Bug#639837: UI hangs for 30s while loading pages

[Greg Smith]

Sorry about not being threaded properly to existing discussion, I just 
joined this list.  I've been fighting the same problem Luc Maisonobe has 
been posting about here, been bothering me for a few months now.  I 
started seeing these >30 second hangs ever since upgrading to IceWeasel 
8.0, and they've continued to haunt me (on two systems) through upgrades 
to 9.0 and the current 10.0.1 I am running right now.  Lack of this 
problem on a stock Firefox installed in parallel proved to me it was 
something specific to the Iceweasel install.  Until today I didn't know 
what though.  Now I do:  it's the Shockwave/Flash plug-in in my case.

This turned 100% reproducible for me this morning, starting from 
clicking on an e-mail URL and then entering youtube.com as my next 
site.  Any variation on that--trying to start IceWeasel via command line 
for example--and it doesn't happen.  I've gotten lots of practice 
remembering exactly what order I did things in while trying to squash this.

As seen via strace, loading the youtube page freezes like this (same 
spot as Luc's example):

futex(0x7fbe2d7f3d8c, FUTEX_WAIT_BITSET_PRIVATE|FUTEX_CLOCK_REALTIME, 3, 
{1329219709, 44492000}, ffffffff

[Hangs here for >30 seconds]

) = -1 ETIMEDOUT (Connection timed out)

And then it finishes loading.  I have multiple strace dumps showing the 
same pattern here if anyone wants to see them.

After several rounds of isolating out what in my settings might be to 
blame, I discovered the problem comes and goes based on whether the 
Shockwave Flash Plugin is loaded.  With Shockwave Flash 10.3 d162 
enabled, and all other plug-ins/extensions disabled, I can reproduce the 
hang every time here now.  Disable that plugin and the hangs have gone 
away for me, even if then turn back on every other plugin and extension.

Some reading about possible causes here let me to 
http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=579659 which talks 
about concurrent DSP problems.  I checked my /etc/iceweasel/iceweaselrc 
and it has this:

ICEWEASEL_DSP="none"

Which seems to be the correct workaround for that problem.