linux-kernel - Re: [PATCH 3/3] kref: Remove the memory barriers

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Date:	Tue, 13 Dec 2011 10:49:52 +0100
From:	Oliver Neukum <oneukum@...e.de>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Greg KH <greg@...ah.com>, Ming Lei <tom.leiming@...il.com>,
	gregkh@...e.de, akpm@...ux-foundation.org,
	linux-kernel@...r.kernel.org, ostrikov@...dia.com,
	adobriyan@...il.com, eric.dumazet@...il.com, mingo@...e.hu
Subject: Re: [PATCH 3/3] kref: Remove the memory barriers

Am Dienstag, 13. Dezember 2011, 10:12:20 schrieb Peter Zijlstra:
> On Mon, 2011-12-12 at 23:56 +0100, Oliver Neukum wrote:
> > I guess I worried not about the increment, but the decrement.
> > Which makes me wonder what happens if you don't intend
> > to get the kref again, but need to make sure it is usually freed,
> > like:
> > 
> > CPU A                                                           CPU B
> > 
> > kref_get(p)
> > start_io(p)
> >                                                                         [interrupt from IO]
> >                                                                         kref_put(p)
> 
> I would expect that if something was needed here, the io stack would
> provide the barriers since the io completion will probably want to
> change state set by the start_io thing.

> Anyway, I would put this squarely outside the responsibility of kref.

I agree, so let's remove it.

	Regards
		
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