Re: [PATCH] asm-generic: Use raw_local_irq_save/restore instead local_irq_save/restore

[Michal Simek]

This is a multi-part message in MIME format.Andrew Morton wrote:
> On Wed, 26 May 2010 10:42:43 -0400 Steven Rostedt <rostedt@xxxxxxxxxxx> wrote:
>
> > On Wed, 2010-05-26 at 10:48 +0200, monstr@xxxxxxxxx wrote:
> > > From: Michal Simek <monstr@xxxxxxxxx>
> > >
> > > start/stop_critical_timing function for preemptirqsoff, preemptoff
> > > and irqsoff tracers contains atomic_inc and atomic_dec operations.
> > >
> > > Atomic operations used local_irq_save/restore macros to ensure
> > > atomic access but they are traced by the same function which is causing
> > > recursion problem.
> > >
> > > The reason is when these tracers are turn ON then local_irq_save/restore
> > > macros are changed in include/linux/irqflags.h to call trace_hardirqs_on/off
> > > which call start/stop_critical_timing.
> > >
> > > Microblaze was affected because use generic atomic implementation.
> > >
> > > Signed-off-by: Michal Simek <monstr@xxxxxxxxx>
> > Acked-by: Steven Rostedt <rostedt@xxxxxxxxxxx>
>
> Sighed-at-by: me.
>
> > > diff --git a/include/asm-generic/atomic.h b/include/asm-generic/atomic.h
> > > index 058129e..6c190fd 100644
> > > --- a/include/asm-generic/atomic.h
> > > +++ b/include/asm-generic/atomic.h
> > > @@ -57,11 +57,11 @@ static inline int atomic_add_return(int i, atomic_t *v)
> > >  	unsigned long flags;
> > >  	int temp;
> > >  
> > > -	local_irq_save(flags);
> > > +	raw_local_irq_save(flags);
> > >  	temp = v->counter;
> > >  	temp += i;
> > >  	v->counter = temp;
> > > -	local_irq_restore(flags);
> > > +	raw_local_irq_restore(flags);
> > >  
> > >  	return temp;
> > >  }
>
> If a developer looks at atomic_add_return() and asks himself "why did
> this use raw_local_irq_save()", the only way of answering that question
> is to go groveling through the git logs, which is a right PITA if
> you're trying to get some coding work done.
>
> Guys, any time you add code which is non-obvious at the raw C level, it
> *needs* a comment!

Andrew: Can you please add this patch to your tree? I have it in 
microblaze next branch but should go through different tree.

Thanks,
Michal

--
Michal Simek, Ing. (M.Eng)
w: www.monstr.eu p: +42-0-721842854
Maintainer of Linux kernel 2.6 Microblaze Linux - http://www.monstr.eu/fdt/
Microblaze U-BOOT custodian