linux-kernel - Re: [PATCH 2/2] kprobes: check CONFIG_FREEZER instead of CONFIG

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Message-ID: <4991A349.8090005@redhat.com>
Date:	Tue, 10 Feb 2009 10:54:49 -0500
From:	Masami Hiramatsu <mhiramat@...hat.com>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
CC:	Ingo Molnar <mingo@...e.hu>, Len Brown <lenb@...nel.org>,
	pm list <linux-pm@...ts.linux-foundation.org>,
	Pavel Machek <pavel@...e.cz>,
	LKML <linux-kernel@...r.kernel.org>,
	Cheng Renquan <crquan@...il.com>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH 2/2] kprobes: check CONFIG_FREEZER instead of CONFIG_PM

Rafael J. Wysocki wrote:
> On Tuesday 10 February 2009, Ingo Molnar wrote:
>> * Masami Hiramatsu <mhiramat@...hat.com> wrote:
>>
>>> Ingo Molnar wrote:
>>>> * Len Brown <lenb@...nel.org> wrote:
>>>>
>>>>>>> Check CONFIG_FREEZER instead of CONFIG_PM because kprobe booster
>>>>>>> depends on freeze_processes() and thaw_processes() when CONFIG_PREEMPT=y.
>>>>>>>
>>>>>>> This fixes a linkage error which occurs when CONFIG_PREEMPT=y, CONFIG_PM=y
>>>>>>> and CONFIG_FREEZER=n.
>>>>>>>
>>>>>>> Reported-by: Cheng Renquan <crquan@...il.com>
>>>>>>> Signed-off-by: Masami Hiramatsu <mhiramat@...hat.com>
>>>>>>> Signed-off-by: Rafael J. Wysocki <rjw@...k.pl>
>>>>>>> ---
>>>>>>>  arch/ia64/kernel/kprobes.c |    2 +-
>>>>>>>  arch/x86/kernel/kprobes.c  |    2 +-
>>>>>>>  kernel/kprobes.c           |    2 +-
>>>>>>>  3 files changed, 3 insertions(+), 3 deletions(-)
>>>>>> looks good, the x86 bits:
>>>>>>
>>>>>> Acked-by: Ingo Molnar <mingo@...e.hu>
>>>>> man, we have too many config options:-)
>>>> the non-x86 bits (kernel/kprobes.c) are crappy though, and broke -rc4
>>>> allnoconfig:
>>>>
>>>> kernel/built-in.o: In function `collect_garbage_slots':
>>>> kprobes.c:(.kprobes.text+0x16e4): undefined reference to `freeze_processes'
>>>> kprobes.c:(.kprobes.text+0x16f2): undefined reference to `thaw_processes'
>>>> kprobes.c:(.kprobes.text+0x176b): undefined reference to `thaw_processes'
>>> Hmm, it seems that kernel/power/built-in.o was not linked to .tmp_vmlinux1.
>>>
>>>   ld -m elf_i386 --build-id -o .tmp_vmlinux1 -T arch/x86/kernel/vmlinux.lds
>>> arch/x86/kernel/head_32.o arch/x86/kernel/head32.o arch/x86/kernel/head.o
>>> arch/x86/kernel/init_task.o  init/built-in.o --start-group  usr/built-in.o
>>> arch/x86/kernel/built-in.o  arch/x86/mm/built-in.o  arch/x86/mach-default/built-in.o
>>> arch/x86/crypto/built-in.o  arch/x86/vdso/built-in.o  kernel/built-in.o
>>> mm/built-in.o  fs/built-in.o  ipc/built-in.o  security/built-in.o  crypto/built-in.o
>>> block/built-in.o  lib/lib.a  arch/x86/lib/lib.a  lib/built-in.o
>>> arch/x86/lib/built-in.o  drivers/built-in.o  sound/built-in.o  firmware/built-in.o
>>> arch/x86/pci/built-in.o  net/built-in.o --end-group
>>> kernel/built-in.o: In function `collect_garbage_slots':
>>> kprobes.c:(.kprobes.text+0x16e4): undefined reference to `freeze_processes'
>>> kprobes.c:(.kprobes.text+0x16f2): undefined reference to `thaw_processes'
>>> kprobes.c:(.kprobes.text+0x176b): undefined reference to `thaw_processes'
>>>
>>> At kernel/Makefile:53, I can see
>>>
>>> obj-$(CONFIG_PM) += power/
>>>
>>> but CONFIG_PM was not set in config
>> Sounds plausible. We need a fix for this - it's broken upstream.
> 
> Hmm.  Can || be used under obj-$() ?

I think just adding a line "obj-$(CONFIG_FREEZER) += power/" is enough.
(you can see similar lines of "trace/" at the bottom of obj- lines
 in kernel/Makefile )

Thanks,

> 
> Rafael

-- 
Masami Hiramatsu

Software Engineer
Hitachi Computer Products (America) Inc.
Software Solutions Division

e-mail: mhiramat@...hat.com

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