Re: [qemu-s390x] [Qemu-devel] [PULL 1/4] balloon: Allow multiple inhibit users

[Christian Borntraeger]

This breaks qemu-io test for me.

#0  0x000003ff98f3e2d4 in raise () at /lib64/libc.so.6
#1  0x000003ff98f239a8 in abort () at /lib64/libc.so.6
#2  0x000003ff98f3632e in __assert_fail_base () at /lib64/libc.so.6
#3  0x000003ff98f363ac in  () at /lib64/libc.so.6
#4  0x000000000108301a in qemu_balloon_inhibit (address@hidden) at 
/home/cborntra/REPOS/qemu/balloon.c:56
#5  0x00000000012026f2 in postcopy_ram_incoming_cleanup (address@hidden) at 
/home/cborntra/REPOS/qemu/migration/postcopy-ram.c:542
#6  0x00000000011eed5e in process_incoming_migration_co (opaque=<optimized 
out>) at /home/cborntra/REPOS/qemu/migration/migration.c:407
#7  0x0000000001374000 in coroutine_trampoline (i0=<optimized out>, 
i1=<optimized out>) at /home/cborntra/REPOS/qemu/util/coroutine-ucontext.c:116
#8  0x000003ff98f53c02 in __makecontext_ret () at /lib64/libc.so.6

Cant see right now whats wrong.

On 08/17/2018 07:08 PM, 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 <address@hidden>
> Reviewed-by: Peter Xu <address@hidden>
> Reviewed-by: Cornelia Huck <address@hidden>
> Signed-off-by: Alex Williamson <address@hidden>
> ---
>  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)
> 
>