In contrast to the CLI it is not possible to do a single pre-dump via
RPC and thus libcriu. In cr-service.c pre-dump always goes into a
pre-dump loop followed by a final dump. runc already works around this
to only do a single pre-dump by killing the CRIU process waiting for the
message for the final dump.
Trying to implement pre-dump in crun via libcriu it is not as easy to
work around CRIU's pre-dump loop expectations as with runc that directly
talks to CRIU via RPC.
We know that LXC/LXD also does single pre-dumps using the CLI and runc
also only does single pre-dumps by misusing the pre-dump loop interface.
With this commit it is possible to trigger a single pre-dump via RPC and
libcriu without misusing the interface provided via cr-service.c. So
this commit basically updates CRIU to the existing use cases.
The existing pre-dump loop still sounds like a very good idea, but so
far most tools have decided to implement the pre-dump loop themselves.
With this change we can implement pre-dump in crun to match what is
currently implemented in runc.
Signed-off-by: Adrian Reber <areber@redhat.com>
51a1adbc03