linux-kernel - Re: [PATCH -rt] ARM TLB flush fix: don't forget to re-enable preemption

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Message-ID: <20070523092232.GA9482@flint.arm.linux.org.uk>
Date:	Wed, 23 May 2007 10:22:32 +0100
From:	Russell King <rmk+lkml@....linux.org.uk>
To:	Kevin Hilman <khilman@...sta.com>
Cc:	Daniel Walker <dwalker@...sta.com>, Ingo Molnar <mingo@...e.hu>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH -rt] ARM TLB flush fix: don't forget to re-enable preemption

On Tue, May 22, 2007 at 04:41:36PM -0700, Kevin Hilman wrote:
> On Tue, 2007-05-22 at 16:25 -0700, Daniel Walker wrote:
> > On Tue, 2007-05-22 at 16:01 -0700, Kevin Hilman wrote:
> > > Add a preempt_enable() to flush_tlb_kernel_page() since -rt4 patch
> > > adds a preempt_disable but no preempt_enable().
> > > 
> > > Signed-off-by: Kevin Hilman <khilman@...sta.com>
> > > 
> > > 
> > > ---
> > >  include/asm-arm/tlbflush.h |    1 +
> > >  1 file changed, 1 insertion(+)
> > > 
> > > Index: linux-2.6.21/include/asm-arm/tlbflush.h
> > > ===================================================================
> > > --- linux-2.6.21.orig/include/asm-arm/tlbflush.h
> > > +++ linux-2.6.21/include/asm-arm/tlbflush.h
> > > @@ -378,6 +378,7 @@ static inline void local_flush_tlb_kerne
> > >  		asm("mcr p15, 0, %0, c8, c6, 1" : : "r" (kaddr) : "cc");
> > >  	if (tlb_flag(TLB_V6_I_PAGE))
> > >  		asm("mcr p15, 0, %0, c8, c5, 1" : : "r" (kaddr) : "cc");
> > 
> > Aren't these mcr operations atomic?
> > 
> 
> Individually, yes.  But the point of the preempt_disable/enable is to
> make the whole sequence atomic.

In which case shouldn't it be at the end of the function so it includes
the write buffer handling as well?

However, I think I agree with Daniel on this one.  I don't see the point
of the preempt_disable() here.

-- 
Russell King
 Linux kernel    2.6 ARM Linux   - http://www.arm.linux.org.uk/
 maintainer of:
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