[systemd-devel] [RFC] [PATCH 0/3] resume: implement support for resuming from hibernation
Umut Tezduyar Lindskog
umut at tezduyar.com
Wed Aug 27 01:19:08 PDT 2014
I was wondering if a ./configure switch makes sense to disable it.
Embedded devices won't be using it.
On Sat, Aug 23, 2014 at 2:47 PM, Ivan Shapovalov <intelfx100 at gmail.com> wrote:
> This patchset allows systemd to parse resume= kernel command line parameter
> and initiate resume from the specified device.
> It adds:
> - a 'systemd-resume' tool which takes path to a device node and
> writes its major:minor to /sys/power/state;
> - a corresponding 'systemd-resume at .service' templated unit;
> - a 'systemd-resume-generator' generator which parses the kernel command line
> and instantiates the unit as necessary.
> This functionality already exists in-kernel, but only for "/dev/sdXY"-style
> pathes. Implementing it in userspace allows to use arbitrary udev-created
> symlinks, e. g. persistent block device pathes ("/dev/disk/by-foo/bar").
> Userspace parsing of resume= kernel command line parameter has been
> traditionally done in initramfs via shell scripts (for Arch Linux, this is
> "resume" mkinitcpio hook), so I feel that this feature has its place within
> Due to the nature of hibernation, the resume unit must be activated before
> any modifications to filesystems take place. This can happen
> 1) in initramfs before mounting anything, and
> 2) without initramfs before remounting rootfs read-write (provided that it is
> mounted RO initially).
> So, first patch orders all non-root fsck after local-fs-pre.target, which in
> turn allows to order the resume unit before those fsck instances.
> Second and third patches add the tool, the unit and the generator.
> There are some issues with this implementation:
> - legacy usr.mount is not automatically ordered after local-fs-pre.target,
> so systemd-resume at .service has to be manually ordered before it;
> - systemd-udevd.service, which is needed for creating persistent block device
> symlinks, is transitively ordered after systemd-remount-fs.service via at
> least systemd-udev-hwdb-update.service and systemd-sysusers.service.
> Hence, if these units are present (at least initramfs-less case), an ordering
> cycle happens and resume is impossible.
> So, I would like someone to comment on these.
> This is my first patch to this project, so feel free to flak me for missing
> something obvious :)
> Thanks for reviewing!
> Ivan Shapovalov (3):
> units: order systemd-fsck at .service after local-fs-pre.target.
> resume: add a tool to write a device node's major:minor to /sys/power/resume.
> resume-generator: add a generator for instantiating the resume unit.
> Makefile-man.am | 9 ++++
> Makefile.am | 28 ++++++++--
> man/kernel-command-line.xml | 13 ++++-
> man/systemd-resume-generator.xml | 91 +++++++++++++++++++++++++++++++++
> man/systemd-resume at .service.xml | 81 +++++++++++++++++++++++++++++
> src/resume-generator/Makefile | 1 +
> src/resume-generator/resume-generator.c | 89 ++++++++++++++++++++++++++++++++
> src/resume/Makefile | 1 +
> src/resume/resume.c | 82 +++++++++++++++++++++++++++++
> units/systemd-fsck at .service.in | 2 +-
> units/systemd-resume at .service.in | 23 +++++++++
> 11 files changed, 414 insertions(+), 6 deletions(-)
> create mode 100644 man/systemd-resume-generator.xml
> create mode 100644 man/systemd-resume at .service.xml
> create mode 120000 src/resume-generator/Makefile
> create mode 100644 src/resume-generator/resume-generator.c
> create mode 120000 src/resume/Makefile
> create mode 100644 src/resume/resume.c
> create mode 100644 units/systemd-resume at .service.in
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