On Wed, Mar 7, 2018 at 10:44 AM, Greentime Hu <green...@gmail.com> wrote: > 2018-03-07 17:09 GMT+08:00 Petr Mladek <pmla...@suse.com>: >> Ah, there was a mid-air collision. Arnd already answered most of my >> questions and even more. >> >> On Wed 2018-03-07 09:46:27, Arnd Bergmann wrote: >>> On Wed, Mar 7, 2018 at 3:21 AM, Sergey Senozhatsky >>> <sergey.senozhatsky.w...@gmail.com> wrote: >>> > On (03/06/18 14:27), Arnd Bergmann wrote: >>> >> Weak symbols are generally discouraged in the kernel. We have >>> >> them in a couple of places, but I find them rather confusing as they >>> >> make it harder to figure out what is actually going on. >>> > >>> > Honestly, I kind of find __weak less confusing than >>> > EXPORT_SYMBOL(dump_stack) >>> > in 3 different places. __weak hints that the symbol likely will be >>> > overridden >>> > somewhere, while EXPORT_SYMBOL() does not (at least not to me). Dunno. >>> >>> It's not either/or, they are both wrong ;-) >>> >>> The EXPORT_SYMBOL() is not the thing that makes it work. The duplicate >>> declaration today only works because lib/dump_stack.o is listed as lib-y >>> in the Makefile instead of obj-y. On blackfin and nds32, this causes the >>> entire >>> file to just not be included in the final vmlinux, because there are no >>> references to it. >>> >>> With your patch, I would actually expect the lib/dump_stack.o file >>> to still not be picked up, so now you have a missing EXPORT_SYMBOL() >>> on the two unusual architectures until the point when you add another >>> (referenced) symbol to it. >> >> Great catch! We should change it from lib-y to obj-y. Of course, >> the best solution would be if nds32 uses the generic implementation >> and we could avoid adding __weak. >> > > I agree too. > I think I can add a patch to remove the dump_stack() implementation in > nds32 and use the generic one.
Looks good, Acked-by: Arnd Bergmann <a...@arndb.de> > diff --git a/arch/nds32/kernel/traps.c b/arch/nds32/kernel/traps.c > index 8828b4aeb72b..6e34eb9824a4 100644 > --- a/arch/nds32/kernel/traps.c > +++ b/arch/nds32/kernel/traps.c > @@ -156,18 +156,6 @@ static void __dump(struct task_struct *tsk, > unsigned long *base_reg) > pr_emerg("\n"); > } > > -void dump_stack(void) > -{ > - unsigned long *base_reg; > - if (!IS_ENABLED(CONFIG_FRAME_POINTER)) > - __asm__ __volatile__("\tori\t%0, $sp, #0\n":"=r"(base_reg)); > - else > - __asm__ __volatile__("\tori\t%0, $fp, #0\n":"=r"(base_reg)); > - __dump(NULL, base_reg); > -} > - > -EXPORT_SYMBOL(dump_stack); > -