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diff --git a/ACE/docs/ACE-FMM.html b/ACE/docs/ACE-FMM.html new file mode 100644 index 00000000000..0b591d263c8 --- /dev/null +++ b/ACE/docs/ACE-FMM.html @@ -0,0 +1,332 @@ +<!-- $Id$ --> + +<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML//EN"> +<html> + <head> + <title>ACE FMM</title> + </head> + + <body bgcolor=#ffffff> +<center> +<font face=helvetica size=5>ACE Frequently Made Mistakes</font> + +<br> +<br> +<table border=0 cellpadding=3 cellspacing=1 width=550> + +<tr> +<td align=right valign=top> + <b>symptom</b> +</td> +<td align=left valign=top> + ACE_Task::getq() returns the error + <b>resource temporarily unavailable</b> +</td> +</tr> +<tr> +<td align=right valign=top> + <b>probable cause</b> +</td> +<td align=left valign=top> + Your Task is a subclass of ACE_Task<ACE_NULL_SYNCH> and + you are using it in a multithreaded program. +</td> +</tr> +<tr> +<td align=right valign=top> + <b>solution</b> +</td> +<td align=left valign=top> + Try using ACE_Task<ACE_MT_SYNCH> + instead so that the associated Message_Queue + is configured for access by multiple threads. +</td> +<tr><td colspan=2><hr noshade></td></tr> + +<tr> +<td align=right valign=top> + <b>symptom</b> +</td> +<td align=left valign=top> + ACE_Task::wait() throws an assert violation +</td> +</tr> +<tr> +<td align=right valign=top> + <b>probable cause</b> +</td> +<td align=left valign=top> + When you activate()d your Task, you specified + THR_DETACHED, which causes wait() to be unable to perform what you + want it to. +</td> +</tr> +<tr> +<td align=right valign=top> + <b>solution</b> +</td> +<td align=left valign=top> + Make sure you specify the flag THR_JOINABLE when activating + your ACE_Task object. +</td> +<tr><td colspan=2><hr noshade></td></tr> + + + +<tr> +<td align=right valign=top> + <b>symptom</b> +</td> +<td align=left valign=top> + Apparent race conditions when spawning threads (or activating Tasks) + from within a constructor. +</td> +</tr> +<tr> +<td align=right valign=top> + <b>probable cause</b> +</td> +<td align=left valign=top> + You are not guaranteed to have a valid <b>this</b> pointer + until the constructor has exited. Threads spawned from + a constructor are free to run + immediately, and may attempt to use an invalid <b>this</b> pointer. + +</td> +</tr> +<tr> +<td align=right valign=top> + <b>solution</b> +</td> +<td align=left valign=top> + Move your Task activations and other thread-spawning activites + <b>out</b> of the constructor. +</td> +<tr><td colspan=2><hr noshade></td></tr> + + + +<tr> +<td align=right valign=top> + <b>symptom</b> +</td> +<td align=left valign=top> + Compiler issues warnings/erros regarding using too few template + arguments, such as "'ACE_Svc_Handler' : too few template arguments". +</td> +</tr> +<tr> +<td align=right valign=top> + <b>probable cause</b> +</td> +<td align=left valign=top> + Instead of using the appropriate macro, you supplied an actual class + name as a parameter. This will fail depending upon platform and compiler, + due to the way templates are handled. +</td> +</tr> +<tr> +<td align=right valign=top> + <b>solution</b> +</td> +<td align=left valign=top> + Instead of instantiating a template class like <b>ACE_Svc_Handler<<u>ACE_SOCK_Stream</u>, ACE_NULL_SYNCH></b>, use the form of <b>ACE_Svc_Handler<<u>ACE_SOCK_STREAM</u>, ACE_NULL_SYNCH></b> which circumvents the platform peculiarities by using the macro. This also applies to some other template classes. +</td> +<tr><td colspan=2><hr noshade></td></tr> + + + +<tr> +<td align=right valign=top> + <b>symptom</b> +</td> +<td align=left valign=top> + Unable to compare ACE_thread_t variables (such as ACE_Thread::self()) + using operator== (). +</td> +</tr> +<tr> +<td align=right valign=top> + <b>probable cause</b> +</td> +<td align=left valign=top> + On some platforms, thread ids are numeric, and on some, they aren't. On some + implementations, simple a == b comparisons + are legal and sane. Some are