Re: [Qemu-devel] [PATCH v2 3/5] migration: remove unnecessary variables len in QIOChannelRDMA

["Dr. David Alan Gilbert" <dgilbert@redhat.com>]

* Lidong Chen (jemmy858585@gmail.com) wrote:
> Because qio_channel_rdma_writev and qio_channel_rdma_readv maybe invoked
> by different threads concurrently, this patch removes unnecessary variables
> len in QIOChannelRDMA and use local variable instead.
> 
> Signed-off-by: Lidong Chen <lidongchen@tencent.com>

I'm OK with this patch as is; but now you're making me worried that I
don't quite understand what thrads are accessing it at the same time; we
need to document/comment what's accessed concurrently.

Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>

> ---
>  migration/rdma.c | 15 +++++++--------
>  1 file changed, 7 insertions(+), 8 deletions(-)
> 
> diff --git a/migration/rdma.c b/migration/rdma.c
> index c745427..f5c1d02 100644
> --- a/migration/rdma.c
> +++ b/migration/rdma.c
> @@ -404,7 +404,6 @@ struct QIOChannelRDMA {
>      QIOChannel parent;
>      RDMAContext *rdma;
>      QEMUFile *file;
> -    size_t len;
>      bool blocking; /* XXX we don't actually honour this yet */
>  };
>  
> @@ -2640,6 +2639,7 @@ static ssize_t qio_channel_rdma_writev(QIOChannel *ioc,
>      int ret;
>      ssize_t done = 0;
>      size_t i;
> +    size_t len = 0;
>  
>      CHECK_ERROR_STATE();
>  
> @@ -2659,10 +2659,10 @@ static ssize_t qio_channel_rdma_writev(QIOChannel *ioc,
>          while (remaining) {
>              RDMAControlHeader head;
>  
> -            rioc->len = MIN(remaining, RDMA_SEND_INCREMENT);
> -            remaining -= rioc->len;
> +            len = MIN(remaining, RDMA_SEND_INCREMENT);
> +            remaining -= len;
>  
> -            head.len = rioc->len;
> +            head.len = len;
>              head.type = RDMA_CONTROL_QEMU_FILE;
>  
>              ret = qemu_rdma_exchange_send(rdma, &head, data, NULL, NULL, NULL);
> @@ -2672,8 +2672,8 @@ static ssize_t qio_channel_rdma_writev(QIOChannel *ioc,
>                  return ret;
>              }
>  
> -            data += rioc->len;
> -            done += rioc->len;
> +            data += len;
> +            done += len;
>          }
>      }
>  
> @@ -2768,8 +2768,7 @@ static ssize_t qio_channel_rdma_readv(QIOChannel *ioc,
>              }
>          }
>      }
> -    rioc->len = done;
> -    return rioc->len;
> +    return done;
>  }
>  
>  /*
> -- 
> 1.8.3.1
> 
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK