Re: [Qemu-devel] [PATCH for-2.8] qtail: clean up direct access to tqe_prev field

[Paolo Bonzini <pbonzini@redhat.com>]

On 25/07/2016 14:47, Igor Mammedov wrote:
> instead of accessing tqe_prev field dircetly outside
> of queue.h use macros to check if element is in list
> and make sure that afer element is removed from list
> tqe_prev field could be used to do the same check.
> 
> Signed-off-by: Igor Mammedov <imammedo@redhat.com>
> ---
> The patch is split from as cleanup is not urgent
>   [PATCH 0/6] Fix migration issues with arbitrary cpu-hot(un)plug
> and made on top of
>   [PATCH v2 0/6] Fix migration issues with arbitrary cpu-hot(un)plug
> 
> posting it to list so that it won't be forgotten or lost
> and affected people could review it at there leisure time.
> 
> ---
>  include/qemu/queue.h | 2 ++
>  blockdev.c           | 2 +-
>  exec.c               | 3 +--
>  net/filter.c         | 2 +-
>  4 files changed, 5 insertions(+), 4 deletions(-)
> 
> diff --git a/include/qemu/queue.h b/include/qemu/queue.h
> index c2b6c81..342073f 100644
> --- a/include/qemu/queue.h
> +++ b/include/qemu/queue.h
> @@ -407,6 +407,7 @@ struct {                                                                \
>          else                                                            \
>                  (head)->tqh_last = (elm)->field.tqe_prev;               \
>          *(elm)->field.tqe_prev = (elm)->field.tqe_next;                 \
> +        (elm)->field.tqe_prev = NULL;                                   \
>  } while (/*CONSTCOND*/0)
>  
>  #define QTAILQ_FOREACH(var, head, field)                                \
> @@ -430,6 +431,7 @@ struct {                                                                \
>  #define QTAILQ_EMPTY(head)               ((head)->tqh_first == NULL)
>  #define QTAILQ_FIRST(head)               ((head)->tqh_first)
>  #define QTAILQ_NEXT(elm, field)          ((elm)->field.tqe_next)
> +#define QTAILQ_IN_USE(elm, field)        ((elm)->field.tqe_prev != NULL)
>  
>  #define QTAILQ_LAST(head, headname) \
>          (*(((struct headname *)((head)->tqh_last))->tqh_last))
> diff --git a/blockdev.c b/blockdev.c
> index eafeba9..0b73158 100644
> --- a/blockdev.c
> +++ b/blockdev.c
> @@ -4031,7 +4031,7 @@ void qmp_x_blockdev_del(bool has_id, const char *id,
>              goto out;
>          }
>  
> -        if (!blk && !bs->monitor_list.tqe_prev) {
> +        if (!blk && !QTAILQ_IN_USE(bs, monitor_list)) {
>              error_setg(errp, "Node %s is not owned by the monitor",
>                         bs->node_name);
>              goto out;
> diff --git a/exec.c b/exec.c
> index 50e3ee2..8e8416b 100644
> --- a/exec.c
> +++ b/exec.c
> @@ -614,14 +614,13 @@ void cpu_exec_exit(CPUState *cpu)
>      CPUClass *cc = CPU_GET_CLASS(cpu);
>  
>      cpu_list_lock();
> -    if (cpu->node.tqe_prev == NULL) {
> +    if (!QTAILQ_IN_USE(cpu, node)) {
>          /* there is nothing to undo since cpu_exec_init() hasn't been called */
>          cpu_list_unlock();
>          return;
>      }
>  
>      QTAILQ_REMOVE(&cpus, cpu, node);
> -    cpu->node.tqe_prev = NULL;
>      cpu->cpu_index = UNASSIGNED_CPU_INDEX;
>      cpu_list_unlock();
>  
> diff --git a/net/filter.c b/net/filter.c
> index 888fe6d..1dfd2ca 100644
> --- a/net/filter.c
> +++ b/net/filter.c
> @@ -239,7 +239,7 @@ static void netfilter_finalize(Object *obj)
>      }
>  
>      if (nf->netdev && !QTAILQ_EMPTY(&nf->netdev->filters) &&
> -        nf->next.tqe_prev) {
> +        QTAILQ_IN_USE(nf, next)) {
>          QTAILQ_REMOVE(&nf->netdev->filters, nf, next);
>      }
>      g_free(nf->netdev_id);
> 

Looks good, thanks!

Paolo