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 11:07 AM, Dragos-Marian Panait wrote:
>
>
> 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


Sorry for adding to the confusion. My point was intended to be that I am 
fairly certain the recent patch submitted by Khem will resolve the boot 
delay issue you are having as well as the original boot delay caused by 
systemd-udev-settle.

Drew

-- 
mailto:drew@moseleynet.net

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