linux-kernel - Re: [PATCH 12/29] x86, tsx: Add a per thread transaction disable count

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Message-ID: <20130323173238.GA13379@pd.tnic>
Date:	Sat, 23 Mar 2013 18:32:38 +0100
From:	Borislav Petkov <bp@...en8.de>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Andi Kleen <andi@...stfloor.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	the arch/x86 maintainers <x86@...nel.org>,
	Andi Kleen <ak@...ux.intel.com>
Subject: Re: [PATCH 12/29] x86, tsx: Add a per thread transaction disable
 count

On Sat, Mar 23, 2013 at 10:16:28AM -0700, Linus Torvalds wrote:
> On Sat, Mar 23, 2013 at 8:52 AM, Borislav Petkov <bp@...en8.de> wrote:
> >
> > Really? Let's see:
> 
> Your test seems to assume that a single bit is sufficient, which
> sounds unlikely. If you have any kind of nesting going on, you need
> more than one bit. Then add/sub isn't a single "xor" of a bit any
> more.

Right, but does nesting even apply here? I mean, AFAICR the commit
message, we're talking about per-thread transaction disabling. IOW, this
is an on/off button used in a boolean context.

Or is this going to be used as a mechanism to tisable TSX when max
nesting level has been reached?

Hmmm.

Btw, the disable/reenable_txn() aren't used anywhere in the patchset and
I'd actually like to get an idea where/how those are used.

Thanks.

-- 
Regards/Gruss,
    Boris.

Sent from a fat crate under my desk. Formatting is fine.
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