Re: [Qemu-devel] [PATCH 1/3] rcu: do not let RCU callbacks pile up indefinitely

[Fam Zheng <famz@redhat.com>]

On Wed, 02/11 18:14, Paolo Bonzini wrote:
> Always process them within half a second.  Even though waiting a little
> is useful, it is not okay to delay e.g. qemu_opts_del forever.
> 
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
> ---
>  util/rcu.c | 14 ++++++++------
>  1 file changed, 8 insertions(+), 6 deletions(-)
> 
> diff --git a/util/rcu.c b/util/rcu.c
> index c9c3e6e..486d7b6 100644
> --- a/util/rcu.c
> +++ b/util/rcu.c
> @@ -223,14 +223,16 @@ static void *call_rcu_thread(void *opaque)
>           * Fetch rcu_call_count now, we only must process elements that were
>           * added before synchronize_rcu() starts.
>           */
> -        while (n < RCU_CALL_MIN_SIZE && ++tries <= 5) {
> -            g_usleep(100000);
> -            qemu_event_reset(&rcu_call_ready_event);
> -            n = atomic_read(&rcu_call_count);
> -            if (n < RCU_CALL_MIN_SIZE) {
> -                qemu_event_wait(&rcu_call_ready_event);
> +        while (n == 0 || (n < RCU_CALL_MIN_SIZE && ++tries <= 5)) {
> +            g_usleep(10000);
> +            if (n == 0) {
> +                qemu_event_reset(&rcu_call_ready_event);
>                  n = atomic_read(&rcu_call_count);
> +                if (n == 0) {
> +                    qemu_event_wait(&rcu_call_ready_event);
> +                }
>              }
> +            n = atomic_read(&rcu_call_count);
>          }
>  
>          atomic_sub(&rcu_call_count, n);

Reviewed-by: Fam Zheng <famz@redhat.com>