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Message-ID: <CA+55aFwyVgLJq2OgKZBK7g+T5-_M4o+dnEAr+qtYxA5t_=HSvA@mail.gmail.com>
Date: Wed, 19 Feb 2014 12:17:15 -0800
From: Linus Torvalds <torvalds@...ux-foundation.org>
To: Waiman Long <waiman.long@...com>
Cc: Peter Zijlstra <peterz@...radead.org>,
"H. Peter Anvin" <hpa@...or.com>,
Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...hat.com>, Arnd Bergmann <arnd@...db.de>,
"linux-arch@...r.kernel.org" <linux-arch@...r.kernel.org>,
"the arch/x86 maintainers" <x86@...nel.org>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
Steven Rostedt <rostedt@...dmis.org>,
Andrew Morton <akpm@...ux-foundation.org>,
Michel Lespinasse <walken@...gle.com>,
Andi Kleen <andi@...stfloor.org>,
Rik van Riel <riel@...hat.com>,
"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
Raghavendra K T <raghavendra.kt@...ux.vnet.ibm.com>,
George Spelvin <linux@...izon.com>,
Tim Chen <tim.c.chen@...ux.intel.com>,
Daniel J Blueman <daniel@...ascale.com>,
Alexander Fyodorov <halcy@...dex.ru>,
Aswin Chandramouleeswaran <aswin@...com>,
Scott J Norton <scott.norton@...com>,
Thavatchai Makphaibulchoke <thavatchai.makpahibulchoke@...com>
Subject: Re: [PATCH v4 0/3] qspinlock: Introducing a 4-byte queue spinlock
On Wed, Feb 19, 2014 at 11:24 AM, Waiman Long <waiman.long@...com> wrote:
>
> We do have a CONFIG_PARAVIRT macro that turns on or off PV support. The
> queue spinlock can be easily changed into an unfair lock which allows lock
> stealing. We could have a config option to make it unfair in the PARAVIRT
> environment, but I don't think Linus like the idea of an unfair lock.
I could care less for the paravirt case. As long as the native case
ends up being sane (even when CONFIG_PARAVIRT is set at compile time),
I'm fine.
When actually running in a paravirtualized environment, locks are
always going to have problems.
Linus
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