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

[Dragos-Marian Panait <dragos.panait@windriver.com>]

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On 19.08.2022 17:34, Drew Moseley wrote:
>
> **[Please note: This e-mail is from an EXTERNAL e-mail address]
>
>
> 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 
>>>> <https://urldefense.com/v3/__http://sysinit.target__;!!AjveYdw8EvQ!bMQ5MfvZXWSzWjMLcLKDiM6wYi4-aF2QLE3CUcAKrFyEDpC2HxgAIFZGkwbGAHCJ81Fwt4gLnBeDKIdmEXOhOUu8G5A$> 
>>>> shutdown.target 
>>>> <https://urldefense.com/v3/__http://shutdown.target__;!!AjveYdw8EvQ!bMQ5MfvZXWSzWjMLcLKDiM6wYi4-aF2QLE3CUcAKrFyEDpC2HxgAIFZGkwbGAHCJ81Fwt4gLnBeDKIdmEXOhfig0Hzw$> 
>>>>
>>>> -Requires=dev-hwrng.device
>>>> -After=dev-hwrng.device
>>>>   Conflicts=shutdown.target 
>>>> <https://urldefense.com/v3/__http://shutdown.target__;!!AjveYdw8EvQ!bMQ5MfvZXWSzWjMLcLKDiM6wYi4-aF2QLE3CUcAKrFyEDpC2HxgAIFZGkwbGAHCJ81Fwt4gLnBeDKIdmEXOhfig0Hzw$> 
>>>>
>>>>
>>>>   [Service]
>>>> @@ -32,3 +30,4 @@ SystemCallFilter=@system-service
>>>>
>>>>   [Install]
>>>>   WantedBy=sysinit.target 
>>>> <https://urldefense.com/v3/__http://sysinit.target__;!!AjveYdw8EvQ!bMQ5MfvZXWSzWjMLcLKDiM6wYi4-aF2QLE3CUcAKrFyEDpC2HxgAIFZGkwbGAHCJ81Fwt4gLnBeDKIdmEXOhOUu8G5A$> 
>>>>
>>>> +WantedBy=dev-hwrng.device
>>>
>>> This looses the order. Have you tried just replacing `Requires` with
>>> `Wants`. So something like this:
>>>
>>>
>>> ```
>>>
>>> Before=sysinit.target 
>>> <https://urldefense.com/v3/__http://sysinit.target__;!!AjveYdw8EvQ!bMQ5MfvZXWSzWjMLcLKDiM6wYi4-aF2QLE3CUcAKrFyEDpC2HxgAIFZGkwbGAHCJ81Fwt4gLnBeDKIdmEXOhOUu8G5A$> 
>>> shutdown.target 
>>> <https://urldefense.com/v3/__http://shutdown.target__;!!AjveYdw8EvQ!bMQ5MfvZXWSzWjMLcLKDiM6wYi4-aF2QLE3CUcAKrFyEDpC2HxgAIFZGkwbGAHCJ81Fwt4gLnBeDKIdmEXOhfig0Hzw$> 
>>>
>>> Wants=dev-hwrng.device
>>> After=dev-hwrng.device
>>> Conflicts=shutdown.target 
>>> <https://urldefense.com/v3/__http://shutdown.target__;!!AjveYdw8EvQ!bMQ5MfvZXWSzWjMLcLKDiM6wYi4-aF2QLE3CUcAKrFyEDpC2HxgAIFZGkwbGAHCJ81Fwt4gLnBeDKIdmEXOhfig0Hzw$> 
>>>
>>>
>>> ```
>>>
>>> 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
Sorry for the confusion, I did not test any additional patches/changes 
that have been suggested in this email thread.
My test was performed on current Yocto master sources. No additional 
patches.
I just wanted to inform that the boot delay is also observed on real hw, 
not just qemu.
Again, sorry for the confusion.

Dragos

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