Re: net/sched/sch_fq.c:966:12: warning: stack frame size of 1400 bytes in function 'fq_dump'

[Nick Desaulniers <ndesaulniers@google.com>]

On Mon, Jun 15, 2020 at 9:17 AM 'Eric Dumazet' via Clang Built Linux
<clang-built-linux@googlegroups.com> wrote:
>
> On Sun, Jun 14, 2020 at 11:26 PM kernel test robot <lkp@intel.com> wrote:
> >
> > tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
> > head:   96144c58abe7ff767e754b5b80995f7b8846d49b
> > commit: 39d010504e6b4485d7ceee167743620dd33f4417 net_sched: sch_fq: add horizon attribute
> > date:   6 weeks ago
> > :::::: branch date: 3 hours ago
> > :::::: commit date: 6 weeks ago
> > config: arm-randconfig-r006-20200614 (attached as .config)
> > compiler: clang version 11.0.0 (https://github.com/llvm/llvm-project c669a1ed6386d57a75a602b53266466dae1e1d84)
> > 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 arm cross compiling tool for clang build
> >         # apt-get install binutils-arm-linux-gnueabi
> >         git checkout 39d010504e6b4485d7ceee167743620dd33f4417
> >         # save the attached .config to linux build tree
> >         COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross ARCH=arm
> >
> > If you fix the issue, kindly add following tag as appropriate
> > Reported-by: kernel test robot <lkp@intel.com>
> >
> > All warnings (new ones prefixed by >>, old ones prefixed by <<):
> >
> > >> net/sched/sch_fq.c:966:12: warning: stack frame size of 1400 bytes in function 'fq_dump' [-Wframe-larger-than=]
> > static int fq_dump(struct Qdisc *sch, struct sk_buff *skb)
> > ^
>
>
> This looks like a bug in CLANG on ARM, there is no way fq_dump() could
> consume so much stack space.

You can use
https://github.com/ClangBuiltLinux/frame-larger-than
to help debug these.  You might be surprised who's doing larger stack
allocations than expected.

