521431 - Firefox locks up when displaying nested divs with small height and scrollbars

Status: RESOLVED WORKSFORME

(Core :: Layout, defect)

Description

[Tyler Bannister]

User-Agent:       Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.9.1.3) Gecko/20090910 Ubuntu/9.04 (jaunty) Shiretoko/3.5.3
Build Identifier: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.9.1.3) Gecko/20090910 Ubuntu/9.04 (jaunty) Shiretoko/3.5.3

While creating a web form, I made a small mistake in my form that caused Firefox to hang.  I've stripped the original file down to what appears to be a minimal test case that causes Firefox to hang.  All that's required is a series of nested divs that each have scrolling enabled and a small height.

Reproducible: Always

Steps to Reproduce:
1.Open the attached test case

Actual Results:  
Firefox becomes unresponsive and uses 100% of cpu.

Expected Results:  
Displayed a web page.

Also confirmed with Mozilla/5.0 (WindowsX11; U; Windows NT 5.1; en-GB; rv:1.9.1.3) Gecko/20090824 Firefox 3.5.3 Shiretoko/3.5.3 (.NET CLR 3.5.30729)

Comment 1

[Tyler Bannister]

Attachment: HTML test case that causes Firefox to hang.

If Firefox doesn't crash for you with this test case, you may want to try doubling the number of nested divs in it.  I found if I reduced the number of divs down to 5, firefox only hung for a short time and then became responsive again.

Comment 2

[Tyler Downer [He/Him]]

Yeah, nasty. Mozilla/5.0 (Windows; U; Windows NT 6.1; en-US; rv:1.9.3a1pre) Gecko/20091009 Minefield/3.7a1pre (.NET CLR 3.5.30729) ID:20091009051317 shows this.

Comment 3

[Henri Sivonen (:hsivonen) (temporarily away from Bugzilla)]

Guessing layout instead of parser.

Comment 4

[Boris Zbarsky [:bzbarsky]]

Presumably due to the multiple reflows that scrollframe does.  The innermost div here will get reflowed at least 1024 times, right?

Comment 5

[Robert O'Callahan (:roc) (email my personal email if necessary)]

Presumably that's what's happening, but we might be able to avoid it by memoizing some information about the scrolled child (what height it wants with/without a horizontal scrollbar present).

Comment 6

[Boris Zbarsky [:bzbarsky]]

Sounds good to me...

Comment 7

[Andrei Purice]

Marking this as Resolved > Worksforme since the issue is no longer reproducible on Firefox Nightly 96.0a1 (2021-11-04), beta 95.0b2 or release 94.0 on Windows 10 and MacOS 11.6.
If anyone can still reproduce this issue please re-open it or file a new one.