Re: [PATCH v2 5/9] Move buildchroot mounts into dpkg-base class

[Alexander Smirnov <asmirnov@ilbers.de>]

Jan Kiszka <jan.kiszka@siemens.com> 13 февраля 2018 г. 23:48:02 написал:

> On 2018-02-13 21:17, Alexander Smirnov wrote:
>>
>>
>> On 02/13/2018 11:05 PM, Jan Kiszka wrote:
>>> From: Jan Kiszka <jan.kiszka@siemens.com>
>>>
>>> This avoids the unfortunate setup_mounts task which is either not
>>> executed on rebuilds or causes excessive package rebuilds. We just need
>>> ensure prior to switching into the buildchroot that all mount points are
>>> populated.
>>>
>>> Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
>>> ---
>>>   meta/classes/dpkg-base.bbclass                   | 13 +++++++++-
>>>   meta/recipes-devtools/buildchroot/buildchroot.bb | 30
>>> +++---------------------
>>>   2 files changed, 15 insertions(+), 28 deletions(-)
>>>
>>> diff --git a/meta/classes/dpkg-base.bbclass
>>> b/meta/classes/dpkg-base.bbclass
>>> index a45fbce..66132da 100644
>>> --- a/meta/classes/dpkg-base.bbclass
>>> +++ b/meta/classes/dpkg-base.bbclass
>>> @@ -2,7 +2,7 @@
>>>   # Copyright (C) 2017 Siemens AG
>>>     # Add dependency from buildchroot creation
>>> -do_build[depends] = "buildchroot:do_setup_mounts"
>>> +do_build[depends] = "buildchroot:do_build"
>>>     # Add dependency between Isar recipes
>>>   DEPENDS ?= ""
>>> @@ -20,11 +20,22 @@ dpkg_runbuild() {
>>>       die "This should never be called, overwrite it in your derived
>>> class"
>>>   }
>>>   +mount_if_needed() {
>>> +
>>> +    # The test may race with parallel builds. So probe, mount if
>>> needed, and
>>> +    # then only fail if both the mount and yet another probe failed
>>> as well.
>>> +    grep -q $2 /proc/mounts || sudo mount $1 $2 || grep -q $2
>>> /proc/mounts
>>
>> This could lead to have lots of remounts on the same folder during
>> parallel execution. This should be done in a separate task and protected
>> by [lockfiles].
>
> No, it won't - please re-read the code. It's a classic retry pattern,
> and it's even detecting errors.
>

'mount --bind' never fails. So if several do_build() have passed first grep 
in parallel, then each one will mount 'isar-apt'. Or I don't understand this.

Alex

> Jan
>
> --
> Siemens AG, Corporate Technology, CT RDA IOT SES-DE
> Corporate Competence Center Embedded Linux
--
With best regards,
Alexander Smirnov

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