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



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 ?
Cheers,
 -- Guido


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