linux-kernel - Re: [PATCH v2 2/4] MIPS: Introduce config options for LLSC availability

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Date: Fri, 21 Jun 2024 22:31:21 +0200
From: Thomas Bogendoerfer <tsbogend@...ha.franken.de>
To: Jiaxun Yang <jiaxun.yang@...goat.com>
Cc: "Maciej W. Rozycki" <macro@...am.me.uk>,
	Jonas Gorski <jonas.gorski@...il.com>,
	"linux-mips@...r.kernel.org" <linux-mips@...r.kernel.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 2/4] MIPS: Introduce config options for LLSC
 availability

On Fri, Jun 21, 2024 at 04:21:49PM +0100, Jiaxun Yang wrote:
> Does anyone reckon the reason behind opt-out LLSC for IP28? As far as I understand
> there is no restriction on using LLSC after workaround being applied. If it's purely
> performance reason, I think I'll need to move kernel_uses_llsc logic to Kconfig as well.

commit 46dd40aa376c8158b6aa17510079caf5c3af6237
Author: Thomas Bogendoerfer <tsbogend@...ha.franken.de>
Date:   Wed Oct 7 12:17:04 2020 +0200

    MIPS: SGI-IP28: disable use of ll/sc in kernel
    
    SGI-IP28 systems only use broken R10k rev 2.5 CPUs, which could lock
    up, if ll/sc sequences are issued in certain order. Since those systems
    are all non-SMP, we can disable ll/sc usage in kernel.
    
    Signed-off-by: Thomas Bogendoerfer <tsbogend@...ha.franken.de>


Thomas.

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