BorlandTalk.com Borland discussion newsgroups   Archives   FAQ   Search   Memberlist   Usergroups   Register   Profile   Log in to check your private messages   Log in  Deadlock when both IBX and BDE objects used in different thr          BorlandTalk.com Forum Index -> C++ Builder Databases (InterBase Express) View previous topic :: View next topic   Author Message Max Guest Posted: Wed Oct 19, 2005 11:08 pm    Post subject: Deadlock when both IBX and BDE objects used in different thr I have the big LEGACY application in BCB6, which uses many BDE components (TDatabase, TQuery, etc). One of the modules has to modify several tables in the interbase database, when data in another table were modified. Application has a thread A (TThread), which encapsulates the required database modification code (using BDE objects, see above). The main thread has IBEvents and TIBDatabase objects. TIBDatabase object connects to database in the constructor of the main form, and IBEvents fires its OnEventAlert event when the After Update trigger in the database table POST_EVENT. This OnEventAlert event sets the Windows event, which is waited for (WaitForMultipleObjects) in the thread A. Upon return from WaitForMultipleObjects, thread A resets this Windows event, and performs the needed operations on the database (all BDE objects were declared and defined in the TThread::Execute method, also new session was open there), and waits again. This thread waits for several different Windows events, and it acts differently depending on the event received (this is the reason to have this thread). This awkward construct (use of both BDE and IBX) is because this application has been written long ago when IBEvents was located in BDE group and used TDatabase. Replacing BDE elements for IBX is difficult, because application is big, and it uses InfoPower Controls, which require BDE data access components. However, this construct does not work. Either thread A hangs while connecting to the database (if thread A connects the TDatabase after connecting the TIBDatabase in the main thread) or OnEventAlert event is never fired (if TDatabase and IBDatabase connect to the database in the opposite order). It looks IBX and BDE objects interfere when used in different threads. I moved all database operations, which have been located previously in the thread A, into the Synchronize function of the thread A (now all TDatabase, TQuery, ets. are declared and defined in the main thread, and two connections to database are still used). Everything works great. However, this is very awkward, and I do not understand why BDE objects work in different threads (when separate sessions are used), but BDE and IBX do not. The question is how could I get rid of the Syncronize method, and move BDE objects into thread A? Does the BDE version of IBEvents exist? Thanks for reply... Max Fish Back to top Wayne Niddery [TeamB] Guest Posted: Thu Oct 20, 2005 3:34 am    Post subject: Re: Deadlock when both IBX and BDE objects used in different Max wrote: Quote: I have the big LEGACY application in BCB6, which uses many BDE components (TDatabase, TQuery, etc). [snip] Replacing BDE elements for IBX is difficult, because application is big, and it uses InfoPower Controls, which require BDE data access components. The Infopower controls for this late a version of BCB should not require BDE, they should work with any TDataset descendant. Quote: However, this construct does not work. Either thread A hangs while connecting to the database (if thread A connects the TDatabase after connecting the TIBDatabase in the main thread) or OnEventAlert event is never fired (if TDatabase and IBDatabase connect to the database in the opposite order). It looks IBX and BDE objects interfere when used in different threads. There should be no interaction at all between the BDE and IBX components. You have done right as far as making sure the thread has its own BDE objects, however I think you'll find the problem is that the BDE simply cannot handle working in threads very well - I've seen and experienced problems with this myself in the past. While it may be some work to do, the very best thing you can do is switch the thread to use IBX components and get rid of the BDE components there. It will be worth the effort. -- Wayne Niddery - Logic Fundamentals, Inc. (www.logicfundamentals.com) RADBooks: http://www.logicfundamentals.com/RADBooks.html "Some see private enterprise as a predatory target to be shot, others as a cow to be milked, but few are those who see it as a sturdy horse pulling the wagon." - Winston Churchill Back to top Steve Guest Posted: Thu Oct 20, 2005 10:00 pm    Post subject: Re: Deadlock when both IBX and BDE objects used in different Max wrote: Quote: table POST_EVENT. This OnEventAlert event sets the Windows event, which is waited for (WaitForMultipleObjects) in the thread A. Upon return from WaitForMultipleObjects, thread A resets this Windows event, and performs the needed operations on the You might try MsgWaitForMultipleObjectsEx instead of WaitForMultipleObjects. This allows the message queue to continue to process. In my TThreaded application switching resolved a couple of my deadlocks. I assume that both the BDE and IBX access Forms and such, thus need the message processing to continue. Back to top Jeff Overcash (TeamB) Guest Posted: Thu Oct 20, 2005 10:03 pm    Post subject: Re: Deadlock when both IBX and BDE objects used in different "Wayne Niddery [TeamB]" wrote: Quote: There should be no interaction at all between the BDE and IBX components. You have done right as far as making sure the thread has its own BDE objects, however I think you'll find the problem is that the BDE simply cannot handle working in threads very well - I've seen and experienced problems with this myself in the past. While it may be some work to do, the very best thing you can do is switch the thread to use IBX components and get rid of the BDE components there. It will be worth the effort. Also don't forget that events don't actually fire until you commit the transaction that you raise them in. -- Jeff Overcash (TeamB) (Please do not email me directly unless asked. Thank You) Your friends will know you better in the first minute you meet than your acquaintances will know you in a thousand years. 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