Re: [PATCH] WARN_ONCE(): use bool for boolean flag

[Cesar Eduardo Barros]

Daniel Walker escreveu:
> On Sun, 2009-09-27 at 14:24 -0300, Cesar Eduardo Barros wrote:
>
> > I took a quick look, and all uses seem to be directly in a boolean 
> > context (within an if()), so there would be no problem. Besides, the 
> > unlikely() all these macros end with does a double negation, meaning 
> > even if it is an int, it will be either 0 or 1 (but I am not sure I am 
> > reading these macros right - it seems CONFIG_TRACE_BRANCH_PROFILING 
> > turns all unlikely() into likely()).
> >
> > In fact, I was expecting no change at all, since gcc should be able to 
> > see it is being treated as a boolean (perhaps I am trusting gcc too 
> > much). And to make matters even more confusing, my own test changing all 
> > __ret_warn_once to bool and dropping the !! caused an _increase_ of 598 
> > bytes (x86-64 defconfig).
> >
> >     text    data     bss     dec     hex filename
> > 8100553 1207148  991988 10299689         9d2929 vmlinux.warnret.before
> > 8101119 1207180  991988 10300287         9d2b7f vmlinux.warnret.after
> >
> > (And yes, data increased again.)
>
> Did you have the CONFIG_TRACE_BRANCH_PROFILING option enabled for the
> test above?

CONFIG_BRANCH_PROFILE_NONE=y

CONFIG_TRACE_BRANCH_PROFILING does not even appear in the .config.

> If this was just your regular base line config , then that is odd .. I
> also would think worse case would be no size reduction .. I did my
> compile test on x86-32 btw..

Yes, it is very odd. And I tried compiling a small test module to see if 
I could see the changes in the assembly output:

#include <linux/module.h>
#include <linux/kernel.h>

void test(int value)
{
        WARN_ON_ONCE(value);
}
EXPORT_SYMBOL_GPL(test);

But the assembly output is identical.

I will try looking at the first function which shows a difference in 
size (which appears to be handle_irq) and see what I can find.

--
Cesar Eduardo Barros
cesarb@xxxxxxxxxx
cesar.barros@xxxxxxxxx
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