linux-kernel - Re: [v4.6-rc7-183-g1410b74e4061]

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Date:	Mon, 16 May 2016 20:11:51 +0200
From:	Sedat Dilek <sedat.dilek@...il.com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Ingo Molnar <mingo@...nel.org>, David Miller <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"the arch/x86 maintainers" <x86@...nel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [v4.6-rc7-183-g1410b74e4061]

On 5/16/16, Peter Zijlstra <peterz@...radead.org> wrote:
> On Mon, May 16, 2016 at 07:42:35PM +0200, Sedat Dilek wrote:
>
>> Unfortunately, I could not reproduce this again with none of my
>> 183-kernels.
>> When I first hit a "chain_key collision" issue, it was hard to redproduce,
>> so.
>> Any idea, how I can "force" this?
>
> Nope; I wish I knew, that'd be so much easier to work with :/
>
> I'm hoping someone will report a reproducer, even something that
> triggers once every 5-10 runs would be awesome.
>
> In any case, like I've explained before, nothing regressed as such, we
> only added this new warning under DEBUG_LOCKDEP because we want to
> better understand the condition that triggers it.
>
> If it bothers you, just turn off DEBUG_LOCKDEP and know that your kernel
> is as reliable as it was before. OTOH, if you do keep it on, please
> let me know if you can (semi) reliably trigger this, as I'd really like
> to have a better understanding.
>

OK, I keep checking my logs.

I refreshed your patch Ingo pointed me to.

But it fails like this (on top of Linux v4.6 final)...
[...]
  if [ "" = "-pg" ]; then if [ kernel/locking/mutex-debug.o !=
"scripts/mod/empty.o" ]; then ./scripts/recordmcount
"kernel/locking/mutex-debug.o"; fi; fi;
  mycompiler -Wp,-MD,kernel/locking/.lockdep.o.d  -nostdinc -isystem
/usr/lib/gcc/x86_64-linux-gnu/4.9/include -nostdinc -isystem
/usr/lib/gcc/x86_64-linux-gnu/4.9/include -I./arch/x86/include
-Iarch/x86/include/generated/uapi -Iarch/x86/include/generated
-Iinclude -I./arch/x86/include/uapi -Iarch/x86/include/generated/uapi
-I./include/uapi -Iinclude/generated/uapi -include
./include/linux/kconfig.h -D__KERNEL__ -Wall -Wundef
-Wstrict-prototypes -Wno-trigraphs -fno-strict-aliasing -fno-common
-Werror-implicit-function-declaration -Wno-format-security -std=gnu89
-mno-sse -mno-mmx -mno-sse2 -mno-3dnow -mno-avx -m64 -falign-jumps=1
-falign-loops=1 -mno-80387 -mno-fp-ret-in-387
-mpreferred-stack-boundary=3 -mtune=generic -mno-red-zone
-mcmodel=kernel -funit-at-a-time -maccumulate-outgoing-args
-DCONFIG_X86_X32_ABI -DCONFIG_AS_CFI=1 -DCONFIG_AS_CFI_SIGNAL_FRAME=1
-DCONFIG_AS_CFI_SECTIONS=1 -DCONFIG_AS_FXSAVEQ=1 -DCONFIG_AS_SSSE3=1
-DCONFIG_AS_CRC32=1 -DCONFIG_AS_AVX=1 -DCONFIG_AS_AVX2=1 -pipe
-Wno-sign-compare -fno-asynchronous-unwind-tables
-fno-delete-null-pointer-checks -O2 --param=allow-store-data-races=0
-Wframe-larger-than=1024 -fno-stack-protector
-Wno-unused-but-set-variable -fno-omit-frame-pointer
-fno-optimize-sibling-calls -fno-var-tracking-assignments -mfentry
-DCC_USING_FENTRY -Wdeclaration-after-statement -Wno-pointer-sign
-fno-strict-overflow -fconserve-stack -Werror=implicit-int
-Werror=strict-prototypes -Werror=date-time -DCC_HAVE_ASM_GOTO
-D"KBUILD_STR(s)=#s" -D"KBUILD_BASENAME=KBUILD_STR(lockdep)"
-D"KBUILD_MODNAME=KBUILD_STR(lockdep)" -c -o
kernel/locking/.tmp_lockdep.o kernel/locking/lockdep.c
kernel/locking/lockdep.c: In function 'print_chain_keys_held_locks':
kernel/locking/lockdep.c:2034:2: error: too few arguments to function
'print_chain_key_iteration'
  print_chain_key_iteration(hlock_next->class_idx, chain_key);
  ^
kernel/locking/lockdep.c:2006:12: note: declared here
 static u64 print_chain_key_iteration(int class_idx, u64 chain_key,
u64 prev_key)
            ^
make[4]: *** [kernel/locking/lockdep.o] Error 1
make[3]: *** [kernel/locking] Error 2
make[2]: *** [kernel] Error 2
[...]

- Sedat -

View attachment "0001-locking-lockdep-Some-more-additional-chain_key-colli.patch" of type "text/x-diff" (4975 bytes)