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Re: [libvirt] [PATCH 3/6] libxl: Fix race between destruction of objects



On Mon, Jan 21, 2013 at 12:22:21PM -0700, Jim Fehlig wrote:
> It is possible to destroy and cleanup a VM, resulting in freeing the
> libxlDomainObjPrivate object and associated libxl ctx, before all fds and
> timeouts have been deregistered and destroyed.
> 
> Fix this race by incrementing the reference count on libxlDomainObjPrivate
> for each fd and timeout registration.  Only when all fds and timeouts are
> deregistered and destroyed will the libxlDomainObjPrivate be destroyed.
> ---
>  src/libxl/libxl_driver.c | 16 +++++++++++++++-
>  1 file changed, 15 insertions(+), 1 deletion(-)
> 
> diff --git a/src/libxl/libxl_driver.c b/src/libxl/libxl_driver.c
> index 81c04ed..530a17f 100644
> --- a/src/libxl/libxl_driver.c
> +++ b/src/libxl/libxl_driver.c
> @@ -111,7 +111,11 @@ libxlDriverUnlock(libxlDriverPrivatePtr driver)
>  static void
>  libxlEventHookInfoFree(void *obj)
>  {
> -    VIR_FREE(obj);
> +    libxlEventHookInfoPtr info = obj;
> +
> +    /* Drop reference on libxlDomainObjPrivate */
> +    virObjectUnref(info->priv);
> +    VIR_FREE(info);
>  }
>  
>  static void
> @@ -161,6 +165,11 @@ libxlFDRegisterEventHook(void *priv, int fd, void **hndp,
>      }
>  
>      info->priv = priv;
> +    /* Take a reference on the domain object.  Reference is dropped in
> +       libxlEventHookInfoFree, ensuring the domain object outlives the fd
> +       event objects. */
> +    virObjectRef(info->priv);
> +
>      info->xl_priv = xl_priv;
>      *hndp = info;
>  
> @@ -255,6 +264,11 @@ libxlTimeoutRegisterEventHook(void *priv,
>      }
>  
>      info->priv = priv;
> +    /* Also take a reference on the domain object.  Reference is dropped in
> +       libxlEventHookInfoFree, ensuring the domain object outlives the timeout
> +       event objects. */
> +    virObjectRef(info->priv);
> +
>      info->xl_priv = xl_priv;
>      *hndp = info;

  Sounds good, ACK

Daniel

-- 
Daniel Veillard      | Open Source and Standards, Red Hat
veillard redhat com  | libxml Gnome XML XSLT toolkit  http://xmlsoft.org/
http://veillard.com/ | virtualization library  http://libvirt.org/


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