = 1;
-           else
-             hurd_thread_cancel (rpc->thread);
-         }
+      pthread_rwlock_rdlock (&_ports_htable_lock);
+      HURD_IHASH_ITERATE (&_ports_htable, portstruct)
+       {
+         struct rpc_info *rpc;
+         struct port_info *pi = portstruct;
+         if (pi->class != class)
+           continue;
+
+         for (rpc = pi->current_rpcs; rpc; rpc = rpc->next)
+           {
+             /* Avoid cancelling the calling thread.  */
+             if (rpc->thread == hurd_thread_self ())
+               this_one = 1;
+             else
+               hurd_thread_cancel (rpc->thread);
+           }
+       }
+      pthread_rwlock_unlock (&_ports_htable_lock);
 
       while (class->rpcs > this_one)
        {
diff --git a/libports/init.c b/libports/init.c
index 3ef5388..4a68cb8 100644
--- a/libports/init.c
+++ b/libports/init.c
@@ -19,9 +19,14 @@
    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. */
 
 #include "ports.h"
+#include <stddef.h>
 
 pthread_mutex_t _ports_lock = PTHREAD_MUTEX_INITIALIZER;
 pthread_cond_t _ports_block = PTHREAD_COND_INITIALIZER;
-struct port_bucket *_ports_all_buckets;
+
+struct hurd_ihash _ports_htable =
+  HURD_IHASH_INITIALIZER (offsetof (struct port_info, ports_htable_entry));
+pthread_rwlock_t _ports_htable_lock = PTHREAD_RWLOCK_INITIALIZER;
+
 int _ports_total_rpcs;
 int _ports_flags;
diff --git a/libports/lookup-port.c b/libports/lookup-port.c
index f79f6f0..858ee11 100644
--- a/libports/lookup-port.c
+++ b/libports/lookup-port.c
@@ -26,27 +26,22 @@ ports_lookup_port (struct port_bucket *bucket,
                   mach_port_t port,
                   struct port_class *class)
 {
-  struct port_info *pi = 0;
-  
+  struct port_info *pi;
+
   pthread_mutex_lock (&_ports_lock);
+  pthread_rwlock_rdlock (&_ports_htable_lock);
 
-  if (bucket)
-    pi = hurd_ihash_find (&bucket->htable, port);
-  else
-    for (bucket = _ports_all_buckets; bucket; bucket = bucket->next)
-      {
-       pi = hurd_ihash_find (&bucket->htable, port);
-       if (pi)
-         break;
-      }
-  
-  if (pi && class && pi->class != class)
+  pi = hurd_ihash_find (&_ports_htable, port);
+  if (pi
+      && ((class && pi->class != class)
+          || (bucket && pi->bucket != bucket)))
     pi = 0;
 
   if (pi)
     pi->refcnt++;
 
+  pthread_rwlock_unlock (&_ports_htable_lock);
   pthread_mutex_unlock (&_ports_lock);
-  
+
   return pi;
 }
diff --git a/libports/ports.h b/libports/ports.h
index 7f13124..6922162 100644
--- a/libports/ports.h
+++ b/libports/ports.h
@@ -48,7 +48,7 @@ struct port_info
   struct rpc_info *current_rpcs;
   struct port_bucket *bucket;
   hurd_ihash_locp_t hentry;
-  struct port_info *next, **prevp; /* links on port_class list */
+  hurd_ihash_locp_t ports_htable_entry;
 };
 typedef struct port_info *port_info_t;
 
@@ -61,11 +61,12 @@ typedef struct port_info *port_info_t;
 struct port_bucket
 {
   mach_port_t portset;
+  /* Per-bucket hash table used for fast iteration.  Access must be
+     serialized using _ports_htable_lock.  */
   struct hurd_ihash htable;
   int rpcs;
   int flags;
   int count;
-  struct port_bucket *next;
 };
 /* FLAGS above are the following: */
 #define PORT_BUCKET_INHIBITED  PORTS_INHIBITED
@@ -78,7 +79,6 @@ struct port_class
 {
   int flags;
   int rpcs;
-  struct port_info *ports;
   int count;
   void (*clean_routine) (void *);
   void (*dropweak_routine) (void *);
@@ -277,7 +277,7 @@ error_t ports_class_iterate (struct port_class *class,
                             error_t (*fun)(void *port));
 
 /* Internal entrypoint for above two.  */
-error_t _ports_bucket_class_iterate (struct port_bucket *bucket,
+error_t _ports_bucket_class_iterate (struct hurd_ihash *ht,
                                     struct port_class *class,
                                     error_t (*fun)(void *port));
 
@@ -402,7 +402,19 @@ extern kern_return_t
 /* Private data */
 extern pthread_mutex_t _ports_lock;
 extern pthread_cond_t _ports_block;
-extern struct port_bucket *_ports_all_buckets;
+
+/* A global hash table mapping port names to port_info objects.  This
+   table is used for port lookups and to iterate over classes.
+
+   A port in this hash table carries an implicit light reference.
+   When the reference counts reach zero, we call
+   _ports_complete_deallocate.  There we reacquire our lock
+   momentarily to check whether someone else reacquired a reference
+   through the hash table.  */
+extern struct hurd_ihash _ports_htable;
+/* Access to the hash table is protected by this lock.  */
+extern pthread_rwlock_t _ports_htable_lock;
+
 extern int _ports_total_rpcs;
 extern int _ports_flags;
 #define _PORTS_INHIBITED       PORTS_INHIBITED
diff --git a/libports/reallocate-from-external.c 
b/libports/reallocate-from-external.c
index 8cccb2a..9944b39 100644
--- a/libports/reallocate-from-external.c
+++ b/libports/reallocate-from-external.c
@@ -43,8 +43,11 @@ ports_reallocate_from_external (void *portstruct, 
mach_port_t receive)
                            MACH_PORT_RIGHT_RECEIVE, -1);
   assert_perror (err);
 
