From: Greentime Hu <green.hu@gmail.com>
To: Dave Young <dyoung@redhat.com>
Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
Petr Mladek <pmladek@suse.com>, Tejun Heo <tj@kernel.org>,
Stephen Rothwell <sfr@canb.auug.org.au>,
Linux-Next Mailing List <linux-next@vger.kernel.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Steven Rostedt <rostedt@goodmis.org>,
Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>,
akpm@linux-foundation.org, Andi Kleen <ak@linux.intel.com>
Subject: Re: linux-next: build failure after merge of the printk tree
Date: Mon, 5 Mar 2018 13:27:48 +0800 [thread overview]
Message-ID: <CAEbi=3dz8OE_8JBZ17ihP7=YQamPPK-qewVjtYv4ZEy4jHC6ww@mail.gmail.com> (raw)
In-Reply-To: <20180305032005.GA4661@dhcp-128-65.nay.redhat.com>
2018-03-05 11:20 GMT+08:00 Dave Young <dyoung@redhat.com>:
> On 03/03/18 at 11:47pm, Sergey Senozhatsky wrote:
>> Cc-ing Tejun
>>
>> On (03/02/18 16:54), Petr Mladek wrote:
>> [..]
>> > > (Though it is not immediately obvious why.)
>> >
>> > It is a mistery to me. The error appears when I move any of
>> > dump_stack_print_info() or show_regs_print_info() function
>> > definitions from kernel/printk/printk.c to lib/dump_stack.c.
>> > All the other changes seems unrelated.
>> >
>> > The thing is that we basically do not touch dump_stack() definition
>> > by that patch.
>>
>> Apparently dump_stack_print_info() was in lib/dump_stack.c a long
>> time ago, but it was deliberately moved to printk.c, when kernel gained
>> a "generic" (dummy) dump_stack() fallback. Some archs, like blackfin,
>> define their own dump_stack() symbol and make it global via EXPORT_SYMBOL.
>>
>> In case of blackfin that arch-specific dump_stack() symbol invokes a
>> global dump_stack_print_info(). If we move dump_stack_print_info() back
>> to lib/dump_stack.c then we link both with arch/blackfin/dumpstack.o
>> and lib/dump_stack.o, which results in multiple definitions error.
>> If we move dump_stack_print_info() out on libdump_stack.o, then we
>> never link with lib/dump_stack.o
>>
>> ... so what are we going to do with that.
>>
>> a) we can drop the patch and cherry pick only the kexec part
>>
>> b) we can try to mark dummy lib/dump_stack() as __weak
>> EXPORT_SYMBOL and remove EXPORT_SYMBOL from arch-specific
>> definitions.
>>
>> So we will end up with EXPORT_SYMBOL dump_stack() and archs
>> may re-define it. If some arch will accidentally mark its
>> own dump_stack() as EXPORT_SYMBOL then there should be a
>> linkage warning - a symbol is exported twice.
>>
>>
>> Something like below.
>>
>> Opinions? Will this work?
>
> I would think b) is better, thanks for the fix!
>
Hi,
b works in nds32.
