Re: [tip:perf/uprobes] uprobes/core: Clean up, refactor and improvethe code

[Ingo Molnar]

* Srikar Dronamraju <srikar@xxxxxxxxxxxxxxxxxx> wrote:

> * Ingo Molnar <mingo@xxxxxxx> [2012-02-20 08:38:23]:
> 
> > 
> > * Srikar Dronamraju <srikar@xxxxxxxxxxxxxxxxxx> wrote:
> > 
> > > The volatiles were added to arch/x86/kernel/kprobes.c because 
> > > of commit 7115e3fcf45 and 315eb8a2a1b. The volatiles are 
> > > required because gcc 4.6 gave a warning about the asm operand 
> > > for test_bit.  So the same were added to 
> > > arch/x86/kernel/uprobes.c.
> > 
> > Seems like a GCC bug - a bogus warning - or does it generate bad 
> > code as well?
> 
> Yes it is a gcc bug and was fixed by Jakub.
> As per Josh, only the first long is output if compiled on the buggy gcc.

That's an important piece of information - the more reason to 
document the quirk.

> > In any case, kprobes.c did it correctly, it added the volatile 
> > *and a comment*, pointing out that it's a GCC bug. No such 
> > warning was added to uprobes.c, making the volatile look 
> > entirely spurious.
> 
> okay. 

Thanks,

	Ingo
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