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

On Sun, Nov 28, 2021 at 02:06:30PM +0100, Greg Kroah-Hartman wrote:

On Sun, Nov 28, 2021 at 01:11:11PM +0100, Salvatore Bonaccorso wrote:

quoted

Hi,

On Sun, Nov 28, 2021 at 12:59:24PM +0100, Salvatore Bonaccorso wrote:

quoted

Hi,

On Sun, Nov 28, 2021 at 10:46:13AM +0100, Salvatore Bonaccorso wrote:

quoted

Hi,

On Wed, Nov 24, 2021 at 12:54:38PM +0100, Greg Kroah-Hartman wrote:

quoted

From: Peter Zijlstra <peterz@infradead.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.

I'm really sorry about the doubled noice, so here is the stance. I can
reproduce distro indpeendent, but the initial claim was wrong. It can
be reproduced for 4.19.218:

$ LC_ALL=C.UTF-8 V=1 ARCH=x86 make -C tools liblockdep
make: Entering directory '/home/build/linux-stable/tools'
mkdir -p lib/lockdep && make  subdir=lib/lockdep  -C lib/lockdep 
make[1]: Entering directory '/home/build/linux-stable/tools/lib/lockdep'
make -f /home/build/linux-stable/tools/build/Makefile.build dir=. obj=fixdep
  gcc -Wp,-MD,./.fixdep.o.d -Wp,-MT,fixdep.o  -D"BUILD_STR(s)=#s"   -c -o fixdep.o fixdep.c
   ld -r -o fixdep-in.o  fixdep.o
gcc  -o fixdep fixdep-in.o
  gcc -Wp,-MD,./.common.o.d -Wp,-MT,common.o -g -DCONFIG_LOCKDEP -DCONFIG_STACKTRACE -DCONFIG_PROVE_LOCKING -DBITS_PER_LONG=__WORDSIZE -DLIBLOCKDEP_VERSION='"4.19.218"' -rdynamic -O0 -g -fPIC -Wall -I. -I./uinclude -I./include -I../../include -D"BUILD_STR(s)=#s" -c -o common.o common.c
  gcc -Wp,-MD,./.lockdep.o.d -Wp,-MT,lockdep.o -g -DCONFIG_LOCKDEP -DCONFIG_STACKTRACE -DCONFIG_PROVE_LOCKING -DBITS_PER_LONG=__WORDSIZE -DLIBLOCKDEP_VERSION='"4.19.218"' -rdynamic -O0 -g -fPIC -Wall -I. -I./uinclude -I./include -I../../include -D"BUILD_STR(s)=#s" -c -o lockdep.o lockdep.c
In file included from lockdep.c:28:
../../../kernel/locking/lockdep.c: In function ‘look_up_lock_class’:
../../../kernel/locking/lockdep.c:692:2: warning: implicit declaration of function ‘hlist_for_each_entry_rcu_notrace’; did you mean ‘hlist_for_each_entry_continue’? [-Wimplicit-function-declaration]
  hlist_for_each_entry_rcu_notrace(class, hash_head, hash_entry) {
  ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  hlist_for_each_entry_continue
../../../kernel/locking/lockdep.c:692:53: 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:692:53: note: each undeclared identifier is reported only once for each function it appears in
../../../kernel/locking/lockdep.c:692:64: error: expected ‘;’ before ‘{’ token
  hlist_for_each_entry_rcu_notrace(class, hash_head, hash_entry) {
                                                                ^~
                                                                ;
../../../kernel/locking/lockdep.c:704:1: warning: control reaches end of non-void function [-Wreturn-type]
 }
 ^
make[2]: *** [/home/build/linux-stable/tools/build/Makefile.build:97: lockdep.o] Error 1
make[1]: *** [Makefile:121: liblockdep-in.o] Error 2
make[1]: Leaving directory '/home/build/linux-stable/tools/lib/lockdep'
make: *** [Makefile:66: liblockdep] Error 2
make: Leaving directory '/home/build/linux-stable/tools'

Reverting upstream ce0b9c805dd6 ("locking/lockdep: Avoid RCU-induced
noinstr fail") on top of 4.19.218 fixes the issue.

So back to square one, and again apologies for the intermediate noise!

What config/arch is causing this to break?  And if you add rchlist.h to
the include files for lockdep.c, does that resolve the issue?  I haven't
seen any other reports of this yet.

Ah, it's the tools being built here, sorry, that was confusing.

Yes, I can duplicate this, when building liblockdep.  As that code just
got ripped out of upstream, perhaps just use the out-of-tree code
instead now?

thanks,

greg k-h