netdev - Re: [PATCH net-next 2/2] net: sched: Lockless Token Bucket (LTB) Qdisc

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Date:   Tue, 7 Jul 2020 23:42:24 +0800
From:   kernel test robot <lkp@...el.com>
To:     "YU, Xiangning" <xiangning.yu@...baba-inc.com>,
        netdev@...r.kernel.org
Cc:     kbuild-all@...ts.01.org, clang-built-linux@...glegroups.com
Subject: Re: [PATCH net-next 2/2] net: sched: Lockless Token Bucket (LTB)
 Qdisc

Hi Xiangning",

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/YU-Xiangning/Lockless-Token-Bucket-LTB-Qdisc/20200707-020918
base:   https://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next.git 5bd6ff0c6fe6c138aebe8d3bf7163420386c7ca7
config: x86_64-allyesconfig (attached as .config)
compiler: clang version 11.0.0 (https://github.com/llvm/llvm-project 02946de3802d3bc65bc9f2eb9b8d4969b5a7add8)
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
        # install x86_64 cross compiling tool for clang build
        # apt-get install binutils-x86-64-linux-gnu
        # save the attached .config to linux build tree
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross ARCH=x86_64 

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/sch_ltb.c:832:6: warning: variable 'err' is used uninitialized whenever 'if' condition is true [-Wsometimes-uninitialized]
           if (!opt)
               ^~~~
   net/sched/sch_ltb.c:882:9: note: uninitialized use occurs here
           return err;
                  ^~~
   net/sched/sch_ltb.c:832:2: note: remove the 'if' if its condition is always false
           if (!opt)
           ^~~~~~~~~
   net/sched/sch_ltb.c:830:9: note: initialize the variable 'err' to silence this warning
           int err;
                  ^
                   = 0
   1 warning generated.

vim +832 net/sched/sch_ltb.c

   817	
   818	static int ltb_change_class(struct Qdisc *sch, u32 classid,
   819				    u32 parentid, struct nlattr **tca,
   820				    unsigned long *arg, struct netlink_ext_ack *extack)
   821	{
   822		struct ltb_sched *ltb  = qdisc_priv(sch);
   823		struct ltb_class *cl = (struct ltb_class *)*arg, *parent;
   824		struct nlattr *opt = tca[TCA_OPTIONS];
   825		struct nlattr *tb[TCA_LTB_MAX + 1];
   826		struct tc_ltb_opt *lopt;
   827		u64 rate64, ceil64;
   828		struct psched_ratecfg ratecfg, ceilcfg;
   829		u32 prio;
   830		int err;
   831	
 > 832		if (!opt)
   833			goto failure;
   834	
   835		err = nla_parse_nested_deprecated(tb, TCA_LTB_MAX, opt, ltb_policy,
   836						  NULL);
   837		if (err < 0)
   838			goto failure;
   839	
   840		err = -EINVAL;
   841		if (!tb[TCA_LTB_PARMS])
   842			goto failure;
   843	
   844		parent = parentid == TC_H_ROOT ? NULL : ltb_find_class(sch, parentid);
   845	
   846		lopt = nla_data(tb[TCA_LTB_PARMS]);
   847		if (!lopt->rate.rate || !lopt->ceil.rate)
   848			goto failure;
   849	
   850		rate64 = tb[TCA_LTB_RATE64] ? nla_get_u64(tb[TCA_LTB_RATE64]) : 0;
   851		ceil64 = tb[TCA_LTB_CEIL64] ? nla_get_u64(tb[TCA_LTB_CEIL64]) : 0;
   852		if (rate64 > ceil64)
   853			goto failure;
   854	
   855		psched_ratecfg_precompute(&ratecfg, &lopt->rate, rate64);
   856		psched_ratecfg_precompute(&ceilcfg, &lopt->ceil, ceil64);
   857		prio = lopt->prio;
   858		if (prio >= TC_LTB_NUMPRIO)
   859			prio = TC_LTB_NUMPRIO - 1;
   860	
   861		if (!cl) {
   862			if (!classid || TC_H_MAJ(classid ^ sch->handle) ||
   863			    ltb_find_class(sch, classid)) {
   864				err = -EINVAL;
   865				goto failure;
   866			}
   867			cl = ltb_alloc_class(sch, parent, classid, &ratecfg, &ceilcfg,
   868					     prio);
   869			if (!cl) {
   870				err = -ENOBUFS;
   871				goto failure;
   872			}
   873		} else {
   874			/* Modify existing class */
   875			ltb_modify_class(sch, cl, &ratecfg, &ceilcfg, prio);
   876		}
   877		qdisc_class_hash_grow(sch, &ltb->clhash);
   878		*arg = (unsigned long)cl;
   879		return 0;
   880	
   881	failure:
   882		return err;
   883	}
   884	

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org

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