Re: Possible problem in check-local-export during the kernel build process (RCU torture)

[Zhouyi Zhou]

On Tue, Jun 28, 2022 at 3:25 PM Masahiro Yamada <masahiroy@xxxxxxxxxx> wrote:
>
> On Tue, Jun 28, 2022 at 9:55 AM Zhouyi Zhou <zhouzhouyi@xxxxxxxxx> wrote:
> >
> > Dear Masahiro:
> >
> > 1. The cause of the problem
> > When I am doing RCU torture test:
> >
> > #git clone https://kernel.source.codeaurora.cn/pub/scm/linux/kernel/git/paulmck/linux-rcu.git
> > #cd linux-rcu
> > #git checkout remotes/origin/pmladek.2022.06.15a
> > #./tools/testing/selftests/rcutorture/bin/torture.sh
> >
> > The kernel building report error something in both Dell PowerEdge R720
> > and Thinkpad T14 (Amd).
> >
> > For example:
> > /mnt/rcu/linux-rcu/tools/testing/selftests/rcutorture/res/2022.06.27-10.42.37-torture#
> > find . -name Make.out|xargs grep Error
> > ./results-rcutorture-kasan/RUDE01/Make.out:make[2]: ***
> > [scripts/Makefile.build:257: kernel/trace/power-traces.o] Error 255
>
>
> check-local-export stopped using the process substitution.
> Seet this commit:
>
>
> commit da4288b95baa1c7c9aa8a476f58b37eb238745b0
> Author: Masahiro Yamada <masahiroy@xxxxxxxxxx>
> Date:   Wed Jun 8 10:11:00 2022 +0900
>
>     scripts/check-local-export: avoid 'wait $!' for process substitution
>
>
>
>
> You are debugging the stale Kbuild code.
Thank Masahiro for your help
I patched da4288b95baa1c7c9aa8a476f58b37eb238745b0 to
pmladek.2022.06.15a branch of linux-rcu, after 13 hours' RCU torture
test,
all the testcases are built successfully!

Tested-by: Zhouyi Zhou <zhouzhouyi@xxxxxxxxx>
>
> If your main interest is RCU torture,
> please narrow it down to a standalone script,
> not the entire Kbuild.
OK and Thank you and Paul both for your guidance and encouragement ;-)
>
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> >
> > 2. I trace the problem to check-local-export
> > I add some echo statement in Makefile.build
> > diff --git a/scripts/Makefile.build b/scripts/Makefile.build
> > index 1f01ac65c0cd..0d48a2d3efff 100644
> > --- a/scripts/Makefile.build
> > +++ b/scripts/Makefile.build
> > @@ -227,13 +227,21 @@ cmd_check_local_export =
> > $(srctree)/scripts/check-local-export $@
> >
> >  define rule_cc_o_c
> >         $(call cmd_and_fixdep,cc_o_c)
> > +       echo "after fixdep $$? $<"
> >         $(call cmd,gen_ksymdeps)
> > +       echo "after gen_ksymdeps $$? $<"
> >         $(call cmd,check_local_export)
> > +       echo "after check_local_export $$? $<"
> >         $(call cmd,checksrc)
> > +       echo "after checksrc $$? $<"
> >         $(call cmd,checkdoc)
> > +       echo "after checkdoc $$? $<"
> >         $(call cmd,gen_objtooldep)
> > +       echo "after gen_objtooldep $$? $<"
> >         $(call cmd,gen_symversions_c)
> > +       echo "after gen_symversions $$? $<"
> >         $(call cmd,record_mcount)
> > +       echo "after record_mcount $$? $<"
> >  endef
> >
> > Then I rerun the torture.sh
> >
> > The result show it is check_local_export did not continue in all failed builds.
> >
> > 3. I trace into wait statement in check-local-export
> > diff --git a/scripts/check-local-export b/scripts/check-local-export
> > index da745e2743b7..d35477d95bdc 100755
> > --- a/scripts/check-local-export
> > +++ b/scripts/check-local-export
> > @@ -12,7 +12,7 @@ declare -A symbol_types
> >  declare -a export_symbols
> >
> >  exit_code=0
> > -
> > +echo "check-local-export L15 ${0} ${1}"
> >  while read value type name
> >  do
> >         # Skip the line if the number of fields is less than 3.
> > @@ -50,9 +50,10 @@ do
> >         #   done < <(${NM} --quiet ${1})
> >  done < <(${NM} ${1} 2>/dev/null || { echo "${0}: ${NM} failed" >&2; false; } )
> >
> > +echo "check-local-export L53 ${0} ${1}"
> >  # Catch error in the process substitution
> >  wait $!
> > -
> > +echo "check-local-export L56 ${0} ${1} $! $?"
> >  for name in "${export_symbols[@]}"
> >  do
> >         # nm(3) says "If lowercase, the symbol is usually local"
> > @@ -61,5 +62,9 @@ do
> >                 exit_code=1
> >         fi
> >  done
> > -
> > +if [ ${exit_code} -ne 0 ] ; then
> > +    echo "Zhouyi Zhou"
> > +    echo ${exit_code}
> > +fi
> > +echo "check-local-export L69 $? ${exit_code}"
> >  exit ${exit_code}
> >
> > Then I rerun the torture.sh
> >
> > The result show it is wait $! in all failed builds because in all failed cases,
> > there is L53, but no L56
> >
> > 4. I look into source code of wait command
> > #wget http://ftp.gnu.org/gnu/bash/bash-5.0.tar.gz
> > #tar zxf tar zxf bash-5.0.tar.gz
> > I found that there are QUIT statements in realization of function wait_for
> >
> > 5. My Guess
> > wait statement in check-local-export may cause bash to quit
> > I am very interested in this problem, but I am a rookie, I am very
> > glad to proceed the investigation with your further directions.
> >
> > Sorry to have brought you so much trouble.
> >
> >
> > Kind Regard
> > Thank you very much
> > Zhouyi
>
>
>
> --
> Best Regards
> Masahiro Yamada
Best Regards
Zhouyi