lkml.org 
[lkml]   [2013]   [Feb]   [27]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH v4] drivers/tty: Folding Android's keyreset driver in sysRQ
On 13-02-27 09:57 AM, Linus Torvalds wrote:
> On Tue, Feb 26, 2013 at 11:33 PM, Dave Airlie <airlied@gmail.com> wrote:
>>
>> It looks to me like the weak bit isn't working so well
>>
>> if (platform_sysrq_reset_seq) {
>> for (i = 0; i < ARRAY_SIZE(sysrq_reset_seq); i++) {
>> key = platform_sysrq_reset_seq[i];
>> 6d: 66 8b 8c 00 00 00 00 mov 0x0(%eax,%eax,1),%cx
>> 74: 00
>>
>> is around where it craps out.
>> gcc version 4.7.2 20121109 (Red Hat 4.7.2-8) (GCC)
>> Fedora 18 machine.
>
> Hmm. I would love to blame gcc, but no, I think the code is crap.
>
> The whole 'platform_sysrq_reset_seq[]' thing is broken in current git,
> and it apparently only happens to work by mistake for most of us.
>
> Doing a "grep" for it shows all three uses:
>
> git grep platform_sysrq_reset_seq
>
> extern unsigned short platform_sysrq_reset_seq[] __weak;
> if (platform_sysrq_reset_seq) {
> key = platform_sysrq_reset_seq[i];
>
> and the thing is, if it is declared as an array (not a pointer), then
> I think it is perfectly understandable that when then testing the
> *address* of that array, gcc just says "you're stupid, you're testing
> something that cannot possibly be NULL, so I'll throw your idiotic
> test away".
>
> And gcc would be completely correct. That test is moronic. You just
> said that platform_sysrq_reset_seq[] was an external array, there is
> no way in hell that is NULL.
>
> Now, if it was a _pointer_, that would be a different thing entirely.
> A pointer can have a NULL value. A named array, not so much.
>
> So I *think* the fix might be something like the attached. Totally
> untested. It may compile, or it may not.
>
> Linus
>

Your fix is compiling, running and yielding the correct results -
apologies about that.

Acked-by: Mathieu Poirier <mathieu.poirier@linaro.org>


\
 
 \ /
  Last update: 2013-02-28 03:41    [W:1.450 / U:0.312 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site