Re: [Xen-devel] [PATCH 02/14] libxl: Propagate errno from hypercall instead of anything else.

[Ian Campbell <ian.campbell@xxxxxxxxxx>]

On Mon, 2015-03-16 at 11:39 -0400, Konrad Rzeszutek Wilk wrote:
> After we have done the hypercall - the errno has the failure
> code. However our usage of pthread and munmap can trigger them
> to manipulate the errno with their failure values. That would
> be bad as what we care about is just the hypercall error value.
> 
> Another solution to this would be to save the 'errno' from
> pthread/munmap/madvise as an extra parameter to be analyzed
> later. However the call-sites above us do not care about it.
> 
> Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>

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

> ---
>  tools/libxc/xc_freebsd_osdep.c | 3 +++
>  tools/libxc/xc_hcall_buf.c     | 6 ++++++
>  tools/libxc/xc_linux_osdep.c   | 3 +++
>  3 files changed, 12 insertions(+)
> 
> diff --git a/tools/libxc/xc_freebsd_osdep.c b/tools/libxc/xc_freebsd_osdep.c
> index 151d3bf..bb6d240 100644
> --- a/tools/libxc/xc_freebsd_osdep.c
> +++ b/tools/libxc/xc_freebsd_osdep.c
> @@ -125,10 +125,13 @@ static void 
> freebsd_privcmd_free_hypercall_buffer(xc_interface *xch,
>                                                    int npages)
>  {
>  
> +    int saved_errno = errno;
>      /* Unlock pages */
>      munlock(ptr, npages * XC_PAGE_SIZE);
>  
>      munmap(ptr, npages * XC_PAGE_SIZE);
> +    /* We MUST propagate the hypercall errno, not unmap calls. */

If you have cause to resend then:

 /* We MUST Propagate the hypercall's ernno, not the unmap call's. */.

> +    /* Ignore the pthread errors. */

s/the //

(both throughout).

Not a big deal but if it needs resending anyway

Ian.


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