On 2008-07-14 10:10:15 -0700, Christiaan Hofman <[EMAIL PROTECTED]> said:
> > On 14 Jul 2008, at 6:31 PM, Adam Maxwell wrote: > >> On 2008-07-13 08:28:24 -0700, Christiaan Hofman <[EMAIL PROTECTED]> >> said: >> >>> Adam, I hope you still see this. I am a bit uncertain whether >>> BDSKAsynchronousDOServer is stopped properly. Especially if the >>> server >>> thread runloop is stopped, and whether -cleanup is guaranteed to be >>> executed. I could imagine the following errors to occur: >>> >>> 1. send -cleanup >>> 2. set shouldKeepRunning to 0 >>> 3. server thread runloop finishes some long calculation, no new >>> runloop run as shouldKeepRunning == 0 >>> >>> Result: >>> -cleanup is never run, because there is no runloop to pick it up >> >> Sounds plausible. I'm not sure of a way around this, since turning >> "&& >> didRun" into "|| didRun" means that the thread could keep running >> forever unless all the inputs are removed, so it would no longer be a >> guaranteed stop mechanism. >> >>> 1. send -cleanup >>> 2. serverThread executes -cleanup immediately >>> 3. server thread starts new runloop run >>> 4. set shouldKeepRunning to 0 >>> >>> Result: >>> the runloop on the server thread never finishes, as it gets no input >>> anymore >> >> This also seems possible, although invalidating the connection may >> tickle the runloop. Having only thought about this briefly, a safe >> workaround might be to do this in cleanup: >> >> OSAtomicCompareAndSwap32Barrier(1, 0, (int32_t >> *)&serverFlags->shouldKeepRunning); >> [[NSRunLoop currentRunLoop] runMode:NSDefaultRunLoopMode >> beforeDate:[NSDate distantPast]]; >> >> which would ensure the runloop exits. Alternately, running it with a >> short timeout in runDOServerForPorts: instead of +[NSDate >> distantFuture] would work. IIRC I use the finite timeout for a >> similar >> problem in FVConcreteOperationQueue. >> > > That's usually not recommended, because it amounts to polling. > Moreover you would need to wait at least the timeout before it's > finished. Blocking with a timeout isn't the same as polling with a timer. Using a runloop with a timeout is recommended here: http://developer.apple.com/documentation/Cocoa/Conceptual/Multithreading/RunLoopManagement/chapter_6_section_4.html notably on the section "Exiting the Run Loop." >> In fact, setting shouldKeepRunning = 0 in -cleanup would solve the >> first problem, also (I think), providing the message doesn't get >> dropped. There may be some subtle reason it's set in the main thread, >> but there's no comment to that effect. > > That's what I was thinking of, just change the order of the two lines. I was suggesting that the flag be set in the server thread; changing the order wouldn't work...(I see you noticed that below). > The main reason it's set in the main thread is that a running (long) > task may decide to stop executing, e.g. in a long while-loop. If > shouldKeepRunning is set to 0 on the server thread it won't happen > till the current calculation has finished. It won't happen until the end of the calculation loop anyway unless the calculation loop runs the runloop and checks that flag, though, right? > If the order of the two lines is reversed, I think the only problem > can be that cleanup may not be called. So why not do the real cleanup > at the end of -runDOServerForPorts:? I think the only real reason not > to do that was that the runloop needs to be stopped, but it could just > as well be tickled by a further empty (and therefore irrelevant) > method. Then, if that method was not send because the runloop has > already finished, it's not a problem. Yes, deallocating at the end of runDOServerForPorts: ought to work, and is probably cleaner. I'd have it call -cleanup for backwards compatibility, though, since numerous subclasses override it. I wouldn't guarantee that there are no dependencies on the order of -cleanup vs. other teardown, either. -- adam ------------------------------------------------------------------------- Sponsored by: SourceForge.net Community Choice Awards: VOTE NOW! Studies have shown that voting for your favorite open source project, along with a healthy diet, reduces your potential for chronic lameness and boredom. Vote Now at http://www.sourceforge.net/community/cca08 _______________________________________________ Bibdesk-develop mailing list Bibdesk-develop@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/bibdesk-develop
