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Date: Thu, 3 Sep 2015 16:48:16 +0100
From: "Richard W.M. Jones" <rjones@redhat.com>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: Borislav Petkov <bp@alien8.de>, Chuck Ebbert <cebbert.lkml@gmail.com>,
        linux-kernel@vger.kernel.org, x86@kernel.org,
        Ingo Molnar <mingo@redhat.com>, "H. Peter Anvin" <hpa@zytor.com>
Subject: Re: [BUG 4.2-rc8] Interrupt occurs while apply_alternatives() is
 patching the handler
Message-ID: <20150903154816.GI29283@redhat.com>
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On Thu, Sep 03, 2015 at 12:41:47PM +0200, Thomas Gleixner wrote:
> On Thu, 3 Sep 2015, Borislav Petkov wrote:
> > On Wed, Sep 02, 2015 at 11:11:55AM +0200, Thomas Gleixner wrote:
> > >  static void __init_or_module add_nops(void *insns, unsigned int len)
> > >  {
> > > +	unsigned long flags;
> > > +
> > > +	local_irq_save(flags);
> > >  	while (len > 0) {
> > 
> > I guess you want to optimize the len==0 case to not disable interrupts
> > needlessly:
> > 
> > 	if (!len)
> > 		return;
> > 
> > 	local_irq_save(flags);
> > 	while (len > 0)
> > 		...
> 
> Nah. I rather put the local_irq_save into optimize_nops(). All other
> callers of add_nops() are operating on a buffer and use text_poke
> after that. Aside of that optimize_nops() is missing a sync_core().
> 
> Updated patch below.

The V2 patch has got to 900 iterations without hitting the problem.
As that is a lot more than without the patch, you can add:

  Tested-by: Richard W.M. Jones <rjones@redhat.com>

I will leave it going overnight just in case.

Thanks,

Rich.

-- 
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