+  pthread_rwlock_wrlock (&_ports_htable_lock);
+  hurd_ihash_locp_remove (&_ports_htable, pi->ports_htable_entry);
   hurd_ihash_locp_remove (&pi->bucket->htable, pi->hentry);
-  
+  pthread_rwlock_unlock (&_ports_htable_lock);
+
   if ((pi->flags & PORT_HAS_SENDRIGHTS) && !stat.mps_srights)
     {
       dropref = 1;
@@ -59,11 +62,15 @@ ports_reallocate_from_external (void *portstruct, 
mach_port_t receive)
   pi->port_right = receive;
   pi->cancel_threshold = 0;
   pi->mscount = stat.mps_mscount;
-  
-  err = hurd_ihash_add (&pi->bucket->htable, receive, pi);
+
+  pthread_rwlock_wrlock (&_ports_htable_lock);
+  err = hurd_ihash_add (&_ports_htable, receive, pi);
   assert_perror (err);
+  err = hurd_ihash_add (&pi->bucket->htable, receive, pi);
+  pthread_rwlock_unlock (&_ports_htable_lock);
   pthread_mutex_unlock (&_ports_lock);
-  
+  assert_perror (err);
+
   mach_port_move_member (mach_task_self (), receive, pi->bucket->portset);
   
   if (stat.mps_srights)
diff --git a/libports/reallocate-port.c b/libports/reallocate-port.c
index d2adaeb..cc534eb 100644
--- a/libports/reallocate-port.c
+++ b/libports/reallocate-port.c
@@ -36,7 +36,10 @@ ports_reallocate_port (void *portstruct)
                            MACH_PORT_RIGHT_RECEIVE, -1);
   assert_perror (err);
 
+  pthread_rwlock_wrlock (&_ports_htable_lock);
+  hurd_ihash_locp_remove (&_ports_htable, pi->ports_htable_entry);
   hurd_ihash_locp_remove (&pi->bucket->htable, pi->hentry);
+  pthread_rwlock_unlock (&_ports_htable_lock);
 
   err = mach_port_allocate (mach_task_self (), MACH_PORT_RIGHT_RECEIVE,
                            &pi->port_right);
@@ -48,9 +51,13 @@ ports_reallocate_port (void *portstruct)
     }
   pi->cancel_threshold = 0;
   pi->mscount = 0;
-  err = hurd_ihash_add (&pi->bucket->htable, pi->port_right, pi);
+  pthread_rwlock_wrlock (&_ports_htable_lock);
+  err = hurd_ihash_add (&_ports_htable, pi->port_right, pi);
   assert_perror (err);
+  err = hurd_ihash_add (&pi->bucket->htable, pi->port_right, pi);
+  pthread_rwlock_unlock (&_ports_htable_lock);
   pthread_mutex_unlock (&_ports_lock);
+  assert_perror (err);
 
   err = mach_port_move_member (mach_task_self (), pi->port_right, 
                               pi->bucket->portset);
diff --git a/libports/transfer-right.c b/libports/transfer-right.c
index 72488a9..3f48290 100644
--- a/libports/transfer-right.c
+++ b/libports/transfer-right.c
@@ -41,7 +41,10 @@ ports_transfer_right (void *tostruct,
   port = frompi->port_right;
   if (port != MACH_PORT_NULL)
     {
+      pthread_rwlock_wrlock (&_ports_htable_lock);
+      hurd_ihash_locp_remove (&_ports_htable, frompi->ports_htable_entry);
       hurd_ihash_locp_remove (&frompi->bucket->htable, frompi->hentry);
+      pthread_rwlock_unlock (&_ports_htable_lock);
       frompi->port_right = MACH_PORT_NULL;
       if (frompi->flags & PORT_HAS_SENDRIGHTS)
        {
@@ -54,7 +57,10 @@ ports_transfer_right (void *tostruct,
   /* Destroy the existing right in TOPI. */
   if (topi->port_right != MACH_PORT_NULL)
     {
+      pthread_rwlock_wrlock (&_ports_htable_lock);
+      hurd_ihash_locp_remove (&_ports_htable, topi->ports_htable_entry);
       hurd_ihash_locp_remove (&topi->bucket->htable, topi->hentry);
+      pthread_rwlock_unlock (&_ports_htable_lock);
       err = mach_port_mod_refs (mach_task_self (), topi->port_right,
                                MACH_PORT_RIGHT_RECEIVE, -1);
       assert_perror (err);
@@ -74,10 +80,16 @@ ports_transfer_right (void *tostruct,
   topi->port_right = port;
   topi->cancel_threshold = frompi->cancel_threshold;
   topi->mscount = frompi->mscount;
-  
+
+  pthread_mutex_unlock (&_ports_lock);
+
   if (port)
     {
+      pthread_rwlock_wrlock (&_ports_htable_lock);
+      err = hurd_ihash_add (&_ports_htable, port, topi);
+      assert_perror (err);
       err = hurd_ihash_add (&topi->bucket->htable, port, topi);
+      pthread_rwlock_unlock (&_ports_htable_lock);
       assert_perror (err);
       if (topi->bucket != frompi->bucket)
         {
@@ -86,9 +98,7 @@ ports_transfer_right (void *tostruct,
          assert_perror (err);
        }
     }
-  
-  pthread_mutex_unlock (&_ports_lock);
-  
+
   /* Take care of any lowered reference counts. */
   if (dereffrompi)
     ports_port_deref (frompi);
-- 
2.1.0