On Thu, Oct 09, 2014 at 09:58:30AM +0200, Martin Kletzander wrote:
> When daemon is killed right in the middle of probing a qemu binary for
> its capabilities, the VM is left running. Next time the daemon is
> starting, it cannot start qemu process because the one that's already
> running does have the pidfile flock()'d.
I was wondering if there's anything we can easily change in the way
we launch the QEMU binary so that it automatically dies when libvirtd
exits, rather than us needing to manually kill it.
The comments say we have to use daemonize to synchronize with the
monitor socket creation and I recall we've tried other approaches
to that before which failed.
Another idea would be to play with adding '-serial stdio' and then
when libvirt died stdio would get a broken pipe but I don't think
it is safe to use -serial when we have -M none so that's out.
So I guss we don't have much choice but to manually kill.
> Reported-by: Wang Yufei <james.wangyufei@xxxxxxxxxx>
>
> Signed-off-by: Martin Kletzander <mkletzan@xxxxxxxxxx>
> ---
> src/qemu/qemu_capabilities.c | 41 +++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 41 insertions(+)
>
> diff --git a/src/qemu/qemu_capabilities.c b/src/qemu/qemu_capabilities.c
> index 6fcb5c7..919780e 100644
> --- a/src/qemu/qemu_capabilities.c
> +++ b/src/qemu/qemu_capabilities.c
> @@ -3243,6 +3243,47 @@ virQEMUCapsInitQMP(virQEMUCapsPtr qemuCaps,
> config.data.nix.path = monpath;
> config.data.nix.listen = false;
>
> + /*
> + * Check if there wasn't some older qemu left running, e.g. if
> + * someone killed libvirtd during the probing phase.
> + */
> + if (virFileExists(pidfile) &&
> + virPidFileReadPath(pidfile, &pid) == 0) {
> + char *cmdpath = NULL;
> + char *cmdline = NULL;
> + int len, pos = 0;
> +
> + VIR_DEBUG("Checking if there's an older qemu process left running that "
> + "was used for capability probing");
> +
> + if (virAsprintf(&cmdpath, "/proc/%u/cmdline", pid) < 0)
> + goto cleanup;
> +
> + len = virFileReadAll(cmdpath, 1024, &cmdline);
> + VIR_FREE(cmdpath);
> +
> + /*
> + * This cycle gets trivially skipped if there was an error in
> + * virFileReadAll().
> + */
> + while (len > pos) {
> + /*
> + * Find the '-pidfile /path/to/capabilities.pidfile' to be
> + * sure we won't kill anyone else.
> + */
> + if (STREQ_NULLABLE(cmdline + pos, "-pidfile") &&
> + (pos += strlen(cmdline + pos) + 1) < len &&
> + STREQ_NULLABLE(cmdline + pos, pidfile)) {
Heh fun hack. Did you consider simply trying to connect to the monitor
socket to see if the QEMU was still there ? That would be slightly more
portable as it wouldn't rely on Linux /proc
> + virProcessKillPainfully(pid, true);
> + break;
> + }
> +
> + pos += strlen(cmdline + pos) + 1;
> + }
> +
> + VIR_FREE(cmdline);
> + }
> +
> VIR_DEBUG("Try to get caps via QMP qemuCaps=%p", qemuCaps);
Regards,
Daniel
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