Re: [dpdk-dev] [PATCH v5] net/mlx5: fix mutex unlock in txpp cleanup

[Ferruh Yigit]

On 10/12/2021 11:02 AM, Chengfeng Ye wrote:

The lock sh->txpp.mutex was not correctly released on one path
of cleanup function return, potentially causing the deadlock.

Fixes: d133f4cdb7 ("net/mlx5: create clock queue for packet pacing")
Cc: sta...@dpdk.org

Signed-off-by: Chengfeng Ye <cy...@connect.ust.hk>
---
  drivers/net/mlx5/mlx5_txpp.c | 6 +++++-
  1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/net/mlx5/mlx5_txpp.c b/drivers/net/mlx5/mlx5_txpp.c
index 4f6da9f2d1..0ece788a84 100644
--- a/drivers/net/mlx5/mlx5_txpp.c
+++ b/drivers/net/mlx5/mlx5_txpp.c
@@ -961,8 +961,12 @@ mlx5_txpp_stop(struct rte_eth_dev *dev)
        MLX5_ASSERT(!ret);
        RTE_SET_USED(ret);
        MLX5_ASSERT(sh->txpp.refcnt);
-       if (!sh->txpp.refcnt || --sh->txpp.refcnt)
+       if (!sh->txpp.refcnt || --sh->txpp.refcnt) {
+               ret = pthread_mutex_unlock(&sh->txpp.mutex);
+               MLX5_ASSERT(!ret);
+               RTE_SET_USED(ret);

Is this 'RTE_SET_USED()' need to be used multiple times for same variable?

This usage looks ugly, I can see why it is used but I wonder if this can
be solved differently, what about something like following:

 #ifdef RTE_LIBRTE_MLX5_DEBUG
  #define MLX5_ASSERT(exp) RTE_VERIFY(exp)
 #else
  #ifdef RTE_ENABLE_ASSERT
   #define MLX5_ASSERT(exp) RTE_ASSERT(exp)
  #else
   #define MLX5_ASSERT(exp) RTE_SET_USED(exp)
  #endif
 #endif

                return;
+       }
        /* No references any more, do actual destroy. */
        mlx5_txpp_destroy(sh);
        ret = pthread_mutex_unlock(&sh->txpp.mutex);