>
>
>
> > 1 warning generated.
> >
> > # https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=39d010504e6b4485d7ceee167743620dd33f4417
> > git remote add linus https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
> > git remote update linus
> > git checkout 39d010504e6b4485d7ceee167743620dd33f4417
> > vim +/fq_dump +966 net/sched/sch_fq.c
> >
> > afe4fd062416b1 Eric Dumazet   2013-08-29   965
> > afe4fd062416b1 Eric Dumazet   2013-08-29  @966  static int fq_dump(struct Qdisc *sch, struct sk_buff *skb)
> > afe4fd062416b1 Eric Dumazet   2013-08-29   967  {
> > afe4fd062416b1 Eric Dumazet   2013-08-29   968          struct fq_sched_data *q = qdisc_priv(sch);
> > 48872c11b77271 Eric Dumazet   2018-11-11   969          u64 ce_threshold = q->ce_threshold;
> > 39d010504e6b44 Eric Dumazet   2020-05-01   970          u64 horizon = q->horizon;
> > afe4fd062416b1 Eric Dumazet   2013-08-29   971          struct nlattr *opts;
> > afe4fd062416b1 Eric Dumazet   2013-08-29   972
> > ae0be8de9a53cd Michal Kubecek 2019-04-26   973          opts = nla_nest_start_noflag(skb, TCA_OPTIONS);
> > afe4fd062416b1 Eric Dumazet   2013-08-29   974          if (opts == NULL)
> > afe4fd062416b1 Eric Dumazet   2013-08-29   975                  goto nla_put_failure;
> > afe4fd062416b1 Eric Dumazet   2013-08-29   976
> > 65c5189a2b57b9 Eric Dumazet   2013-11-15   977          /* TCA_FQ_FLOW_DEFAULT_RATE is not used anymore */
> > 65c5189a2b57b9 Eric Dumazet   2013-11-15   978
> > 48872c11b77271 Eric Dumazet   2018-11-11   979          do_div(ce_threshold, NSEC_PER_USEC);
> > 39d010504e6b44 Eric Dumazet   2020-05-01   980          do_div(horizon, NSEC_PER_USEC);
> > 48872c11b77271 Eric Dumazet   2018-11-11   981
> > afe4fd062416b1 Eric Dumazet   2013-08-29   982          if (nla_put_u32(skb, TCA_FQ_PLIMIT, sch->limit) ||
> > afe4fd062416b1 Eric Dumazet   2013-08-29   983              nla_put_u32(skb, TCA_FQ_FLOW_PLIMIT, q->flow_plimit) ||
> > afe4fd062416b1 Eric Dumazet   2013-08-29   984              nla_put_u32(skb, TCA_FQ_QUANTUM, q->quantum) ||
> > afe4fd062416b1 Eric Dumazet   2013-08-29   985              nla_put_u32(skb, TCA_FQ_INITIAL_QUANTUM, q->initial_quantum) ||
> > afe4fd062416b1 Eric Dumazet   2013-08-29   986              nla_put_u32(skb, TCA_FQ_RATE_ENABLE, q->rate_enable) ||
> > 76a9ebe811fb3d Eric Dumazet   2018-10-15   987              nla_put_u32(skb, TCA_FQ_FLOW_MAX_RATE,
> > 76a9ebe811fb3d Eric Dumazet   2018-10-15   988                          min_t(unsigned long, q->flow_max_rate, ~0U)) ||
> > f52ed89971adbe Eric Dumazet   2013-11-15   989              nla_put_u32(skb, TCA_FQ_FLOW_REFILL_DELAY,
> > f52ed89971adbe Eric Dumazet   2013-11-15   990                          jiffies_to_usecs(q->flow_refill_delay)) ||
> > 06eb395fa9856b Eric Dumazet   2015-02-04   991              nla_put_u32(skb, TCA_FQ_ORPHAN_MASK, q->orphan_mask) ||
> > 77879147a3481b Eric Dumazet   2016-09-19   992              nla_put_u32(skb, TCA_FQ_LOW_RATE_THRESHOLD,
> > 77879147a3481b Eric Dumazet   2016-09-19   993                          q->low_rate_threshold) ||
> > 48872c11b77271 Eric Dumazet   2018-11-11   994              nla_put_u32(skb, TCA_FQ_CE_THRESHOLD, (u32)ce_threshold) ||
> > 583396f4ca4d6e Eric Dumazet   2020-03-16   995              nla_put_u32(skb, TCA_FQ_BUCKETS_LOG, q->fq_trees_log) ||
> > 39d010504e6b44 Eric Dumazet   2020-05-01   996              nla_put_u32(skb, TCA_FQ_TIMER_SLACK, q->timer_slack) ||
> > 39d010504e6b44 Eric Dumazet   2020-05-01   997              nla_put_u32(skb, TCA_FQ_HORIZON, (u32)horizon) ||
> > 39d010504e6b44 Eric Dumazet   2020-05-01   998              nla_put_u8(skb, TCA_FQ_HORIZON_DROP, q->horizon_drop))
> > afe4fd062416b1 Eric Dumazet   2013-08-29   999                  goto nla_put_failure;
> > afe4fd062416b1 Eric Dumazet   2013-08-29  1000
> > d59b7d8059ddc4 Yang Yingliang 2014-03-12  1001          return nla_nest_end(skb, opts);
> > afe4fd062416b1 Eric Dumazet   2013-08-29  1002
> > afe4fd062416b1 Eric Dumazet   2013-08-29  1003  nla_put_failure:
> > afe4fd062416b1 Eric Dumazet   2013-08-29  1004          return -1;
> > afe4fd062416b1 Eric Dumazet   2013-08-29  1005  }
> > afe4fd062416b1 Eric Dumazet   2013-08-29  1006
> >
> > :::::: The code at line 966 was first introduced by commit
> > :::::: afe4fd062416b158a8a8538b23adc1930a9b88dc pkt_sched: fq: Fair Queue packet scheduler
> >
> > :::::: TO: Eric Dumazet <edumazet@google.com>
> > :::::: CC: David S. Miller <davem@davemloft.net>
> >
> > ---
> > 0-DAY CI Kernel Test Service, Intel Corporation
> > https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org
> > _______________________________________________
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>
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-- 
Thanks,
~Nick Desaulniers