Thanks for the fix :)
>>
>>
>> ========= 8< =========
>>
>> From: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
>> Subject: [PATCH] dump_stack: mark dummy dump_stack() as weak
>>
>> ---
>> arch/blackfin/kernel/dumpstack.c | 1 -
>> arch/nds32/kernel/traps.c | 2 --
>> lib/dump_stack.c | 4 ++--
>> 3 files changed, 2 insertions(+), 5 deletions(-)
>>
>> diff --git a/arch/blackfin/kernel/dumpstack.c b/arch/blackfin/kernel/dumpstack.c
>> index 3c992c1f8ef2..61af017130cd 100644
>> --- a/arch/blackfin/kernel/dumpstack.c
>> +++ b/arch/blackfin/kernel/dumpstack.c
>> @@ -174,4 +174,3 @@ void dump_stack(void)
>> show_stack(current, &stack);
>> trace_buffer_restore(tflags);
>> }
>> -EXPORT_SYMBOL(dump_stack);
>> diff --git a/arch/nds32/kernel/traps.c b/arch/nds32/kernel/traps.c
>> index 8828b4aeb72b..455bb0787367 100644
>> --- a/arch/nds32/kernel/traps.c
>> +++ b/arch/nds32/kernel/traps.c
>> @@ -166,8 +166,6 @@ void dump_stack(void)
>> __dump(NULL, base_reg);
>> }
>>
>> -EXPORT_SYMBOL(dump_stack);
>> -
>> void show_stack(struct task_struct *tsk, unsigned long *sp)
>> {
>> unsigned long *base_reg;
>> diff --git a/lib/dump_stack.c b/lib/dump_stack.c
>> index 5cff72f18c4a..9cf4465dbffa 100644
>> --- a/lib/dump_stack.c
>> +++ b/lib/dump_stack.c
>> @@ -85,7 +85,7 @@ static void __dump_stack(void)
>> #ifdef CONFIG_SMP
>> static atomic_t dump_lock = ATOMIC_INIT(-1);
>>
>> -asmlinkage __visible void dump_stack(void)
>> +asmlinkage __weak __visible void dump_stack(void)
>> {
>> unsigned long flags;
>> int was_locked;
>> @@ -118,7 +118,7 @@ asmlinkage __visible void dump_stack(void)
>> local_irq_restore(flags);
>> }
>> #else
>> -asmlinkage __visible void dump_stack(void)
>> +asmlinkage __weak __visible void dump_stack(void)
>> {
>> __dump_stack();
>> }
>> --
>> 2.16.2
>>
>
> Thanks
> Dave
next prev parent reply other threads:[~2018-03-05 5:27 UTC|newest]
Thread overview: 49+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-03-02 5:07 linux-next: build failure after merge of the printk tree Stephen Rothwell
2018-03-02 15:54 ` Petr Mladek
2018-03-03 2:43 ` Stephen Rothwell
2018-03-03 14:47 ` Sergey Senozhatsky
2018-03-05 3:20 ` Dave Young
2018-03-05 5:27 ` Greentime Hu [this message]
2018-03-05 5:41 ` Sergey Senozhatsky
2018-03-05 12:25 ` Petr Mladek
-- strict thread matches above, loose matches on Subject: below --
2023-01-15 23:23 Stephen Rothwell
2023-01-16 15:54 ` Petr Mladek
2022-11-21 0:00 Stephen Rothwell
2022-11-21 13:42 ` Petr Mladek
2021-07-20 7:43 Stephen Rothwell
2021-07-20 8:17 ` Naresh Kamboju
2021-07-20 12:28 ` Chris Down
2021-07-21 8:57 ` Petr Mladek
2021-07-21 11:22 ` Chris Down
2021-07-21 12:49 ` Petr Mladek
2021-07-22 23:01 ` Stephen Rothwell
2021-07-23 11:14 ` Petr Mladek
2021-07-23 12:14 ` Chris Down
2020-07-29 11:03 Stephen Rothwell
2020-07-29 11:47 ` Herbert Xu
2020-07-28 1:49 Stephen Rothwell
2020-07-28 1:51 ` Herbert Xu
2020-07-28 2:21 ` Stephen Rothwell
2020-07-28 1:54 ` Sergey Senozhatsky
2020-07-28 2:24 ` Stephen Rothwell
2020-06-21 3:15 Stephen Rothwell
2020-06-21 3:26 ` Herbert Xu
2020-06-23 0:26 ` Stephen Rothwell
2020-06-23 12:16 ` Petr Mladek
2020-06-23 12:19 ` Herbert Xu
2020-06-23 14:28 ` Petr Mladek
2020-06-23 15:17 ` Peter Zijlstra
2020-06-24 8:22 ` Petr Mladek
2020-06-24 0:20 ` Herbert Xu
2020-06-24 8:19 ` Petr Mladek
2020-06-24 8:21 ` Herbert Xu
2019-12-05 22:25 Stephen Rothwell
2019-12-06 10:03 ` Petr Mladek
2017-12-07 0:37 Stephen Rothwell
2017-12-07 1:26 ` Sergey Senozhatsky
2017-12-07 13:12 ` Petr Mladek
2017-12-06 3:23 Stephen Rothwell
2017-12-06 4:28 ` Sergey Senozhatsky
2017-12-06 10:17 ` Petr Mladek
2017-12-06 10:39 ` Sergey Senozhatsky
2017-12-07 1:24 ` Sergey Senozhatsky
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