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

[Uladzimir Bely <ubely@ilbers.de>]

In the email from Thursday, 23 February 2023 06:36:00 +03 user Moessbauer, Felix wrote:
> On Wed, 2023-02-22 at 20:40 +0300, Uladzimir Bely wrote:
> > In the email from Saturday, 18 February 2023 13:30:38 +03 user Felix
> > Moessbauer wrote:
> > > 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')
> > 
> > This seems to be not enough to change the name without directory,
> > since it's later concatenated with old one (deploy_dir_image)
> 
> Why would that make a difference? The new INITRD_DEPLOY_FILE variable
> should behave exactly the same as the previous INITRD_IMAGE, when set.
> If not, then this is a bug in my patch.
> 
> > 
> > >  
> > >          if not initrd_image:
> > >              initrd_image = '/dev/null'
> > > 
> >         else:
> >             initrd_image = deploy_dir_image + '/' + initrd_image`
> > 
> > Moreover, I would say, it's not good that we should now look for
> > initrd file somewhere in DEPLOYDIR="${WORKDIR}/deploy", while
> > everyone would expect to find it
> > DEPLOY_DIR_IMAGE="${DEPLOY_DIR}/images/${MACHINE}"...
> 
> This should also not be the case. The deploy location should be exactly
> the same as before. In my local tests this also always was the case.
> I'll have a second look.
> 

I've rechecked with `bitbake -e mc:qemuarm-bullseye:isar-image-base`.

Before patchset, these lines in `do_copy_boot_files`
```
if [ -f "$initrd" ]; then
    cp -f "$initrd" '${DEPLOY_DIR_IMAGE}/${INITRD_IMAGE}'
fi
```
are converted to:
```
if [ -f "$initrd" ]; then
    cp -f "$initrd" '/build/tmp/deploy/images/qemuarm/isar-image-base-debian-bullseye-qemuarm-initrd.img'
fi
```

while with the patchset we have a new transition from
```
if [ -f "$initrd" ]; then
    cp -f "$initrd" '${DEPLOYDIR}/${INITRD_DEPLOY_FILE}'
fi
```
to
```
if [ -f "$initrd" ]; then
    cp -f "$initrd" '/build/tmp/work/debian-bullseye-armhf/isar-image-base-qemuarm/1.0-r0/deploy/isar-image-base-debian-bullseye-qemuarm-initrd.img'
fi
```

So, the issue caused not by ${INITRD_DEPLOY_FILE}, but by ${DEPLOYDIR}

> With all these changes to the testsuite I have to admit that I simply
> did not run it. I lost track on how to use it after the changes.
> 

Yes, there have been many changes in testsuite recently (and more are upcoming), but related part in `start_vm.py / format_qemu_cmdline` is "stable" for years.

> I will have a second look at the patch series.
> 
> Felix
> 
> > 
> > 
> > 
> > 
> 
>