[PATCH v2 3/3] fix race-cond between default and custom initrd

[Felix Moessbauer <felix.moessbauer@siemens.com>]

This patch fixes a data race happening when building a custom initrd.
Previously, both custom and default initrds were deployed to the image
deploy dir. The race is fixed by conditionally deploying either the
custom or the default one. For that, we introduce a new variable
INITRD_DEPLOY_FILE which provides the name of the initrd in the deploy
directory. The existing INITRD_IMAGE variable is defaulted to the empty
string and used to control if a custom initrd is requrested. Only if
this variable is empty, the default one is deployed.

Signed-off-by: Felix Moessbauer <felix.moessbauer@siemens.com>
---
 RECIPE-API-CHANGELOG.md    |  8 ++++++++
 meta/classes/image.bbclass | 20 ++++++++++++--------
 scripts/start_vm           |  4 ++--
 testsuite/start_vm.py      |  2 +-
 4 files changed, 23 insertions(+), 11 deletions(-)

diff --git a/RECIPE-API-CHANGELOG.md b/RECIPE-API-CHANGELOG.md
index e48c98c7..1e8dbfc8 100644
--- a/RECIPE-API-CHANGELOG.md
+++ b/RECIPE-API-CHANGELOG.md
@@ -476,3 +476,11 @@ Bitbake 2.0 for better performance. It also requires isar-sstate script to be
 migrated to zstd.
 Mixing old Gzip-based and new ZStandatd-based sstate cache is not recommended
 and should be avoid for correct compatibility.
+
+### Working with a custom initramfs
+
+The existing `INITRD_IMAGE` variable is defaulted to the empty string and used to
+control if a custom initrd is requrested. Only if this variable is empty, the
+default one is deployed. By that, the variable cannot be used to get the name of
+the images initramfs. Instead, the variable `INITRD_DEPLOY_FILE` is provided which
+always povides the name of the initrd file (also when the default one is used).
diff --git a/meta/classes/image.bbclass b/meta/classes/image.bbclass
index 6277069f..7b3551b0 100644
--- a/meta/classes/image.bbclass
+++ b/meta/classes/image.bbclass
@@ -23,7 +23,8 @@ IMAGE_FULLNAME = "${PN}-${DISTRO}-${MACHINE}"
 
 # These variables are used by wic and start_vm
 KERNEL_IMAGE ?= "${IMAGE_FULLNAME}-${KERNEL_FILE}"
-INITRD_IMAGE ?= "${IMAGE_FULLNAME}-initrd.img"
+INITRD_IMAGE ?= ""
+INITRD_DEPLOY_FILE = "${@ d.getVar('INITRD_IMAGE', True) or '${IMAGE_FULLNAME}-initrd.img'}"
 
 # This defines the deployed dtbs for reuse by imagers
 DTB_FILES ?= ""
@@ -353,7 +354,7 @@ EOF
 
 # Default kernel, initrd and dtb image deploy paths (inside imager)
 KERNEL_IMG = "${PP_DEPLOY}/${KERNEL_IMAGE}"
-INITRD_IMG = "${PP_DEPLOY}/${INITRD_IMAGE}"
+INITRD_IMG = "${PP_DEPLOY}/${INITRD_DEPLOY_FILE}"
 # only one dtb file supported, pick the first
 DTB_IMG = "${PP_DEPLOY}/${@(d.getVar('DTB_FILES').split() or [''])[0]}"
 
@@ -370,12 +371,15 @@ do_copy_boot_files() {
         sudo cat "$kernel" > "${DEPLOYDIR}/${KERNEL_IMAGE}"
     fi
 
-    initrd="$(realpath -q '${IMAGE_ROOTFS}/initrd.img')"
-    if [ ! -f "$initrd" ]; then
-        initrd="$(realpath -q '${IMAGE_ROOTFS}/boot/initrd.img')"
-    fi
-    if [ -f "$initrd" ]; then
-        cp -f "$initrd" '${DEPLOYDIR}/${INITRD_IMAGE}'
+    if [ -e "${INITRD_IMAGE}" ]; then
+        # deploy default initrd if no custom one is build
+        initrd="$(realpath -q '${IMAGE_ROOTFS}/initrd.img')"
+        if [ ! -f "$initrd" ]; then
+            initrd="$(realpath -q '${IMAGE_ROOTFS}/boot/initrd.img')"
+        fi
+        if [ -f "$initrd" ]; then
+            cp -f "$initrd" '${DEPLOYDIR}/${INITRD_DEPLOY_FILE}'
+        fi
     fi
 
     for file in ${DTB_FILES}; do
diff --git a/scripts/start_vm b/scripts/start_vm
index 17091d72..8c696a4a 100755
--- a/scripts/start_vm
+++ b/scripts/start_vm
@@ -125,10 +125,10 @@ case "$IMAGE_FSTYPES" in
     readonly ROOTFS_IMAGE=$IMAGE_FULLNAME.ext4
 
     eval $(bitbake -e mc:qemu$ARCH-$DISTRO:isar-image-base | grep "^KERNEL_IMAGE=")
-    eval $(bitbake -e mc:qemu$ARCH-$DISTRO:isar-image-base | grep "^INITRD_IMAGE=")
+    eval $(bitbake -e mc:qemu$ARCH-$DISTRO:isar-image-base | grep "^INITRD_DEPLOY_FILE=")
     QKERNEL=$IMAGE_DIR/${KERNEL_IMAGE}
     QINITRD=/dev/null
-    [ -n "$INITRD_IMAGE" ] && QINITRD=$IMAGE_DIR/${INITRD_IMAGE}
+    [ -n "$INITRD_DEPLOY_FILE" ] && QINITRD=$IMAGE_DIR/${INITRD_DEPLOY_FILE}
     if [ "$ARCH" = "riscv64" ]; then
         EXTRA_ARGS="$EXTRA_ARGS -device loader,file=$QKERNEL,addr=0x80200000"
         QKERNEL="/usr/lib/riscv64-linux-gnu/opensbi/qemu/virt/fw_jump.elf"
diff --git a/testsuite/start_vm.py b/testsuite/start_vm.py
index 82ecc17d..ba1ba127 100755
--- a/testsuite/start_vm.py
+++ b/testsuite/start_vm.py
@@ -35,7 +35,7 @@ def format_qemu_cmdline(arch, build, distro, out, pid, enforce_pcbios=False):
     if image_type == 'ext4':
         rootfs_image = 'isar-image-base-' + base + '-' + distro + '-qemu' + arch + '.ext4'
         kernel_image = deploy_dir_image + '/' + get_bitbake_var(bb_output, 'KERNEL_IMAGE')
-        initrd_image = get_bitbake_var(bb_output, 'INITRD_IMAGE')
+        initrd_image = get_bitbake_var(bb_output, 'INITRD_DEPLOY_FILE')
 
         if not initrd_image:
             initrd_image = '/dev/null'
-- 
2.34.1