This patch makes xl create check whether qemu-dm has started
correctly, and causes it to fail immediately with appropriate errors
if not. There are other bugfixes too.
More specifically:
* libxl_create_device_model forks twice rather than once so that the
process which calls libxl does not end up being the actual parent
of qemu. That avoids the need for the qemu-dm process to be reaped
at some indefinite time in the future.
* The first fork generates an intermediate process which is
responsible for writing the qemu-dm pid to xenstore and then merely
waits to collect and report on qemu-dm's exit status during
startup. New arguments to libxl_create_device_model allow the
preservation of its pid so that a later call can check whether the
startup is successful.
* The core of this functionality (the double fork, waitpid, signal
handling and so forth) is abstracted away into a new facility
libxl_spawn_... in libxl_exec.c.
Consequential changes:
* libxl_wait_for_device_model now takes a callback function parameter
which is called repeatedly in the loop iteration and allows the
caller to abort the wait.
* libxl_exec no longer calls fork; there is a new libxl_fork.
* There is a hook to override waitpid, which will be necessary for
some callers.
Remaining problems and other issues I noticed or we found:
* The error handling is rather inconsistent still and lacking in
places.
* destroy_device_model can kill random dom0 processes (!)
Signed-off-by: Ian Jackson <Ian.Jackson@eu.citrix.com>
osdeps.[hc] previously mistakenly declared and defined [v]asprintf.
These functions are available in the libc on most platforms. Also,
osdeps.h is used by xc.c but xc.c is not part of the library, so
osdeps.h is part of the public interface and should have a better
name.
So now, instead:
* osdeps.h is libxl_osdeps.h.
* _GNU_SOURCE is #defined in libxl_osdeps.h so that we get the system
[v]asprintf (and various other functions)
* libxl_osdeps.h is included first in every libxl*.c file (it needs
to be before any system headers so that _GNU_SOURCE) takes effect.
* osdeps.[hc] only provide their own reimplementation of [v]asprintf
if NEED_OWN_ASPRINTF is defined. Currently it is not ever defined
but this is provided for any platform which needs it.
* While I was editing the #includes in each .c file, I put them all
into the same order: "libxl_osdeps.h", then system headers,
then local headers.
* xs.h is included in libxl.h. This is needed for "bool"; it has to
not be typedefed in libxl.h because otherwise we get a duplicate
definition when including xs.h.
Signed-off-by: Ian Jackson <ian.jackson@eu.citrix.com>
Ian Campbell
Keir Fraser