Bug#898468: debian-installer: black screen/long delay in graphical installer after switching from linux 4.15 to 4.16

Ben Hutchings ben at decadent.org.uk
Tue Jun 5 19:30:22 BST 2018

On Tue, 2018-06-05 at 19:20 +0200, Cyril Brulebois wrote:
> Hi,
> Ben Hutchings <ben at decadent.org.uk> (2018-05-13):
> > This sounds similar to the regression seen in stable affecting gnome-
> > session.  libICE has a function for generating the MIT-MAGIC-COOKIE-1
> > cookie, which now uses libbsd's arc4random_buf() which now uses
> > getrandom().  getrandom() is documented to block (by default) when not
> > much entropy is available, but until recently it could return too early
> > after boot.
> > 
> > I don't know whether the cookie is generated this way when d-i starts
> > the X server.
> > 
> > I opened bug #898088 against libbsd because arc4random_buf() is
> > documented to return "very quickly".
> Many thanks for the initial pointer and the libbsd bugfix. Unfortunately
> that wasn't our issue at all (we don't use libICE and there's no udeb
> for it anyway). I've documented my findings in a blog post:
>   https://debamax.com/blog/2018/05/25/debugging-black-screen-in-debian-installer/
> Summary: The issue is rather that we have fontconfig needing UUIDs for
> font handling, calling uuid_generate_random() from util-linux, which
> uses getrandom(), trying a few times with a little delay between each
> attempts when EAGAIN has been returned, before finally falling back to
> reading from /dev/{u,}random.

plymouth had the same problem, fixed in version 0.9.3-3.  You should be
able to avoid it by running fc-cache as part of the initramfs build


Ben Hutchings
Larkinson's Law: All laws are basically false.
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