From b2ae574d39adfe283c61a3ec0c766e8780f345af Mon Sep 17 00:00:00 2001
From: Justus Winter <4winter@informatik.uni-hamburg.de>
Date: Sat, 3 May 2014 03:53:41 +0200
Subject: libports: use a global hash table for the lookups

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/reallocate-port.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

(limited to 'libports/reallocate-port.c')

diff --git a/libports/reallocate-port.c b/libports/reallocate-port.c
index d2adaebb..cc534eb4 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);
-- 
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