Re: [OE-core][PATCH] rng-tools: Change "Requires" to "WantedBy" for dev-hwrng.device

["Drew Moseley" <drew.moseley@gmail.com>]

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On 8/19/22 8:50 AM, Dragos-Marian Panait wrote:
>
> Hi Claudius,
>
> On 19.08.2022 12:36, Claudius Heine wrote:
>> [Please note: This e-mail is from an EXTERNAL e-mail address]
>>
>> Hi Dew.
>>
>> On 2022-08-15 20:25, drew.moseley@gmail.com wrote:
>>> From: Drew Moseley <drew@moseleynet.net>
>>>
>>> The previous change to remove the dependency on systemd-udev-settle
>>> caused boot delays at least on qemu. It seems that change required
>>> a hwrng device but that's not necessarily available on all platforms.
>>>
>>> This changes the "Requires" to a "WantedBy" as modeled after the
>>> version of this file on Ubuntu 20.04.
>>>
>>> Signed-off-by: Drew Moseley <drew@moseleynet.net>
>>> ---
>>>   meta/recipes-support/rng-tools/rng-tools/rng-tools.service | 3 +--
>>>   1 file changed, 1 insertion(+), 2 deletions(-)
>>>
>>> diff --git 
>>> a/meta/recipes-support/rng-tools/rng-tools/rng-tools.service 
>>> b/meta/recipes-support/rng-tools/rng-tools/rng-tools.service
>>> index 0f50890dcb..b013d95932 100644
>>> --- a/meta/recipes-support/rng-tools/rng-tools/rng-tools.service
>>> +++ b/meta/recipes-support/rng-tools/rng-tools/rng-tools.service
>>> @@ -3,8 +3,6 @@ Description=Hardware RNG Entropy Gatherer Daemon
>>>   DefaultDependencies=no
>>>   After=systemd-udev-settle.service
>>>   Before=sysinit.target shutdown.target
>>> -Requires=dev-hwrng.device
>>> -After=dev-hwrng.device
>>>   Conflicts=shutdown.target
>>>
>>>   [Service]
>>> @@ -32,3 +30,4 @@ SystemCallFilter=@system-service
>>>
>>>   [Install]
>>>   WantedBy=sysinit.target
>>> +WantedBy=dev-hwrng.device
>>
>> This looses the order. Have you tried just replacing `Requires` with
>> `Wants`. So something like this:
>>
>>
>> ```
>>
>> Before=sysinit.target shutdown.target
>> Wants=dev-hwrng.device
>> After=dev-hwrng.device
>> Conflicts=shutdown.target
>>
>> ```
>>
>> If that still would cause the long waiting time on qemu?
>>
>> I haven't investigated the qemu issue, but maybe qemu just doesn't
>> provide a hardware random source? If it doesn't provide a hardware
>> random source, then installing rng-tools on there might also not make 
>> sense.
>> Alternatively maybe just adding a start timeout might solve it?
>> regards,
>> Claudius
>
>
> I've tested the patch on a NUC7, results are the same as with qemu:
> - increased boot time
> - timeout for rng-tools.service
> [ TIME ] Timed out waiting for device /dev/hwrng.
> [DEPEND] Dependency failed for Hard…e RNG Entropy Gatherer Daemon.
>
> Regards,
> Dragos
>

Interesting. I guess this patch should definitely be ignored and the 
patch from Khem that removes both the dev-hwrng and systemd-udev-settle 
depencies is the right approach. That means that the original problem 
that adding systemd-udev-settle was meant to solve, is no longer solved 
but it seems that the proposed solutions here have adverse effects 
elsewhere.

Simply removing the systemd-udev-settle dependency fixes the issue that 
my customer has that caused me to start investigating here.

Drew

-- 
mailto:drew@moseleynet.net

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