netdev - Re: [net-next v2 2/2] net: sched: support hash/classid selecting tx queue

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Message-ID: <CAMDZJNUBhpu6KLAL08+BKRCJg0JDHNCQAXtNXzcOZwTHzRgChg@mail.gmail.com>
Date:   Thu, 9 Dec 2021 09:51:17 +0800
From:   Tonghao Zhang <xiangxia.m.yue@...il.com>
To:     kernel test robot <lkp@...el.com>
Cc:     Linux Kernel Network Developers <netdev@...r.kernel.org>,
        llvm@...ts.linux.dev, kbuild-all@...ts.01.org,
        Jamal Hadi Salim <jhs@...atatu.com>,
        Cong Wang <xiyou.wangcong@...il.com>,
        Jiri Pirko <jiri@...nulli.us>,
        Jakub Kicinski <kuba@...nel.org>,
        Jonathan Lemon <jonathan.lemon@...il.com>,
        Eric Dumazet <edumazet@...gle.com>,
        Alexander Lobakin <alobakin@...me>,
        Paolo Abeni <pabeni@...hat.com>
Subject: Re: [net-next v2 2/2] net: sched: support hash/classid selecting tx queue

On Thu, Dec 9, 2021 at 6:22 AM kernel test robot <lkp@...el.com> wrote:
>
> Hi,
>
> Thank you for the patch! Perhaps something to improve:
>
> [auto build test WARNING on net-next/master]
>
> url:    https://github.com/0day-ci/linux/commits/xiangxia-m-yue-gmail-com/net-sched-allow-user-to-select-txqueue/20211208-223656
> base:   https://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next.git 1fe5b01262844be03de98afdd56d1d393df04d7e
> config: i386-randconfig-r023-20211207 (https://download.01.org/0day-ci/archive/20211209/202112090603.PxlqXFRw-lkp@intel.com/config)
> compiler: clang version 14.0.0 (https://github.com/llvm/llvm-project 097a1cb1d5ebb3a0ec4bcaed8ba3ff6a8e33c00a)
> reproduce (this is a W=1 build):
>         wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
>         chmod +x ~/bin/make.cross
>         # https://github.com/0day-ci/linux/commit/522fbcfdde012bc46d29aa216bdfa73f512adcbd
>         git remote add linux-review https://github.com/0day-ci/linux
>         git fetch --no-tags linux-review xiangxia-m-yue-gmail-com/net-sched-allow-user-to-select-txqueue/20211208-223656
>         git checkout 522fbcfdde012bc46d29aa216bdfa73f512adcbd
>         # save the config file to linux build tree
>         mkdir build_dir
>         COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 O=build_dir ARCH=i386 SHELL=/bin/bash mm/ net/sched/
>
> If you fix the issue, kindly add following tag as appropriate
> Reported-by: kernel test robot <lkp@...el.com>
>
> All warnings (new ones prefixed by >>):
>
> >> net/sched/act_skbedit.c:39:11: warning: variable 'hash' is used uninitialized whenever 'if' condition is false [-Wsometimes-uninitialized]
>            else if (params->flags & SKBEDIT_F_QUEUE_MAPPING_HASH)
>                     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>    net/sched/act_skbedit.c:42:34: note: uninitialized use occurs here
>            queue_mapping = queue_mapping + hash % mapping_mod;
>                                            ^~~~
>    net/sched/act_skbedit.c:39:7: note: remove the 'if' if its condition is always true
>            else if (params->flags & SKBEDIT_F_QUEUE_MAPPING_HASH)
>                 ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>    net/sched/act_skbedit.c:32:10: note: initialize the variable 'hash' to silence this warning
>            u32 hash;
>                    ^
>                     = 0
>    1 warning generated.
v1 has set the hash = 0, in v2, I remove it, because the hash will be
set by classid or skb-hash.
In next version, I will fix that warning.
>
> vim +39 net/sched/act_skbedit.c
>
>     26
>     27  static u16 tcf_skbedit_hash(struct tcf_skbedit_params *params,
>     28                              struct sk_buff *skb)
>     29  {
>     30          u16 queue_mapping = params->queue_mapping;
>     31          u16 mapping_mod = params->mapping_mod;
>     32          u32 hash;
>     33
>     34          if (!(params->flags & SKBEDIT_F_QUEUE_MAPPING_HASH_MASK))
>     35                  return netdev_cap_txqueue(skb->dev, queue_mapping);
>     36
>     37          if (params->flags & SKBEDIT_F_QUEUE_MAPPING_CLASSID)
>     38                  hash = jhash_1word(task_get_classid(skb), 0);
>   > 39          else if (params->flags & SKBEDIT_F_QUEUE_MAPPING_HASH)
>     40                  hash = skb_get_hash(skb);
>     41
>     42          queue_mapping = queue_mapping + hash % mapping_mod;
>     43          return netdev_cap_txqueue(skb->dev, queue_mapping);
>     44  }
>     45
>
> ---
> 0-DAY CI Kernel Test Service, Intel Corporation
> https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org



-- 
Best regards, Tonghao