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

[Slava Ovsiienko <viacheslavo@nvidia.com>]

Hi, Ferruh

> -----Original Message-----
> From: Ferruh Yigit <ferruh.yigit@intel.com>
> Sent: Wednesday, November 10, 2021 18:57
> To: Chengfeng Ye <cyeaa@connect.ust.hk>; david.marchand@redhat.com;
> Slava Ovsiienko <viacheslavo@nvidia.com>; Shahaf Shuler
> <shahafs@nvidia.com>; Matan Azrad <matan@nvidia.com>
> Cc: dev@dpdk.org; stable@dpdk.org
> Subject: Re: [dpdk-dev] [PATCH v5] net/mlx5: fix mutex unlock in txpp
> cleanup
> 
> 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: stable@dpdk.org
> >
> > Signed-off-by: Chengfeng Ye <cyeaa@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?
mmm, It seems "claim_zero()" macro would be better here:

claim_zero(pthread_mutex_lock(&sh->txpp.mutex));

I will provide the cleanup patch, thank you for noticing that

> 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
It would directly replace MLX5_ASSERT(exp) with RTE_SET_USED(exp)
if there is neither RTE_ENABLE_ASSERT nor RTE_LIBRTE_MLX5_DEBUG.
We would not like to drop the "not used" check functionality at all , right?

With best regards,
Slava