linux-kernel - Re: [PATCH v4 5/7] cxl/region: Introduce SOFT RESERVED resource removal on region teardown

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Message-ID: <20250610103704.000023c4@huawei.com>
Date: Tue, 10 Jun 2025 10:37:04 +0100
From: Jonathan Cameron <Jonathan.Cameron@...wei.com>
To: "Koralahalli Channabasappa, Smita"
	<Smita.KoralahalliChannabasappa@....com>
CC: <linux-cxl@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
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	<PradeepVineshReddy.Kodamati@....com>, Zhijian Li <lizhijian@...itsu.com>
Subject: Re: [PATCH v4 5/7] cxl/region: Introduce SOFT RESERVED resource
 removal on region teardown

Hi Smita,

> >> +/*
> >> + * normalize_resource
> >> + *
> >> + * The walk_iomem_res_desc() returns a copy of a resource, not a reference
> >> + * to the actual resource in the iomem_resource tree. As a result,
> >> + * __release_resource() which relies on pointer equality will fail.  
> > 
> > Probably want some statement on why nothing can race with this give
> > the resource_lock is not being held.  
> 
> Hmm, probably you are right that normalize_resource() is accessing the 
> resource tree without holding resource_lock, which could lead to races.
> 
> I will update the function to take a read_lock(&resource_lock) before 
> walking res->parent->child..
> 
> Let me know if you'd prefer this locking be handled before calling 
> normalize_resource() instead..
I don't mind either way - see what looks better to you.