linux-kernel - Re: [PATCH] dump_stack: convert generic dump

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Date:   Wed, 7 Mar 2018 11:57:35 +0100
From:   Arnd Bergmann <arnd@...db.de>
To:     Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
Cc:     Petr Mladek <pmladek@...e.com>, Tejun Heo <tj@...nel.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Dave Young <dyoung@...hat.com>,
        Andi Kleen <ak@...ux.intel.com>,
        Greentime Hu <green.hu@...il.com>,
        Vincent Chen <deanbo422@...il.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Stephen Rothwell <sfr@...b.auug.org.au>,
        adi-buildroot-devel@...ts.sourceforge.net,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>
Subject: Re: [PATCH] dump_stack: convert generic dump_stack into a weak symbol

On Wed, Mar 7, 2018 at 11:40 AM, Sergey Senozhatsky
<sergey.senozhatsky.work@...il.com> wrote:
> On (03/07/18 09:46), Arnd Bergmann wrote:
>> >
>> > When is this going to happen? 4.17?
>>
>> Originally I planned to wait a few more releases, but the last maintainer
>> has commented that he will now send a patch for immediate removal,
>> so 4.17 is almost certain at this point.
>
> Would be great to get it removed as soon as possible then. Otherwise we
> will get broken blackfin build errors from Stephen (or would need to hold
> off Dave's patch).

You could also add a patch to your tree that removes the blackfin
dump_stack() function, or we could ask Stephen and the other
people operating build bots to stop building blackfin right now
(they will have to do that anyway once the arch gets removed).

>> 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.
>
> Interesting point. Didn't check it. But I checked that we have at least
> one reference to lib/dump_stack from every arch so __weak could work its
> magic. The function is show_regs_print_info(). AFAICT, every arch calls
> it (we have it in lib/dump_stack now, so we will link with lib/dump_stack).
> Anyway, I'll be happy to drop my patch. Thanks for taking a look.

Ah, right, that is after your second patch. So after the first one, it might
be broken, but the follow-up patch fixes it.

Since lib/dump_stack.c is mandatory then, I would suggest making it
obj-y and moving it out of lib/ into kernel/printk/.

      Arnd