Re: [dpdk-dev] [dpdk-stable] [PATCH v4 3/3] eal: fix a wrong returned value when callback exists

[David Marchand <david.marchand@redhat.com>]

On Fri, Jul 3, 2020 at 11:47 AM wangyunjian <wangyunjian@huawei.com> wrote:
>
> From: Yunjian Wang <wangyunjian@huawei.com>
>
> We should return an error value, when the callback is already exist.
>
> Fixes: a753e53d517b ("eal: add device event monitor framework")
> Cc: stable@dpdk.org
>
> Signed-off-by: Yunjian Wang <wangyunjian@huawei.com>
> ---
>  lib/librte_eal/common/eal_common_dev.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/lib/librte_eal/common/eal_common_dev.c b/lib/librte_eal/common/eal_common_dev.c
> index d990bfd..2a097aa 100644
> --- a/lib/librte_eal/common/eal_common_dev.c
> +++ b/lib/librte_eal/common/eal_common_dev.c
> @@ -431,7 +431,7 @@ static int cmp_dev_name(const struct rte_device *dev, const void *_name)
>                                 void *cb_arg)
>  {
>         struct dev_event_callback *event_cb;
> -       int ret;
> +       int ret = 0;
>
>         if (!cb_fn)
>                 return -EINVAL;
> @@ -484,7 +484,7 @@ static int cmp_dev_name(const struct rte_device *dev, const void *_name)
>         }
>
>         rte_spinlock_unlock(&dev_event_lock);
> -       return 0;
> +       return ret;
>  error:
>         free(event_cb);
>         rte_spinlock_unlock(&dev_event_lock);
> --
> 1.8.3.1

A simpler fix is to directly jump to the error label.
This has the advantage of having all errors go through a single cleanup code:

diff --git a/lib/librte_eal/common/eal_common_dev.c
b/lib/librte_eal/common/eal_common_dev.c
index 9e4f09d83e..fa47074b0b 100644
--- a/lib/librte_eal/common/eal_common_dev.c
+++ b/lib/librte_eal/common/eal_common_dev.c
@@ -480,7 +480,9 @@ rte_dev_event_callback_register(const char *device_name,
                RTE_LOG(ERR, EAL,
                        "The callback is already exist, no need "
                        "to register again.\n");
+               event_cb = NULL;
                ret = -EEXIST;
+               goto error;
        }

        rte_spinlock_unlock(&dev_event_lock);

What do you think?


-- 
David Marchand