[libvirt] [PATCH] qemu: use systemd's TerminateMachine to kill all processes

[Guido Günther]

On Tue, Sep 30, 2014 at 03:44:41PM +0100, Daniel P. Berrange wrote:
> On Tue, Sep 30, 2014 at 10:43:47AM -0400, Cole Robinson wrote:
> > On 09/30/2014 10:25 AM, Guido Günther wrote:
> > > On Tue, Sep 30, 2014 at 03:22:41PM +0100, Daniel P. Berrange wrote:
> > >> On Tue, Sep 30, 2014 at 10:10:51AM -0400, Cole Robinson wrote:
> > >>> On 09/25/2014 08:30 AM, Guido Günther wrote:
> > >>>> If we don't properly clean up all processes in the
> > >>>> machine-<vmname>.scope systemd won't remove the cgroup and subsequent vm
> > >>>> starts fail with
> > >>>>
> > >>>>   'CreateMachine: File exists'
> > >>>>
> > >>>> Additional processes can e.g. be added via
> > >>>>
> > >>>>   echo $PID > /sys/fs/cgroup/systemd/machine.slice/machine-${VMNAME}.scope/tasks
> > >>>>
> > >>>> but there are other cases like
> > >>>>
> > >>>>   http://bugs.debian.org/761521
> > >>>>
> > >>>> Invoke TerminateMachine to be on the safe side since systemd tracks the
> > >>>> cgroup anyway. This is a noop if all processes have terminated already.
> > >>>
> > >>> Thanks for the patch, I've definitely seen this a handful of times on Fedora
> > >>> as well.
> > >>>
> > >>>> ---
> > >>>>  src/libvirt_private.syms |  1 +
> > >>>>  src/qemu/qemu_cgroup.c   | 11 ++++++++++-
> > >>>>  src/qemu/qemu_cgroup.h   |  2 +-
> > >>>>  src/qemu/qemu_process.c  |  4 ++--
> > >>>>  src/util/vircgroup.c     | 11 +++++++++++
> > >>>>  src/util/vircgroup.h     |  5 +++++
> > >>>>  6 files changed, 30 insertions(+), 4 deletions(-)
> > >>>>
> > >>>> diff --git a/src/libvirt_private.syms b/src/libvirt_private.syms
> > >>>> index 51a692b..99ef1db 100644
> > >>>> --- a/src/libvirt_private.syms
> > >>>> +++ b/src/libvirt_private.syms
> > >>>> @@ -1115,6 +1115,7 @@ virCgroupSetMemorySoftLimit;
> > >>>>  virCgroupSetMemSwapHardLimit;
> > >>>>  virCgroupSetOwner;
> > >>>>  virCgroupSupportsCpuBW;
> > >>>> +virCgroupTerminateMachine;
> > >>>>  
> > >>>>  
> > >>>>  # util/virclosecallbacks.h
> > >>>> diff --git a/src/qemu/qemu_cgroup.c b/src/qemu/qemu_cgroup.c
> > >>>> index 7c6b2c1..0ab7227 100644
> > >>>> --- a/src/qemu/qemu_cgroup.c
> > >>>> +++ b/src/qemu/qemu_cgroup.c
> > >>>> @@ -1188,13 +1188,22 @@ qemuSetupCgroupForIOThreads(virDomainObjPtr vm)
> > >>>>  }
> > >>>>  
> > >>>>  int
> > >>>> -qemuRemoveCgroup(virDomainObjPtr vm)
> > >>>> +qemuRemoveCgroup(virQEMUDriverPtr driver,
> > >>>> +                 virDomainObjPtr vm)
> > >>>>  {
> > >>>>      qemuDomainObjPrivatePtr priv = vm->privateData;
> > >>>> +    virQEMUDriverConfigPtr cfg = virQEMUDriverGetConfig(driver);
> > >>>>  
> > >>>>      if (priv->cgroup == NULL)
> > >>>>          return 0; /* Not supported, so claim success */
> > >>>>  
> > >>>> +    if (virCgroupTerminateMachine(vm->def->name,
> > >>>> +                                  "qemu",
> > >>>> +                                  cfg->privileged) < 0) {
> > >>>> +        if (!virCgroupNewIgnoreError())
> > >>>> +            VIR_DEBUG("Failed to terminate cgroup for %s", vm->def->name);
> > >>>> +    }
> > >>>> +
> > >>>>      return virCgroupRemove(priv->cgroup);
> > >>>>  }
> > >>>>  
> > >>>> diff --git a/src/qemu/qemu_cgroup.h b/src/qemu/qemu_cgroup.h
> > >>>> index 8a2c723..4a4f22c 100644
> > >>>> --- a/src/qemu/qemu_cgroup.h
> > >>>> +++ b/src/qemu/qemu_cgroup.h
> > >>>> @@ -66,7 +66,7 @@ int qemuSetupCgroupForIOThreads(virDomainObjPtr vm);
> > >>>>  int qemuSetupCgroupForEmulator(virQEMUDriverPtr driver,
> > >>>>                                 virDomainObjPtr vm,
