lkml.org 
[lkml]   [2009]   [Feb]   [19]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH] x86: remove unneeded endless loop in BUG()

* H. Peter Anvin <hpa@zytor.com> wrote:

> Ingo Molnar wrote:
>>
>> the problem is that the DO_BUG() will generate the u2d instruction into
>> a random place where GCC puts it. It certainly wont be in the place
>> where the __bug_table logic above expects it.
>>
>> The result will be cryptic crashes instead of a clean BUG message
>> assert.
>>
>
> I went and talked to H.J. Lu about this.
>
> He said __builtin_trap(); is functionally treated as an asm volatile,
> and that it is most likely impossible that gcc could do anything wrong
> here (he did specifically state that nothing can move across the asm
> volatile, and there are no data dependencies between the asm volatile
> and the __builtin_trap).
>
> He also agreed that the right way to do this is __builtin_not_reached(),
> and I promised to submit a feature request for this for a future version
> of gcc.
>
> Given that, I would suggest we back out the patch, and that when
> __builtin_not_reached(); is supported, we can simply do:
>
> #if __GNUC__ is recent enough
> # define not_reached() __builtin_not_reached()
> #else
> # define not_reached() for(;;)
> #endif
>
> OK?

Yeah, sounds good!

Ingo


\
 
 \ /
  Last update: 2009-02-19 21:35    [W:0.187 / U:0.336 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site