On Tue, Aug 07, 2018 at 01:31:22PM -0600, Alex Williamson wrote:
> A simple true/false internal state does not allow multiple users. Fix
> this within the existing interface by converting to a counter, so long
> as the counter is elevated, ballooning is inhibited.
>
> Reviewed-by: David Hildenbrand <david@xxxxxxxxxx>
> Reviewed-by: Peter Xu <peterx@xxxxxxxxxx>
> Reviewed-by: Cornelia Huck <cohuck@xxxxxxxxxx>
> Signed-off-by: Alex Williamson <alex.williamson@xxxxxxxxxx>
> ---
> balloon.c | 13 ++++++++++---
> 1 file changed, 10 insertions(+), 3 deletions(-)
>
> diff --git a/balloon.c b/balloon.c
> index 6bf0a9681377..931987983858 100644
> --- a/balloon.c
> +++ b/balloon.c
> @@ -26,6 +26,7 @@
>
> #include "qemu/osdep.h"
> #include "qemu-common.h"
> +#include "qemu/atomic.h"
> #include "exec/cpu-common.h"
> #include "sysemu/kvm.h"
> #include "sysemu/balloon.h"
> @@ -37,16 +38,22 @@
> static QEMUBalloonEvent *balloon_event_fn;
> static QEMUBalloonStatus *balloon_stat_fn;
> static void *balloon_opaque;
> -static bool balloon_inhibited;
> +static int balloon_inhibit_count;
>
> bool qemu_balloon_is_inhibited(void)
> {
> - return balloon_inhibited;
> + return atomic_read(&balloon_inhibit_count) > 0;
> }
>
> void qemu_balloon_inhibit(bool state)
> {
> - balloon_inhibited = state;
> + if (state) {
> + atomic_inc(&balloon_inhibit_count);
> + } else {
> + atomic_dec(&balloon_inhibit_count);
> + }
> +
> + assert(atomic_read(&balloon_inhibit_count) >= 0);
> }
>
> static bool have_balloon(Error **errp)
This blocks QEMU_MADV_WONTNEED but it also blocks QEMU_MADV_WILLNEED.
Is this necessarily a good idea?
> --
> 2.18.0