> > >>>>                                 virBitmapPtr nodemask);
> > >>>> -int qemuRemoveCgroup(virDomainObjPtr vm);
> > >>>> +int qemuRemoveCgroup(virQEMUDriverPtr driver, virDomainObjPtr vm);
> > >>>>  int qemuAddToCgroup(virDomainObjPtr vm);
> > >>>>  
> > >>>>  #endif /* __QEMU_CGROUP_H__ */
> > >>>> diff --git a/src/qemu/qemu_process.c b/src/qemu/qemu_process.c
> > >>>> index 13614e9..e7cce1a 100644
> > >>>> --- a/src/qemu/qemu_process.c
> > >>>> +++ b/src/qemu/qemu_process.c
> > >>>> @@ -4131,7 +4131,7 @@ int qemuProcessStart(virConnectPtr conn,
> > >>>>      /* Ensure no historical cgroup for this VM is lying around bogus
> > >>>>       * settings */
> > >>>>      VIR_DEBUG("Ensuring no historical cgroup is lying around");
> > >>>> -    qemuRemoveCgroup(vm);
> > >>>> +    qemuRemoveCgroup(driver, vm);
> > >>>>  
> > >>>>      for (i = 0; i < vm->def->ngraphics; ++i) {
> > >>>>          virDomainGraphicsDefPtr graphics = vm->def->graphics[i];
> > >>>> @@ -4909,7 +4909,7 @@ void qemuProcessStop(virQEMUDriverPtr driver,
> > >>>>      }
> > >>>>  
> > >>>>   retry:
> > >>>> -    if ((ret = qemuRemoveCgroup(vm)) < 0) {
> > >>>> +    if ((ret = qemuRemoveCgroup(driver, vm)) < 0) {
> > >>>>          if (ret == -EBUSY && (retries++ < 5)) {
> > >>>>              usleep(200*1000);
> > >>>>              goto retry;
> > >>>> diff --git a/src/util/vircgroup.c b/src/util/vircgroup.c
> > >>>> index 1dbe6f9..d69f71b 100644
> > >>>> --- a/src/util/vircgroup.c
> > >>>> +++ b/src/util/vircgroup.c
> > >>>> @@ -1680,6 +1680,17 @@ virCgroupNewMachineSystemd(const char *name,
> > >>>>  }
> > >>>>  
> > >>>>  
> > >>>> +/*
> > >>>> + * Returns 0 on success, -1 on fatal error
> > >>>> + */
> > >>>> +int virCgroupTerminateMachine(const char *name,
> > >>>> +                              const char *drivername,
> > >>>> +                              bool privileged)
> > >>>> +{
> > >>>> +    return virSystemdTerminateMachine(name, drivername, privileged);
> > >>>> +}
> > >>>> +
> > >>>> +
> > >>>>  static int
> > >>>>  virCgroupNewMachineManual(const char *name,
> > >>>>                            const char *drivername,
> > >>>> diff --git a/src/util/vircgroup.h b/src/util/vircgroup.h
> > >>>> index 19e82d1..7718a07 100644
> > >>>> --- a/src/util/vircgroup.h
> > >>>> +++ b/src/util/vircgroup.h
> > >>>> @@ -106,6 +106,11 @@ int virCgroupNewMachine(const char *name,
> > >>>>      ATTRIBUTE_NONNULL(1) ATTRIBUTE_NONNULL(2)
> > >>>>      ATTRIBUTE_NONNULL(4);
> > >>>>  
> > >>>> +int virCgroupTerminateMachine(const char *name,
> > >>>> +                              const char *drivername,
> > >>>> +                              bool privileged)
> > >>>> +    ATTRIBUTE_NONNULL(1) ATTRIBUTE_NONNULL(2);
> > >>>> +
> > >>>>  bool virCgroupNewIgnoreError(void);
> > >>>>  
> > >>>>  void virCgroupFree(virCgroupPtr *group);
> > >>>>
> > >>>
> > >>> All the above seems reasonable to me. ACK
> > >>
> > >> I'm surprised we see the problem with QEMU, but this matches what we
> > >> do for LXC and is recommended by systemd maintainers so fine to for
> > >> QEMU too.
> > > 
> > > Thanks to the two of you for reviewing. Should this go into 1.2.9 ?
> > 
> > I don't know why this patch would cause problems... but then again it's
> > cgroup/systemd stuff which makes me a little nervous. If it was my patch I'd
> > wait until after the release to be safe.
> 
> Yeah, I think I'd rather we waited, and put it in a stable release once
> we've had some usage in master.

O.k., I've also added it to Debian's experimental package.
Cheers,
 -- Guido