Re: [Xen-devel] [PATCH] tools/libs: Make xenforeignmemory_unmap_resource() idempotent

[Paul Durrant <Paul.Durrant@xxxxxxxxxx>]

> -----Original Message-----
> From: Andrew Cooper [mailto:andrew.cooper3@xxxxxxxxxx]
> Sent: 23 November 2018 15:12
> To: Xen-devel <xen-devel@xxxxxxxxxxxxx>
> Cc: Andrew Cooper <Andrew.Cooper3@xxxxxxxxxx>; Ian Jackson
> <Ian.Jackson@xxxxxxxxxx>; Wei Liu <wei.liu2@xxxxxxxxxx>; Paul Durrant
> <Paul.Durrant@xxxxxxxxxx>
> Subject: [PATCH] tools/libs: Make xenforeignmemory_unmap_resource()
> idempotent
> 
> Most other close/unmap functions are.
> 
> Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
> ---
> CC: Ian Jackson <Ian.Jackson@xxxxxxxxxx>
> CC: Wei Liu <wei.liu2@xxxxxxxxxx>
> CC: Paul Durrant <paul.durrant@xxxxxxxxxx>
> 
> This ideally wants backporting to 4.11 to hit 4.11.1
> 
> I got an unexpected shock while trying to diagnose why GVT-g is still
> broken (differently!) on staging.
> ---
>  tools/libs/foreignmemory/core.c | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/tools/libs/foreignmemory/core.c
> b/tools/libs/foreignmemory/core.c
> index 63f12e2..2516fd4 100644
> --- a/tools/libs/foreignmemory/core.c
> +++ b/tools/libs/foreignmemory/core.c
> @@ -182,7 +182,12 @@ xenforeignmemory_resource_handle
> *xenforeignmemory_map_resource(
>  int xenforeignmemory_unmap_resource(
>      xenforeignmemory_handle *fmem, xenforeignmemory_resource_handle
> *fres)
>  {
> -    int rc = osdep_xenforeignmemory_unmap_resource(fmem, fres);
> +    int rc;
> +
> +    if ( !fres )
> +        return 0;
> +
> +    rc = osdep_xenforeignmemory_unmap_resource(fmem, fres);

Freeing NULL should not be problem as this defined to do nothing so there is 
nothing about this function which is not idempotent. I assume, without looking 
yet, that it is the osdep function which needs fixing.

  Paul

> 
>      free(fres);
>      return rc;
> --
> 2.1.4


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