not. + +</td> +</tr> +<tr> +<td align=right valign=top> + <b>solution</b> +</td> +<td align=left valign=top> + Use the <b>ACE_OS::thr_equal()</b> function to reliably compare thread + ids, regardless of platform. +</td> +<tr><td colspan=2><hr noshade></td></tr> + +<tr> +<td align=right valign=top> + <b>symptom</b> +</td> +<td align=left valign=top> + ACE_Reactor::run_event_loop() does not seem to function correctly + for a Reactor created in your application. +</td> +</tr> +<tr> +<td align=right valign=top> + <b>probable cause</b> +</td> +<td align=left valign=top> + You have not set the ACE_Reactor::instance() to refer to your new reactor. + run_event_loop only functions on the reactor currently installed as the + global Singleton. +</td> +</tr> +<tr> +<td align=right valign=top> + <b>solution</b> +</td> +<td align=left valign=top> + Use the <b>ACE_Reactor::instance(ACE_Reactor *, + int delete_reactor = 0)</b> static method to install your reactor as the global + Singleton before calling run_event_loop(). +</td> +<tr><td colspan=2><hr noshade></td></tr> + + + + + +<tr> +<td align=right valign=top> + <b>symptom</b> +</td> +<td align=left valign=top> +Infinite recursion when you invoke ACE_Reactor::remove_handler() +</td> +</tr> +<tr> +<td align=right valign=top> + <b>probable cause</b> +</td> +<td align=left valign=top> +You are invoking remove_handler() from within handle_close() (or a +method invoked by handle_close()) but you have not specified the +DONT_CALL flag. +</td> +</tr> +<tr> +<td align=right valign=top> + <b>solution</b> +</td> +<td align=left valign=top> +Be sure to <b>OR</b> in the DONT_CALL flag in this situation.<br> +e.g. --<br> +<ul><pre> +int MyHandler::handle_close (ACE_HANDLE handle, + ACE_Reactor_Mask close_mask) +{ + ... + my_reactor_->remove_handler( this, + ACE_Event_Handler::READ_MASK | + ACE_Event_Handler::DONT_CALL ); + ... + return 0; +} +</pre></ul> + +</td> +<tr><td colspan=2><hr noshade></td></tr> + +<tr> +<td align=right valign=top> + <b>symptom</b> +</td> +<td align=left valign=top> + Application crashes after deleting Event_Handler. +</td> +</tr> +<tr> +<td align=right valign=top> + <b>probable cause</b> +</td> +<td align=left valign=top> + You left a dangling pointer to the Event_Handler in the Reactor. + It is the application's responsibility to remove all pending notifications, + timer events and completely remove the event handler I/O registrations + before removing the event handler. + + Also, the application should remove the event handler from the reactor + <b>before</b> closing the underlying file descriptor / handle. + Otherwise: + <ul> + <li>The reactor does not know how to remove the event handler, because the + handle is used as the identifier for the event handlers</li> + <li>The file descriptor / handle may be reused by another thread, leading to + nasty race conditions.</li> + </ul> +</td> +</tr> +<tr> +<td align=right valign=top> + <b>solution</b> +</td> +<td align=left valign=top> + <ul> + <li>Use reference counted event handlers. The reactor and the application + cooperate to remove the event handler when the last reference goes away. + </li> + <li>Remember to call <tt>purge_pending_notifications()</tt>, + <tt>remove_handler()</tt> and <tt>cancel_timer()</tt> before deleting the + event handler. + </li> + </ul> +</td> +<td align=left valign=top> + +</td> +<tr><td colspan=2><hr noshade></td></tr> + +<!-- + +<tr> +<td align=right valign=top> + <b>symptom</b> +</td> +<td align=left valign=top> + +</td> +</tr> +<tr> +<td align=right valign=top> + <b>probable cause</b> +</td> +<td align=left valign=top> + +</td> +</tr> +<tr> +<td align=right valign=top> + <b>solution</b> +</td> +<td align=left valign=top> + +</td> +<tr><td colspan=2><hr noshade></td></tr> + +--> +<tr> +<td align=center colspan=2> +<font size=2>maintained by <a href="mailto:bob@werken.com">bob@werken.com</a></font> +</td> +</tr> + +</table> +</center> +Back to <A HREF="index.html">ACE Documentation Home</A>. +</body> +</html> + |