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



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

- Cole


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