[PATCH 1/4] fix(dpkg-build): make sstate updates of DEPLOY_DIR_DEB atomic

["'Felix Moessbauer' via isar-users" <isar-users@googlegroups.com>]

DEPLOY_DIR_DEB is qualified by DISTRO, DISTRO_ARCH and PN, but not by
MACHINE. All multiconfigs sharing DISTRO and DISTRO_ARCH therefore run
do_dpkg_build and do_deploy_deb of the very same recipe on one directory,
concurrently and without any mutual exclusion. testsuite's test_cross for
example builds mc:qemuarm-bookworm and mc:nanopi-neo-efi-bookworm, both
armhf, so both provide hello-isar and example-module-armmp.

sstate_clean() unlinks the debs listed in the manifest before
sstate_install() puts them back. A do_deploy_deb running in parallel can
therefore observe DEPLOY_DIR_DEB partially populated, remove exactly the
packages that are still there from isar-apt and add back only those, so
the remaining ones silently disappear from the repository.

Take a dedicated lock in both sstate_clean() and sstate_install() of
do_dpkg_build, and in do_deploy_deb, via the sstate-lockfile task flag.
DEPLOY_DIR_DEB is then either complete or empty for do_deploy_deb, never
partial. The lock lives next to, not inside, DEPLOY_DIR_DEB so that
sstate_clean_manifest() cannot sweep it away.

Fixes: 1182a45b ("fix(dpkg-build): deploy debs via shared sstate dir")
Signed-off-by: Felix Moessbauer <felix.moessbauer@siemens.com>
---
 meta/classes-recipe/dpkg-base.bbclass | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/meta/classes-recipe/dpkg-base.bbclass b/meta/classes-recipe/dpkg-base.bbclass
index 4a81787e..164f247e 100644
--- a/meta/classes-recipe/dpkg-base.bbclass
+++ b/meta/classes-recipe/dpkg-base.bbclass
@@ -18,6 +18,13 @@ inherit essential
 # WORKDIR lifecycle.
 DEPLOYDIR = "${WORKDIR}/deploy"
 DEPLOY_DIR_DEB = "${DEPLOY_DIR}/isar-deb/${DISTRO}-${DISTRO_ARCH}/${PN}"
+# DEPLOY_DIR_DEB is not qualified by MACHINE, so all multiconfigs sharing
+# DISTRO and DISTRO_ARCH run do_dpkg_build and do_deploy_deb of the same recipe
+# on it, concurrently. Serialize the sstate clean/install of do_dpkg_build
+# against do_deploy_deb, so that the latter never sees a partially populated
+# directory. Keep the lock next to, not inside, DEPLOY_DIR_DEB so that
+# sstate_clean_manifest() cannot sweep it away.
+DEPLOY_DIR_DEB_LOCK = "${DEPLOY_DIR}/isar-deb/${DISTRO}-${DISTRO_ARCH}/${PN}.lock"
 
 DEPENDS ?= ""
 RPROVIDES ?= "${PROVIDES}"
@@ -207,6 +214,7 @@ python do_dpkg_build() {
 do_dpkg_build[cleandirs] = "${DEPLOYDIR}"
 do_dpkg_build[sstate-inputdirs] = "${DEPLOYDIR}"
 do_dpkg_build[sstate-outputdirs] = "${DEPLOY_DIR_DEB}"
+do_dpkg_build[sstate-lockfile] = "${DEPLOY_DIR_DEB_LOCK}"
 do_dpkg_build[network] = "${TASK_USE_NETWORK_AND_SUDO}"
 do_dpkg_build[depends] = "${SCHROOT_DEP} base-apt:do_cache isar-apt:do_cache_config"
 do_dpkg_build[postfuncs] += "dpkg_collect_debs"
@@ -232,7 +240,9 @@ deb_clean() {
         done
     fi
 }
-# the clean function modifies isar-apt
+# the clean function modifies isar-apt. Do not add DEPLOY_DIR_DEB_LOCK here:
+# CLEANFUNCS also runs sstate_cleanall(), which takes that lock itself, and
+# flock() would deadlock on the nested acquisition.
 do_clean[lockfiles] = "${REPO_ISAR_DIR}/isar.lock"
 do_clean[network] = "${TASK_USE_SUDO}"
 
@@ -249,7 +259,7 @@ addtask deploy_deb after do_dpkg_build before do_build
 do_deploy_deb[deptask] = "do_deploy_deb"
 do_deploy_deb[rdeptask] = "do_deploy_deb"
 do_deploy_deb[depends] += "isar-apt:do_cache_config"
-do_deploy_deb[lockfiles] = "${REPO_ISAR_DIR}/isar.lock"
+do_deploy_deb[lockfiles] = "${REPO_ISAR_DIR}/isar.lock ${DEPLOY_DIR_DEB_LOCK}"
 do_deploy_deb[dirs] = "${S} ${DEPLOY_DIR_DEB}"
 
 python do_devshell() {
-- 
2.55.0

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