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Re: lightdm (testing): Long waiting time after login

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On 17.05.2018 00:43 Ben Caradoc-Davies wrote:
> On 16/05/18 19:28, work@hllmnn.de wrote:
>> I just did a fresh install of testing with XFCE. After entering the 
>> login
>> credentials the screen was black for 30-60 seconds before the desktop
>> environment showed up. Assuming a bug in XFCE, I performed another 
>> fresh install
>> with MATE, but a similar effect occured: after login the background 
>> image is
>> shown for 30-60 seconds before the desktop is fully loaded.
>
> What happens if you wiggle your mouse or provide keyboard activity 
> while waiting? For example, if you wiggle your mouse vigorously for 
> two seconds or press the Alt key 20 times? Does the wait end sooner?
>
> In Linux 4.16, the getrandom system call (without the GRND_NONBLOCK 
> flag) blocks until sufficient entropy is available in the pool. This 
> is the documented behaviour, and Linux 4.16 now enforces it to fix 
> CVE-2018-1108. This has caught out several services that try to use 
> getrandom (without the GRND_NONBLOCK flag) at early boot, including 
> plymouth (via fontconfig) and gdm3. What you see might have the same 
> cause. For details of my investigation, see:
> https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=897572
>
> Wiggling your mouse or providing keyboard activity adds entropy to the 
> pool. If this reduces the waiting time, you might be affected by the 
> same bug.
>
> Kind regards,
>
Hi Ben,

Yes, you're right! When I wiggle the mouse the wait ends sooner. Indeed, 
if I don't move the mouse at all and don't press any key the screen just 
stays blank (I waited approx. 5 minutes and it still was black).

I attached the output of dmesg | grep "random". As you can see, "crng 
init done" appears after the 5 minutes I waited.

Since there is no "splash" in my kernel command line in grub, I added 
"noplymouth" to it, but that didn't help. Maybe it's another package 
that calls getrandom without GRND_NONBLOCK. Let me know if I can support 
the investigation somehow.

Kind regards,
Dino

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Re: lightdm (testing): Long waiting time after login Ben Caradoc-Davies <ben@transient.nz> - 2018-05-17 00:50 +0200
  Re: lightdm (testing): Long waiting time after login Dino <work@hllmnn.de> - 2018-05-17 11:10 +0200
    Re: lightdm (testing): Long waiting time after login Curt <curty@free.fr> - 2018-05-17 12:10 +0200
    Re: lightdm (testing): Long waiting time after login Ben Caradoc-Davies <ben@transient.nz> - 2018-05-18 01:10 +0200
      Re: lightdm (testing): Long waiting time after login Dino <work@hllmnn.de> - 2018-05-18 08:50 +0200
        Re: lightdm (testing): Long waiting time after login songbird <songbird@anthive.com> - 2018-05-18 12:10 +0200
          Re: lightdm (testing): Long waiting time after login Dino <work@hllmnn.de> - 2018-05-18 16:00 +0200
            Re: lightdm (testing): Long waiting time after login Ben Caradoc-Davies <ben@transient.nz> - 2018-05-19 00:10 +0200
              Re: lightdm (testing): Long waiting time after login Ben Caradoc-Davies <ben@transient.nz> - 2018-05-19 01:30 +0200
                Re: lightdm (testing): Long waiting time after login Ben Caradoc-Davies <ben@transient.nz> - 2018-05-19 03:10 +0200
                Re: lightdm (testing): Long waiting time after login Ben Caradoc-Davies <ben@transient.nz> - 2018-05-21 05:30 +0200
                Re: lightdm (testing): Long waiting time after login Dino <work@hllmnn.de> - 2018-05-22 10:00 +0200
                Re: lightdm (testing): Long waiting time after login Ben Caradoc-Davies <ben@transient.nz> - 2018-05-23 00:50 +0200
                Re: lightdm (testing): Long waiting time after login Glenn English <ghe2001@gmail.com> - 2018-05-23 18:50 +0200
                Re: lightdm (testing): Long waiting time after login Ben Caradoc-Davies <ben@transient.nz> - 2018-05-24 00:20 +0200
                Re: lightdm (testing): Long waiting time after login Glenn English <ghe2001@gmail.com> - 2018-05-24 15:50 +0200
                Re: lightdm (testing): Long waiting time after login Ben Caradoc-Davies <ben@transient.nz> - 2018-05-25 00:30 +0200

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