linux-kernel - Re: [PATCH v2 01/28] coresight: Change device mode to atomic type

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Message-ID: <20250804082226.GH143191@e132581.arm.com>
Date: Mon, 4 Aug 2025 09:22:26 +0100
From: Leo Yan <leo.yan@....com>
To: Anshuman Khandual <anshuman.khandual@....com>
Cc: Suzuki K Poulose <suzuki.poulose@....com>,
	Mike Leach <mike.leach@...aro.org>,
	James Clark <james.clark@...aro.org>,
	Levi Yun <yeoreum.yun@....com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
	Yabin Cui <yabinc@...gle.com>, Keita Morisaki <keyz@...gle.com>,
	Yuanfang Zhang <quic_yuanfang@...cinc.com>,
	coresight@...ts.linaro.org, linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 01/28] coresight: Change device mode to atomic type

On Tue, Jul 15, 2025 at 12:23:22PM +0530, Anshuman Khandual wrote:
> On 01/07/25 8:23 PM, Leo Yan wrote:
> > The device mode is defined as local type. This type cannot promise
> > SMP-safe access.
> > 
> > Change to atomic type and impose relax ordering, which ensures the
> > SMP-safe synchronisation and the ordering between the mode setting and
> > relevant operations.
> 
> 
> But have we really faced such problems on real systems due to local_t
> or this is just an improvement ?

This is an improvement based on reading code. The reason is the
variable is accessed by mutliple CPUs but not per-CPU access.

Thanks,
Leo