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.

Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
---
 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)

On 31.07.2018 01:13, 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.
> 

Not sure if "nested" is really the right term here. It is really
multiple users. anyhow

Reviewed-by: David Hildenbrand <david@redhat.com>

> Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
> ---
>  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)
> 


-- 

Thanks,

David / dhildenb

On Mon, Jul 30, 2018 at 05:13:46PM -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.
> 
> Signed-off-by: Alex Williamson <alex.williamson@redhat.com>

Reviewed-by: Peter Xu <peterx@redhat.com>

Regards,

-- 
Peter Xu

On Mon, 30 Jul 2018 17:13:46 -0600
Alex Williamson <alex.williamson@redhat.com> 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.
> 
> Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
> ---
>  balloon.c |   13 ++++++++++---
>  1 file changed, 10 insertions(+), 3 deletions(-)

Reviewed-by: Cornelia Huck <cohuck@redhat.com>