>>> On 21.06.17 at 11:38, <jbeul...@suse.com> wrote:
> Holding any lock while accessing the maptrack entry fields is
> pointless, as these entries are protected by their associated active
> entry lock (which is being acquired later, before re-validating the
> fields read without holding the lock).
>
> Signed-off-by: Jan Beulich <jbeul...@suse.com>
>
> --- a/xen/common/grant_table.c
> +++ b/xen/common/grant_table.c
> @@ -1122,19 +1122,14 @@ __gnttab_unmap_common(
> smp_rmb();
> map = &maptrack_entry(lgt, op->handle);
>
> - grant_read_lock(lgt);
> -
> if ( unlikely(!read_atomic(&map->flags)) )
> {
> - grant_read_unlock(lgt);
> gdprintk(XENLOG_INFO, "Zero flags for handle %#x\n", op->handle);
> op->status = GNTST_bad_handle;
> return;
> }
>
> dom = map->domid;
> - grant_read_unlock(lgt);
> -
> if ( unlikely((rd = rcu_lock_domain_by_id(dom)) == NULL) )
> {
> /* This can happen when a grant is implicitly unmapped. */
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