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

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Date:   Thu, 9 Dec 2021 06:21:48 +0800
From:   kernel test robot <lkp@...el.com>
To:     xiangxia.m.yue@...il.com, netdev@...r.kernel.org
Cc:     llvm@...ts.linux.dev, kbuild-all@...ts.01.org,
        Tonghao Zhang <xiangxia.m.yue@...il.com>,
        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

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.


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