Re: [plt-dev] Error message from test-engine
I think Eli recently changed the way force & delay work. Perhaps that has something to do with this? Robby On Mon, Nov 16, 2009 at 6:57 PM, Carl Eastlund wrote: > I got the following error while trying to modify the way Dracula uses > check-expect tests: > > force: reentrant promise gc-on-bitmap > > === context === > /Users/cce/plt/2009-11-16/collects/scheme/promise.ss:94:10 > /Users/cce/plt/2009-11-16/collects/scheme/private/more-scheme.ss:274:2: > call-with-exception-handler > /Users/cce/plt/2009-11-16/collects/scheme/promise.ss:86:0: force/generic > /Users/cce/plt/2009-11-16/collects/framework/private/frame.ss:650:4: > register-gc-blit method in ...ork/private/frame.ss:493:2 > /Users/cce/plt/2009-11-16/collects/framework/private/frame.ss:493:2 > /Users/cce/plt/2009-11-16/collects/scheme/private/class-internal.ss:2699:0: > continue-make-object > /Users/cce/plt/2009-11-16/collects/framework/private/frame.ss:749:2 > /Users/cce/plt/2009-11-16/collects/scheme/private/class-internal.ss:2699:0: > continue-make-object > /Users/cce/plt/2009-11-16/collects/scheme/private/class-internal.ss:2699:0: > continue-make-object > /Users/cce/plt/2009-11-16/collects/framework/private/standard-menus.ss:179:2 > /Users/cce/plt/2009-11-16/collects/scheme/private/class-internal.ss:2699:0: > continue-make-object > /Users/cce/plt/2009-11-16/collects/test-engine/test-display.scm:335:2 > /Users/cce/plt/2009-11-16/collects/scheme/private/class-internal.ss:2699:0: > continue-make-object > /Users/cce/plt/2009-11-16/collects/scheme/private/class-internal.ss:2621:2: > make-object > /Users/cce/plt/2009-11-16/collects/test-engine/test-display.scm:70:4: > display-results method in test-display% > > I don't think anything I did should cause this, but I'm not sure quite > what happened so I can't say for sure. I do know my program had two > check-expect tests, and when this error showed up the check-expect > output displayed three results (my first test once and my second test > twice). > > Does anyone know what might be causing this? > > Carl Eastlund > _ > For list-related administrative tasks: > http://list.cs.brown.edu/mailman/listinfo/plt-dev > _ For list-related administrative tasks: http://list.cs.brown.edu/mailman/listinfo/plt-dev
Re: [plt-dev] Error message from test-engine
On Nov 16, Carl Eastlund wrote: > I got the following error while trying to modify the way Dracula uses > check-expect tests: > > force: reentrant promise gc-on-bitmap > [...] > > I don't think anything I did should cause this, but I'm not sure > quite what happened so I can't say for sure. I do know my program > had two check-expect tests, and when this error showed up the > check-expect output displayed three results (my first test once and > my second test twice). > > Does anyone know what might be causing this? This error happens when a promise is forced while it is forced. For example: -> (define p (delay (force p))) -> (force p) force: reentrant promise p This is especially tricky when multiple threads are involved: -> (define p (delay (sleep 5))) -> (thread (lambda () (force p))) # -> (force p) force: reentrant promise p which could be a problem since threads are involved. As for what Robby said -- I comitted some major extension to `scheme/promise', but the plain `delay'/`force'/`lazy' should be doing exactly the same thing they did before, so no *new* problems should be introduced. So, what I think you should do now is: 1. Try to undo my changes to `scheme/promise' and see if you get the same error. You can just use the contents of the file from 4.2.2 for this. If it doesn't fail, then there might be a bug in the extension, and I'll need some minimal-ish code that reproduces it. 2. But I think that it's likely it will fail too. In that case, you're probably running against the thread problem that I've demonstrated above. (If you look at your stack trace, you'll see that there is one `force/generic', which is what you'd get from my thread example, but the first one will have two.) The good news is that one of the new extensions that I added is `delay/sync' -- this is a kind of a promise that can be forced from multiple threads, the first one will compute it and the rest will block until it's ready. So, if it does fail, you should look around for code that uses `delay'/`force', and see if you can fix it by using `delay/sync'. BTW, this restriction that makes plain promises less useful with multiple threads is relatively new (since v4). The older version wouldn't throw that error -- but it would have the obvious race conditions, which means that the promise will be forced multiple time, and one will get to stay. -- ((lambda (x) (x x)) (lambda (x) (x x))) Eli Barzilay: http://barzilay.org/ Maze is Life! _ For list-related administrative tasks: http://list.cs.brown.edu/mailman/listinfo/plt-dev
Re: [plt-dev] Error message from test-engine
