[PATCH] libxl: libxl_internal.h: Clarify ao rule against internal callers

[PATCH] libxl: libxl_internal.h: Clarify ao rule against internal callers

[Ian Jackson]

Signed-off-by: Ian Jackson <Ian.Jackson@eu.citrix.com>
CC: Ian Campbell <ian.campbell@citrix.com>
CC: Wei Liu <wei.liu2@citrix.com>
CC: Juergen Gross <jgross@suse.com>
---
 tools/libxl/libxl_internal.h |    5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/tools/libxl/libxl_internal.h b/tools/libxl/libxl_internal.h
index 465aaaa..bfc0729 100644
--- a/tools/libxl/libxl_internal.h
+++ b/tools/libxl/libxl_internal.h
@@ -1911,8 +1911,9 @@ _hidden void libxl__egc_cleanup(libxl__egc *egc);
  * All "slow" functions (see below for the exact definition) need to
  * use the asynchronous operation ("ao") machinery.  The function
  * should take a parameter const libxl_asyncop_how *ao_how and must
- * start with a call to AO_INITIATOR_ENTRY.  These functions MAY NOT
- * be called from inside libxl, because they can cause reentrancy
+ * start with a call to AO_CREATE or equivalent.  These functions MAY
+ * NOT be called from inside libxl (regardless of what is passed for
+ * ao_how), because they can cause reentrancy hazards due to
  * callbacks.
  *
  * For the same reason functions taking an ao_how may make themselves
-- 
1.7.10.4

Re: [PATCH] libxl: libxl_internal.h: Clarify ao rule against internal callers

[Juergen Gross]

On 06/11/2015 06:57 PM, Ian Jackson wrote:
> Signed-off-by: Ian Jackson <Ian.Jackson@eu.citrix.com>
> CC: Ian Campbell <ian.campbell@citrix.com>
> CC: Wei Liu <wei.liu2@citrix.com>
> CC: Juergen Gross <jgross@suse.com>
> ---
>   tools/libxl/libxl_internal.h |    5 +++--
>   1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/tools/libxl/libxl_internal.h b/tools/libxl/libxl_internal.h
> index 465aaaa..bfc0729 100644
> --- a/tools/libxl/libxl_internal.h
> +++ b/tools/libxl/libxl_internal.h
> @@ -1911,8 +1911,9 @@ _hidden void libxl__egc_cleanup(libxl__egc *egc);
>    * All "slow" functions (see below for the exact definition) need to
>    * use the asynchronous operation ("ao") machinery.  The function
>    * should take a parameter const libxl_asyncop_how *ao_how and must
> - * start with a call to AO_INITIATOR_ENTRY.  These functions MAY NOT
> - * be called from inside libxl, because they can cause reentrancy
> + * start with a call to AO_CREATE or equivalent.  These functions MAY
> + * NOT be called from inside libxl (regardless of what is passed for
> + * ao_how), because they can cause reentrancy hazards due to
>    * callbacks.
>    *
>    * For the same reason functions taking an ao_how may make themselves
>

Now it's 100% clear what to avoid.

Acked-by: Juergen Gross <jgross@suse.com>

Re: [PATCH] libxl: libxl_internal.h: Clarify ao rule against internal callers

[Ian Jackson]

Juergen Gross writes ("Re: [Xen-devel] [PATCH] libxl: libxl_internal.h: Clarify ao rule against internal callers"):
> Now it's 100% clear what to avoid.
> 
> Acked-by: Juergen Gross <jgross@suse.com>

Thanks, pushed.

Ian.

Re: [PATCH] libxl: libxl_internal.h: Clarify ao rule against internal callers

[Ian Campbell]

On Thu, 2015-06-11 at 17:57 +0100, Ian Jackson wrote:
> Signed-off-by: Ian Jackson <Ian.Jackson@eu.citrix.com>
> CC: Ian Campbell <ian.campbell@citrix.com>
> CC: Wei Liu <wei.liu2@citrix.com>
> CC: Juergen Gross <jgross@suse.com>

Acked-by: Ian Campbell <ian.campbell@citrix.com>

AO_INITIATOR_ENTRY was just a stray remainder of some wip name?

> ---
>  tools/libxl/libxl_internal.h |    5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/tools/libxl/libxl_internal.h b/tools/libxl/libxl_internal.h
> index 465aaaa..bfc0729 100644
> --- a/tools/libxl/libxl_internal.h
> +++ b/tools/libxl/libxl_internal.h
> @@ -1911,8 +1911,9 @@ _hidden void libxl__egc_cleanup(libxl__egc *egc);
>   * All "slow" functions (see below for the exact definition) need to
>   * use the asynchronous operation ("ao") machinery.  The function
>   * should take a parameter const libxl_asyncop_how *ao_how and must
> - * start with a call to AO_INITIATOR_ENTRY.  These functions MAY NOT
> - * be called from inside libxl, because they can cause reentrancy
> + * start with a call to AO_CREATE or equivalent.  These functions MAY
> + * NOT be called from inside libxl (regardless of what is passed for
> + * ao_how), because they can cause reentrancy hazards due to
>   * callbacks.
>   *
>   * For the same reason functions taking an ao_how may make themselves

Re: [PATCH] libxl: libxl_internal.h: Clarify ao rule against internal callers

[Ian Jackson]

Ian Campbell writes ("Re: [PATCH] libxl: libxl_internal.h: Clarify ao rule against internal callers"):
> On Thu, 2015-06-11 at 17:57 +0100, Ian Jackson wrote:
> > Signed-off-by: Ian Jackson <Ian.Jackson@eu.citrix.com>
> > CC: Ian Campbell <ian.campbell@citrix.com>
> > CC: Wei Liu <wei.liu2@citrix.com>
> > CC: Juergen Gross <jgross@suse.com>
> 
> Acked-by: Ian Campbell <ian.campbell@citrix.com>
> 
> AO_INITIATOR_ENTRY was just a stray remainder of some wip name?

Yes.

Thanks,
Ian.