A file picker and an alert can be shown at the same time, making the window unresponsive

👁 Image	Ben Bucksch (:BenB) Reporter
	Description • 14 years ago

I am currently in a situation where I cannot close the native file picker dialog that opens for a <input type="file"> element on a webpage. I can use the dialog just fine, it's working, just the "Cancel" and "Open" buttons have no effect. I can still use other Firefox windows, luckily, but I cannot access the Firefox window that opened the dialog, I cannot close that Firefox window either. I am stuck. I had pressed the "Open" button of the dialog before. The webpage, in the background, was opening an alert() (apparently) that shows an error message from the web app. This might be what is causing the deadlock. I see nothing relevant on the error console. The web app is the admin frontend of a phone system (gigaset IP).

👁 Image	Ben Bucksch (:BenB) Reporter
	Comment 1 • 14 years ago

👁 Image	Boris Zbarsky [:bzbarsky]
	Comment 2 • 14 years ago

This has nothing to do with form submission; it sounds like an OS-specific event delivery issue...

👁 Image	Ben Bucksch (:BenB) Reporter
	Comment 3 • 14 years ago

In case you need me to check something, I still have the window open, but I'll have to close it some time.

👁 Image	Mounir Lamouri (:mounir)
	Comment 4 • 14 years ago

I managed to create a testcase for it. Would be nice to have someone reproducing that on Windows or MacOS X to check if that's really platform specific.

👁 Image	Mounir Lamouri (:mounir)
	Updated • 14 years ago

👁 Image	Mounir Lamouri (:mounir)
	Updated • 14 years ago

👁 Image	Mounir Lamouri (:mounir)
	Comment 5 • 14 years ago

Actually, it breaks MacOS X and GTK but not Windows... and the way it breaks on MacOS X is different than GTK: the alert is never shown and the application is hanging when you click on OK or CANCEL.

👁 Image	Alice0775 White
	Comment 6 • 14 years ago

FYI If I set prompts.tab_modal.enabled to false, Browser does not hang on Nightly 8.0a1 of Windows and Linux.(not testing on MacOS)

👁 Image	Pierre Réveillon
	Comment 7 • 14 years ago

Isn't it the same bug as #476541?

👁 Image	Pierre Réveillon
	Comment 8 • 14 years ago

Soory for the missing link, it's bug 476541.

👁 Image	Mounir Lamouri (:mounir)
	Comment 9 • 14 years ago

(In reply to Pierre Réveillon from comment #7) > Isn't it the same bug as #476541? On Mac yes. But it seems like it's reproducible using the GTK widget. We could make this GTK though.

👁 Image	Mounir Lamouri (:mounir)
	Updated • 14 years ago

👁 Image	Ben Bucksch (:BenB) Reporter
	Comment 10 • 14 years ago

Per comment 2, back to GTK

👁 Image	Ben Bucksch (:BenB) Reporter
	Updated • 14 years ago

👁 Image	Karl Tomlinson (:karlt) Assignee
	Comment 11 • 14 years ago

Nested event loops are evil, and multiple nested event loops are more evil (if there is such a thing). The bug is in the nsIFilePicker::show interface because the "show" method can't return until it knows what the user selects. That means that either the whole application needs pause while waiting for the response or the "show" implementation needs to run a nested event loop. Further gtk_dialog_run doesn't hide the modal window. It is not closed until gtk_dialog_run returns which will not happen until the nested event loop exits. The tab-modal alert is implemented with another nested event loop. That means that the gtk_dialog_run nested event loop can't return until the tab-modal alert is dismissed. The modal dialog prevents the tab-modal alert from being dismissed. We could adjust the GTK nsIFilePicker implementation to hide the dialog when the buttons are pressed (instead of waiting for the event loop to exit), but there would still be a bug: The file would not be selected until the tab-modal alert has been dismissed. Bug 729720 comment 4 also wanted to make the filepicker interface async.

👁 Image	Karl Tomlinson (:karlt) Assignee
	Comment 12 • 14 years ago

A similar bug exists on Win7, although there is a race condition. If the file picker opens before the alert, then the file picker can be dismissed and then the alert. However, sometimes the file picker does not open but the window with the alert becomes unresponsive.