The promise in question has been there for a very long time (10+ years, I'd guess), but there definitely could be treading problems. Perhaps just changing (in framework/private/icon.ss) to use the new thread safe stuff is the right thing. Robby On Mon, Nov 16, 2009 at 7:36 PM, Eli Barzilay wrote: > On Nov 16, Carl Eastlund wrote: >> I got the following error while trying to modify the way Dracula uses >> check-expect tests: >> >> force: reentrant promise gc-on-bitmap >> [...] >> >> I don't think anything I did should cause this, but I'm not sure >> quite what happened so I can't say for sure. I do know my program >> had two check-expect tests, and when this error showed up the >> check-expect output displayed three results (my first test once and >> my second test twice). >> >> Does anyone know what might be causing this? > > This error happens when a promise is forced while it is forced. For > example: > > -> (define p (delay (force p))) > -> (force p) > force: reentrant promise p > > This is especially tricky when multiple threads are involved: > > -> (define p (delay (sleep 5))) > -> (thread (lambda () (force p))) > # > -> (force p) > force: reentrant promise p > > which could be a problem since threads are involved. > > As for what Robby said -- I comitted some major extension to > `scheme/promise', but the plain `delay'/`force'/`lazy' should be doing > exactly the same thing they did before, so no *new* problems should be > introduced. > > So, what I think you should do now is: > > 1. Try to undo my changes to `scheme/promise' and see if you get the > same error. You can just use the contents of the file from 4.2.2 > for this. If it doesn't fail, then there might be a bug in the > extension, and I'll need some minimal-ish code that reproduces it. > > 2. But I think that it's likely it will fail too. In that case, > you're probably running against the thread problem that I've > demonstrated above. (If you look at your stack trace, you'll see > that there is one `force/generic', which is what you'd get from my > thread example, but the first one will have two.) > > The good news is that one of the new extensions that I added is > `delay/sync' -- this is a kind of a promise that can be forced from > multiple threads, the first one will compute it and the rest will > block until it's ready. So, if it does fail, you should look > around for code that uses `delay'/`force', and see if you can fix > it by using `delay/sync'. > > BTW, this restriction that makes plain promises less useful with > multiple threads is relatively new (since v4). The older version > wouldn't throw that error -- but it would have the obvious race > conditions, which means that the promise will be forced multiple time, > and one will get to stay. > > -- > ((lambda (x) (x x)) (lambda (x) (x x))) Eli Barzilay: > http://barzilay.org/ Maze is Life! > _ > For list-related administrative tasks: > http://list.cs.brown.edu/mailman/listinfo/plt-dev > _ For list-related administrative tasks: http://list.cs.brown.edu/mailman/listinfo/plt-dev
Re: [plt-dev] Error message from test-engine
On Nov 16, Robby Findler wrote: > The promise in question has been there for a very long time (10+ > years, I'd guess), but there definitely could be treading problems. > Perhaps just changing (in framework/private/icon.ss) to use the new > thread safe stuff is the right thing. Yes, I've looked at them -- and they seem to be promises of the kind that would just lead (in pre-v4 days) to more work. But perhaps there was no problem until Carl somehow arranged things in a certain way. -- ((lambda (x) (x x)) (lambda (x) (x x))) Eli Barzilay: http://barzilay.org/ Maze is Life! _ For list-related administrative tasks: http://list.cs.brown.edu/mailman/listinfo/plt-dev
Re: [plt-dev] Error message from test-engine
On Mon, Nov 16, 2009 at 9:13 PM, Eli Barzilay wrote: > On Nov 16, Robby Findler wrote: >> The promise in question has been there for a very long time (10+ >> years, I'd guess), but there definitely could be treading problems. >> Perhaps just changing (in framework/private/icon.ss) to use the new >> thread safe stuff is the right thing. > > Yes, I've looked at them -- and they seem to be promises of the kind > that would just lead (in pre-v4 days) to more work. But perhaps there > was no problem until Carl somehow arranged things in a certain way. Using delay/sync for the framework icons seemed to alleviate the bug. I have committed this change. --Carl _ For list-related administrative tasks: http://list.cs.brown.edu/mailman/listinfo/plt-dev
Re: [plt-dev] Error message from test-engine
Thanks. Robby On Mon, Nov 16, 2009 at 9:43 PM, Carl Eastlund wrote: > On Mon, Nov 16, 2009 at 9:13 PM, Eli Barzilay wrote: >> On Nov 16, Robby Findler wrote: >>> The promise in question has been there for a very long time (10+ >>> years, I'd guess), but there definitely could be treading problems. >>> Perhaps just changing (in framework/private/icon.ss) to use the new >>> thread safe stuff is the right thing. >> >> Yes, I've looked at them -- and they seem to be promises of the kind >> that would just lead (in pre-v4 days) to more work. But perhaps there >> was no problem until Carl somehow arranged things in a certain way. > > Using delay/sync for the framework icons seemed to alleviate the bug. > I have committed this change. > > --Carl > _ For list-related administrative tasks: http://list.cs.brown.edu/mailman/listinfo/plt-dev
