On Wed, Mar 09, 2011 at 05:02:24PM +0100, Jiri Denemark wrote:
> On Thu, Feb 24, 2011 at 13:42:18 +0000, Daniel P. Berrange wrote:
> > The current LXC I/O controller looks for HUP to detect
> > when a guest has quit. This isn't reliable as during
> > initial bootup it is possible that 'init' will close
> > the console and let mingetty re-open it. The shutdown
> > of containers was also flakey because it only killed
> > the libvirt I/O controller and expected container
> > processes to gracefully follow.
> >
> > Change the I/O controller such that when it see HUP
> > or an I/O error, it uses kill($PID, 0) to see if the
> > process has really quit.
> >
> > Change the container shutdown sequence to use the
> > virCgroupKillPainfully function to ensure every
> > really goes away
> >
> > This change makes the use of the 'cpu', 'cpuacct'
> > and 'memory' cgroups controllers compulsory with
> > LXC
>
> The documentation in drvlxc.html says cpuacct, memory, and devices are the
> mandatory controllers and the code lxcVmStart() agrees with that so this
> commit message needs to be corrected.
Ah yes.
> > @@ -341,7 +352,8 @@ ignorable_epoll_accept_errno(int errnum)
> > static int lxcControllerMain(int monitor,
> > int client,
> > int appPty,
> > - int contPty)
> > + int contPty,
> > + pid_t container)
> > {
> > int rc = -1;
> > int epollFd;
> > @@ -447,7 +459,13 @@ static int lxcControllerMain(int monitor,
> > ++numActive;
> > }
> > } else if (epollEvent.events & EPOLLHUP) {
> > - VIR_DEBUG("EPOLLHUP from fd %d", epollEvent.data.fd);
> > + if (lxcPidGone(container))
> > + goto cleanup;
> > + curFdOff = epollEvent.data.fd == appPty ? 0 : 1;
> > + if (fdArray[curFdOff].active) {
> > + fdArray[curFdOff].active = 0;
> > + --numActive;
> > + }
> > continue;
>
> Heh, thanks for the opportunity to learn about epoll. This might be a trivial
> question but... what if we get EPOLLIN event immediately followed by EPOLLHUP
> on the same fd? Do we end up leaving the data unread until another EPOLLIN
> arrives? Although it shouldn't be a big deal since we will just read the data
> from init after the console gets reopened by mingetty.
The previous branch in this 'if' will have handled the EPOLLIN event
so we shouldn't delay data.
> ...
> > @@ -2844,7 +2811,7 @@ static virDriver lxcDriver = {
> > lxcDomainLookupByName, /* domainLookupByName */
> > lxcDomainSuspend, /* domainSuspend */
> > lxcDomainResume, /* domainResume */
> > - lxcDomainShutdown, /* domainShutdown */
> > + NULL, /* domainShutdown */
> > NULL, /* domainReboot */
> > lxcDomainDestroy, /* domainDestroy */
> > lxcGetOSType, /* domainGetOSType */
>
> So we lost virDomainShutdown for LXC. I guess that's because it didn't really
> work anyway, right? I wonder if there is a way to do graceful shutdown for a
> container without having a special deamon in it.
Yes & no. Thinking a little more, it depends on whats running in the
container. If doing full OS virtualization though, with a real 'init',
just sending SIGTERM isn't going to work. We likely need to actually
look inside the container and see if there's a UNIX socket somewhere
we can feed 'init' a controlled shutdown sequence. And fallback to
a plain SIGTERM if none is found.
I'll work on that as a later patch...
Daniel
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