linux-kernel - Re: [PATCH v3] ARM64: Dynamically allocate cpumasks and increase supported CPUs to 512

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Message-ID: <ZfK30r8M6zx2aWU6@arm.com>
Date: Thu, 14 Mar 2024 08:39:46 +0000
From: Catalin Marinas <catalin.marinas@....com>
To: "Russell King (Oracle)" <linux@...linux.org.uk>
Cc: Marek Szyprowski <m.szyprowski@...sung.com>,
	Sudeep Holla <sudeep.holla@....com>,
	"Christoph Lameter (Ampere)" <cl@...ux.com>,
	Mark Rutland <mark.rutland@....com>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
	"Rafael J. Wysocki" <rafael@...nel.org>,
	Viresh Kumar <vireshk@...nel.org>, Will Deacon <will@...nel.org>,
	Jonathan.Cameron@...wei.com, Matteo.Carlini@....com,
	Valentin.Schneider@....com, akpm@...ux-foundation.org,
	anshuman.khandual@....com, Eric Mackay <eric.mackay@...cle.com>,
	dave.kleikamp@...cle.com, linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	robin.murphy@....com, vanshikonda@...amperecomputing.com,
	yang@...amperecomputing.com, Nishanth Menon <nm@...com>,
	Stephen Boyd <sboyd@...nel.org>
Subject: Re: [PATCH v3] ARM64: Dynamically allocate cpumasks and increase
 supported CPUs to 512

On Wed, Mar 13, 2024 at 05:13:33PM +0000, Russell King wrote:
> So, I wonder whether what you're seeing is a latent bug which is
> being tickled by the presence of the CPU masks being off-stack
> changing the kernel timing.
> 
> I would suggest the printk debug approach may help here to see when
> the OPPs are begun to be parsed, when they're created etc and their
> timing relationship to being used. Given the suspicion, it's possible
> that the mere addition of printk() may "fix" the problem, which again
> would be another semi-useful data point.

It might be an init order problem. Passing "initcall_debug" on the
cmdline might help a bit.

It would also be useful in dev_pm_opp_set_config(), in the WARN_ON
block, to print opp_table->opp_list.next to get an idea whether it looks
like a valid pointer or memory corruption.

-- 
Catalin