linux-kernel - Re: [RFC PATCH 5/5] GHES: Make NMI handler have a single reader

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Date:	Tue, 28 Apr 2015 09:38:20 +0200
From:	Borislav Petkov <bp@...en8.de>
To:	"Zheng, Lv" <lv.zheng@...el.com>
Cc:	linux-edac <linux-edac@...r.kernel.org>,
	Jiri Kosina <jkosina@...e.cz>, Borislav Petkov <bp@...e.de>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Len Brown <lenb@...nel.org>,
	"Luck, Tony" <tony.luck@...el.com>,
	Tomasz Nowicki <tomasz.nowicki@...aro.org>,
	"Chen, Gong" <gong.chen@...ux.intel.com>,
	Wolfram Sang <wsa@...-dreams.de>,
	Naoya Horiguchi <n-horiguchi@...jp.nec.com>,
	"linux-acpi@...r.kernel.org" <linux-acpi@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [RFC PATCH 5/5] GHES: Make NMI handler have a single reader

On Tue, Apr 28, 2015 at 02:24:16AM +0000, Zheng, Lv wrote:
> > > #APP
> > > # 177 "./arch/x86/include/asm/atomic.h" 1
> > > 	.pushsection .smp_locks,"a"
> > > .balign 4
> > > .long 671f - .
> > > .popsection
> > > 671:
> > > 	lock; cmpxchgl %edx,ghes_in_nmi(%rip)	# D.37056, MEM[(volatile u32 *)&ghes_in_nmi]
> > > # 0 "" 2
> > > #NO_APP
> > >
> > > And you need to atomic_dec() so that another reader can enter, i.e. how
> > > the exclusion primitive works.
> > >
> > > Or did you have something else in mind?
> > 
> > My mistake.
> > I mean cmpxchg() and xchg() (or atomic_cmpxchg() and atomic_xchg()) pair here, so nothing can be reduced.
> 
> Let me correct, it should be atomic_cmpxchg() and atomic_set() here as you only need to switch between 0 and 1.
> Sorry for the noise.

I still don't understand what you want from me here. You need to go into
more detail.

-- 
Regards/Gruss,
    Boris.

ECO tip #101: Trim your mails when you reply.
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