👁 Image	Karl Tomlinson (:karlt) Assignee
	Comment 13 • 14 years ago

Steven's work in bug 729720 comment 26 would go a long way in helping here.

👁 Image	Ben Bucksch (:BenB) Reporter
	Comment 14 • 14 years ago

Thanks for the reference, but I saw the bug on GTK.

👁 Image	Karl Tomlinson (:karlt) Assignee
	Comment 15 • 14 years ago

Part of Steven's patchset is cross platform to provide an async show() method.

👁 Image	Mounir Lamouri (:mounir)
	Comment 16 • 14 years ago

I think this bug should depend on bug 731307 instead.

👁 Image	Alice0775 White
	Updated • 14 years ago

👁 Image	Gábor Stefanik
	Comment 17 • 14 years ago

Isn't this security-sensitive?

👁 Image	Mounir Lamouri (:mounir)
	Comment 18 • 13 years ago

Those bugs where "sec:dos" before. How should they be marked now Jesse?

👁 Image	Jesse Ruderman
	Comment 19 • 13 years ago

Keep using [sg:dos] for now. We might add a csec-dos keyword eventually.

👁 Image	Ben Bucksch (:BenB) Reporter
	Updated • 13 years ago

👁 Image	Mounir Lamouri (:mounir)
	Comment 20 • 13 years ago

This should have been fixed by bug 731307. Might be nice if that could be checked by QA using the latest Nightly.

👁 Image	Karl Tomlinson (:karlt) Assignee
	Comment 21 • 13 years ago

Bug 731307 added suitable API, and moves the nested event loop to run off an event, but, to fix the bug, we still need to not wait for the nested event loop to return.

👁 Image	Karl Tomlinson (:karlt) Assignee
	Comment 22 • 13 years ago

Even the sync Show() variant doesn't demonstrate this lock-up any longer due to closing the window before waiting for the stack to unwind, but that method still has other bugs related to not unwinding the stack. gtk_window_set_destroy_with_parent is used to release the nsIFilePickerShownCallback (for the async variant) before XPCOM shutdown, when quitting from another window while the file dialog is still open. (That is the only reason the "destroy" handler is required.) The file picker would be of limited use without a parent anyway.

👁 Image	Robert O'Callahan (:roc) (email my personal email if necessary)
	Comment 23 • 13 years ago

Comment on attachment 654062 [details] [diff] [review] implement async nsIFilePicker::Open and make sync Show close window on response Review of attachment 654062 [details] [diff] [review]: ----------------------------------------------------------------- cool! ::: widget/gtk2/nsFilePicker.cpp @@ +377,5 @@ > + nsresult rv = Open(nullptr); > + if (NS_FAILED(rv)) > + return rv; > + > + while(mRunning) { space before ( ::: widget/xpwidgets/nsBaseFilePicker.cpp @@ +101,5 @@ > nsCOMPtr<nsIRunnable> filePickerEvent = > new AsyncShowFilePicker(this, aCallback); > return NS_DispatchToMainThread(filePickerEvent); > } > +#endif Do we really need these #ifdefs? Seems to me we don't.

👁 Image	Karl Tomlinson (:karlt) Assignee
	Comment 24 • 13 years ago

The ifdefs were to help clarify which code in the override hierarchy actually gets used, but dead code is generally left in the build, so followed style there. https://hg.mozilla.org/integration/mozilla-inbound/rev/d066131af975 There was a single try build here: https://tbpl.mozilla.org/?tree=Try&rev=6bcd619f0b76 It is hard to test this as it is difficult to send events to native dialogs.

👁 Image	Ed Morley [:emorley]
	Comment 25 • 13 years ago

👁 Image	Merih Akar
	Comment 26 • 13 years ago

The bug appears to be fixed in FF17, however I am currently using FF17 and the test page above still blocks the entire window. Am I missing something?

👁 Image	Karl Tomlinson (:karlt) Assignee
	Updated • 12 years ago

👁 Image	Robert O'Callahan (:roc) (email my personal email if necessary)
	Updated • 10 years ago