Re: [PATCH v2] dpkg: acquire a read (shared) locks while building packages

["Maxim Yu. Osipov" <mosipov@ilbers.de>]

On 3/8/19 4:49 PM, Cedric Hombourger wrote:
> As debhelper scripts involved during the actual build process
> (dpkg-buildpackage) may access the dpkg database, we need to
> make sure it does not get modified in the background by other
> build tasks for other packages (such as install_build_deps).
> An example of a reader is dh_shlibdeps/dpkg-shlibdeps: it
> needs to find packages providing the shared libraries the
> package depends on to substitute shlibs variables found in its
> control file with package dependencies. Acquire the isar-apt
> lock as a shared lock to block writers.
> 
> Special care may be needed in other classes/users of the
> dpkg_runbuild API. Due to some limitations with bitbake (to be
> discussed with the maintainers), we could not grab the lock
> from dpkg-base. A statement such as "flock <my-lock.lock>
> dpkg_run_build" would fail as flock can't exec() dpkg_run_build
> (since it is a shell function, not an executable). The popular
> shell construct "( flock -n 9; dpkg_run_build ) 9> <my-lock.lock>"
> cannot be parsed by bitbake. And finally the lockfiles task
> attribute (implemented in bitbake) only handles exclusive locks.
> 
> This commit is only addressing dpkg.bbclass. dpkg-raw.bbclass
> is left intact as the generated control file does require
> dh_shlibdeps. linux-custom.inc was also left out as the Debian
> packaging scripts only use low-level packaging tools and do not
> use debhelper scripts during packaging (at this time). In
> agreement with the Isar project maintainers, we will not grab
> the Isar lock from linux-custom.inc to let kernel builds run
> in parallel with do_install_deps() and do_deploy_deb() that
> may be executed by other bitbake threads.

Applied to the 'next'.

Thanks,
Maxim.

> Signed-off-by: Cedric Hombourger <Cedric_Hombourger@mentor.com>
> ---
>   meta/classes/dpkg.bbclass | 1 +
>   1 file changed, 1 insertion(+)
> 
> diff --git a/meta/classes/dpkg.bbclass b/meta/classes/dpkg.bbclass
> index 24b9fe3..f4e3d7a 100644
> --- a/meta/classes/dpkg.bbclass
> +++ b/meta/classes/dpkg.bbclass
> @@ -19,5 +19,6 @@ do_install_builddeps[stamp-extra-info] = "${DISTRO}-${DISTRO_ARCH}"
>   # Build package from sources using build script
>   dpkg_runbuild() {
>       E="${@ bb.utils.export_proxies(d)}"
> +    flock -s "${REPO_ISAR_DIR}/isar.lock" \
>       sudo -E chroot --userspec=$( id -u ):$( id -g ) ${BUILDCHROOT_DIR} /isar/build.sh ${PP}/${PPS} ${DISTRO_ARCH}
>   }
> 


-- 
Maxim Osipov
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