diff options
Diffstat (limited to 'ChangeLog-98b')
| -rw-r--r-- | ChangeLog-98b | 71 |
1 files changed, 56 insertions, 15 deletions
diff --git a/ChangeLog-98b b/ChangeLog-98b index 800a685ef78..06f6396ca2e 100644 --- a/ChangeLog-98b +++ b/ChangeLog-98b @@ -1,26 +1,67 @@ Fri Oct 16 15:45:08 1998 Douglas C. Schmidt <schmidt@tango.cs.wustl.edu> - * ace/[Hash_]Map_Manager: Removed the use of locking for the - iterators. This is totally broken when using STL-style - iterators, so it's better to let users figure out their usecase, - rather than guess wrong and screwing up their code. + * ace/[Hash_]Map_Manager: Today we decided to remove the use of + locking for the ACE[_Hash]_Map_Manager Iterators. The original + scheme acquired the mutex of the [Hash_]Map_Manager on every + ++operator++/--operator-- call. Not only was this very + inefficient, but it was also essentially useless since it + doesn't protect against arbitrary insertions/deletions in the + underlying map during the iteration. + + Our first thought was to put an ACE_Read_Guard into the iterator + itself and acquire this for the duration of the iteration. + However, this approach is totally broken when using STL-style + iterators since the postfix ++ and -- operators return a copy of + the iterator, which easily causes deadlocks if non-recursive + mutexes are used. + + After much discussion, we decided it's better to let users + figure out their own locking usecase, rather than have the + iterators guess wrong and either screw up their code or yield + substantial inefficiencies. Therefore, the right approach is to + do something like this: + + typedef ACE_Map_Manager <TYPE1, TYPE2, ACE_Thread_Mutex> MAP_MANAGER; + typedef ACE_Map_Iterator <TYPE1, TYPE2, ACE_Thread_Mutex> ITERATOR; + typedef ACE_Map_Entry <TYPE1, TYPE2> ENTRY; + + void + foo (MAP_MANAGER &map) + { + // ... + { + // Explicitly grab the lock and hold it for the duration of + // the iteration. + ACE_READ_GUARD (ACE_Thread_Mutex, ace_mon, map.mutex ()); + + ITERATOR end = map.end (); + + for (ITERATOR iter = map.begin (); + iter != end; + iter++) + { + ENTRY &entry = *iter; + i++; + } + // ... + } Fri Oct 16 14:57:58 1998 Irfan Pyarali <irfan@cs.wustl.edu> - * ace/Hash_Map_Manager and Map_Manager: Fixed the operator++ and - operator--. Also, moved the guard from the individual methods - to the iterator. Now, the read guard is held for the life time - of the iterator. + * ace/Hash_Map_Manager and Map_Manager: Fixed the operator++ and + operator--. Also, moved the guard from the individual methods + to the iterator. Now, the read guard is held for the life time + of the iterator. Fri Oct 16 14:51:57 1998 Nanbor Wang <nanbor@cs.wustl.edu> - * ace/OS.cpp (thr_create): Made sure if users don't specify - whether to spawn threads detached or joinable, we'd change the - creation flag for them so that they are always joinable (not - detached.) This is important for unify the thread behavior on - different platforms that have various default thread creation - policies. Thanks to Susan Liebeskind - <shl@janis.gtri.gatech.edu> for motivating the change. + * ace/OS.cpp (thr_create): Made sure if users don't specify + whether to spawn threads detached or joinable, we'd change the + creation flag for them so that they are always joinable (not + detached.) This is important for unify the thread behavior on + different platforms that have various default thread creation + policies. Thanks to Susan Liebeskind + <shl@janis.gtri.gatech.edu> for motivating the change. Fri Oct 16 01:28:17 1998 Douglas C. Schmidt <schmidt@cs.wustl.edu> |