[PATCH 1/1] isar-apt: fix race-condition in do_cache_config

[PATCH 1/1] isar-apt: fix race-condition in do_cache_config

['Felix Moessbauer' via isar-users]

Repo configuration operations on the isar apt have to happen while
holding the isar lock. However, bitbake executes the cleandirs operation
without holding the lock, introducing a race-condition that sporadically
breaks the build with the following error:

  Error opening config file '/isar/build/tmp/deploy/isar-apt/
  debian-trixie/apt/debian-trixie/conf/distributions': No such file
  or directory(2)

We fix this by open-coding the cleandirs logic inside the function and
by that under the lock.

Fixes: be290896 ("isar-apt: support further optional fields ...")
Signed-off-by: Felix Moessbauer <felix.moessbauer@siemens.com>
---
Note, that I was able to reliably produce this with the sbom test:
./scripts/run-tests.sh -t sbom

Best regards,
Felix

 meta/recipes-devtools/isar-apt/isar-apt.bb | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/meta/recipes-devtools/isar-apt/isar-apt.bb b/meta/recipes-devtools/isar-apt/isar-apt.bb
index e824bf1d..4ecbdb82 100644
--- a/meta/recipes-devtools/isar-apt/isar-apt.bb
+++ b/meta/recipes-devtools/isar-apt/isar-apt.bb
@@ -10,11 +10,15 @@ SRC_URI = "file://distributions.in"
 
 do_cache_config[lockfiles] = "${REPO_ISAR_DIR}/isar.lock"
 do_cache_config[vardeps] += "ISAR_APT_OPT_FIELD"
-do_cache_config[cleandirs] += "${REPO_ISAR_DIR}/${DISTRO}/conf"
 
 # Generate reprepro config for current distro if it doesn't exist. Once it's
 # generated, this task should do nothing.
 do_cache_config() {
+    # this part must be executed while holding the isar.lock, hence do not move
+    # it to cleandirs (these are executed without holding the lock)
+    rm -rf ${REPO_ISAR_DIR}/${DISTRO}/conf
+    mkdir -p ${REPO_ISAR_DIR}/${DISTRO}/conf
+
     repo_create "${REPO_ISAR_DIR}"/"${DISTRO}" \
         "${REPO_ISAR_DB_DIR}"/"${DISTRO}" \
         "${DEBDISTRONAME}" \
-- 
2.53.0

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Re: [PATCH 1/1] isar-apt: fix race-condition in do_cache_config

['MOESSBAUER, Felix' via isar-users]

On Wed, 2026-06-03 at 13:46 +0200, Felix Moessbauer wrote:
> Repo configuration operations on the isar apt have to happen while
> holding the isar lock. However, bitbake executes the cleandirs operation
> without holding the lock, introducing a race-condition that sporadically
> breaks the build with the following error:
> 
>   Error opening config file '/isar/build/tmp/deploy/isar-apt/
>   debian-trixie/apt/debian-trixie/conf/distributions': No such file
>   or directory(2)
> 
> We fix this by open-coding the cleandirs logic inside the function and
> by that under the lock.
> 
> Fixes: be290896 ("isar-apt: support further optional fields ...")

PS: Commit "Revert "Split up isar-apt into distro-arch specific
instances" probably made it much more likely to run into the race-
condition, but the race was there before.

Felix

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Re: [PATCH 1/1] isar-apt: fix race-condition in do_cache_config

[Anton Mikanovich]

03.06.2026 14:56, 'MOESSBAUER, Felix' via isar-users wrote:
> PS: Commit "Revert "Split up isar-apt into distro-arch specific
> instances" probably made it much more likely to run into the race-
> condition, but the race was there before.
>
> Felix
>
Hello Felix,

Thanks for the fix.
It looks like the patch is working, but on the full CI other issue observed.
Don't think it is related, but rechecking will take some time.

Just in case, here is the failure during do_rootfs_install task of
isar-image-base recipe for virtualbox-bullseye target:

dpkg: error processing archive 
/tmp/apt-dpkg-install-rJzE6r/16-example-raw_0.3_all.deb (--unpack):
cannot access archive 
'/tmp/apt-dpkg-install-rJzE6r/16-example-raw_0.3_all.deb': No such file 
or directory

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Re: [PATCH 1/1] isar-apt: fix race-condition in do_cache_config

[Anton Mikanovich]

04.06.2026 12:39, Anton Mikanovich wrote:
> Hello Felix,
>
> Thanks for the fix.
> It looks like the patch is working, but on the full CI other issue 
> observed.
> Don't think it is related, but rechecking will take some time.
>
> Just in case, here is the failure during do_rootfs_install task of
> isar-image-base recipe for virtualbox-bullseye target:
>
> dpkg: error processing archive 
> /tmp/apt-dpkg-install-rJzE6r/16-example-raw_0.3_all.deb (--unpack):
> cannot access archive 
> '/tmp/apt-dpkg-install-rJzE6r/16-example-raw_0.3_all.deb': No such 
> file or directory
>
Ok, I've found the reason of one more race in do_rootfs_install:
Apt-get don't cache debs from isar-apt (because of file:// scheme) to
/var/cache/apt/archives, so our isar-apt locking on 
rootfs_install_pkgs_download
don't really work.
Will merge this fix and prepare the next fix for do_rootfs_install soon.

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Re: [PATCH 1/1] isar-apt: fix race-condition in do_cache_config

[Anton Mikanovich]

03.06.2026 14:46, 'Felix Moessbauer' via isar-users wrote:
> Repo configuration operations on the isar apt have to happen while
> holding the isar lock. However, bitbake executes the cleandirs operation
> without holding the lock, introducing a race-condition that sporadically
> breaks the build with the following error:
>
>    Error opening config file '/isar/build/tmp/deploy/isar-apt/
>    debian-trixie/apt/debian-trixie/conf/distributions': No such file
>    or directory(2)
>
> We fix this by open-coding the cleandirs logic inside the function and
> by that under the lock.
>
> Fixes: be290896 ("isar-apt: support further optional fields ...")
> Signed-off-by: Felix Moessbauer <felix.moessbauer@siemens.com>
Applied to next, thanks.

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