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Date:   Thu, 21 Nov 2019 20:46:50 +0100
From:   Peter Zijlstra <peterz@infradead.org>
To:     Fenghua Yu <fenghua.yu@intel.com>
Cc:     Andy Lutomirski <luto@kernel.org>,
        David Laight <David.Laight@aculab.com>,
        Ingo Molnar <mingo@kernel.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        H Peter Anvin <hpa@zytor.com>,
        Tony Luck <tony.luck@intel.com>,
        Ashok Raj <ashok.raj@intel.com>,
        Ravi V Shankar <ravi.v.shankar@intel.com>,
        linux-kernel <linux-kernel@vger.kernel.org>, x86 <x86@kernel.org>
Subject: Re: [PATCH v10 6/6] x86/split_lock: Enable split lock detection by
 kernel parameter
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On Thu, Nov 21, 2019 at 10:53:03AM -0800, Fenghua Yu wrote:

> We are working on a separate patch set to fix all split lock issues
> in atomic bitops. Per Peter Anvin and Tony Luck suggestions:
> 1. Still keep the byte optimization if nr is constant. No split lock.
> 2. If type of *addr is unsigned long, do quadword atomic instruction
>    on addr. No split lock.
> 3. If type of *addr is unsigned int, do word atomic instruction
>    on addr. No split lock.
> 4. Otherwise, re-calculate addr to point the 32-bit address which contains
>    the bit and operate on the bit. No split lock.

Yeah, let's not do that. That sounds overly complicated for no real
purpose.