linux-kernel - Re: [PATCH 4.19 088/323] locking/lockdep: Avoid RCU-induced noinstr fail

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Date:   Sun, 28 Nov 2021 12:59:22 +0100
From:   Salvatore Bonaccorso <carnil@...ian.org>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        Sasha Levin <sashal@...nel.org>
Subject: Re: [PATCH 4.19 088/323] locking/lockdep: Avoid RCU-induced noinstr
 fail

Hi,

On Sun, Nov 28, 2021 at 10:46:13AM +0100, Salvatore Bonaccorso wrote:
> Hi,
> 
> On Wed, Nov 24, 2021 at 12:54:38PM +0100, Greg Kroah-Hartman wrote:
> > From: Peter Zijlstra <peterz@...radead.org>
> > 
> > [ Upstream commit ce0b9c805dd66d5e49fd53ec5415ae398f4c56e6 ]
> > 
> > vmlinux.o: warning: objtool: look_up_lock_class()+0xc7: call to rcu_read_lock_any_held() leaves .noinstr.text section
> 
> For 4.19.218 at least this commit seems to cause a build failure for
> cpupower, if warnings are treated as errors, I have not seen the same
> for the 5.10.80 build:
> 
> gcc -g -O2 -fstack-protector-strong -Wformat -Werror=format-security -DVERSION=\"4.19\" -DPACKAGE=\"cpupower\" -DPACKAGE_BUGREPORT=\"Debian\ \(reportbug\ linux-cpupower\)\" -D_GNU_SOURCE -pipe -DNLS -Wall -Wchar-subscripts -Wpointer-arith
>  -Wsign-compare -Wno-pointer-sign -Wdeclaration-after-statement -Wshadow -Os -fomit-frame-pointer -fPIC -o /home/build/linux-4.19.218/debian/build/build-tools/tools/power/cpupower/lib/cpupower.o -c lib/cpupower.c
> In file included from lockdep.c:28:
> ../../../kernel/locking/lockdep.c: In function ‘look_up_lock_class’:
> ../../../kernel/locking/lockdep.c:694:2: error: implicit declaration of function ‘hlist_for_each_entry_rcu_notrace’; did you mean ‘hlist_for_each_entry_continue’? [-Werror=implicit-function-declaration]
>   hlist_for_each_entry_rcu_notrace(class, hash_head, hash_entry) {
>   ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>   hlist_for_each_entry_continue
> ../../../kernel/locking/lockdep.c:694:53: error: ‘hash_entry’ undeclared (first use in this function); did you mean ‘hash_ptr’?
>   hlist_for_each_entry_rcu_notrace(class, hash_head, hash_entry) {
>                                                      ^~~~~~~~~~
>                                                      hash_ptr
> ../../../kernel/locking/lockdep.c:694:53: note: each undeclared identifier is reported only once for each function it appears in
> ../../../kernel/locking/lockdep.c:694:64: error: expected ‘;’ before ‘{’ token
>   hlist_for_each_entry_rcu_notrace(class, hash_head, hash_entry) {
>                                                                 ^~
>                                                                 ;
> ../../../kernel/locking/lockdep.c:706:1: warning: control reaches end of non-void function [-Wreturn-type]
>  }
>  ^
> cc1: some warnings being treated as errors
> make[5]: *** [/home/build/linux-4.19.218/tools/build/Makefile.build:97: /home/build/linux-4.19.218/debian/build/build-tools/tools/lib/lockdep/lockdep.o] Error 1
> make[4]: *** [Makefile:121: /home/build/linux-4.19.218/debian/build/build-tools/tools/lib/lockdep/liblockdep-in.o] Error 2
> make[4]: Leaving directory '/home/build/linux-4.19.218/tools/lib/lockdep'
> make[3]: *** [/home/build/linux-4.19.218/debian/rules.d/tools/lib/lockdep/Makefile:16: all] Error 2
> make[3]: Leaving directory '/home/build/linux-4.19.218/debian/build/build-tools/tools/lib/lockdep'
> make[2]: *** [debian/rules.real:795: build-liblockdep] Error 2
> make[2]: *** Waiting for unfinished jobs....
> 
> I was not yet able to look further on it.

Might actually be a distro specific issue, needs some further
investigation.

Regards,
Salvatore