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

From: Catalin Marinas <catalin.marinas@arm.com>
To: "Russell King (Oracle)" <linux@armlinux.org.uk>
Cc: Marek Szyprowski <m.szyprowski@samsung.com>,
	Sudeep Holla <sudeep.holla@arm.com>,
	"Christoph Lameter (Ampere)" <cl@linux.com>,
	Mark Rutland <mark.rutland@arm.com>,
	"linux-pm@vger.kernel.org" <linux-pm@vger.kernel.org>,
	"Rafael J. Wysocki" <rafael@kernel.org>,
	Viresh Kumar <vireshk@kernel.org>, Will Deacon <will@kernel.org>,
	Jonathan.Cameron@huawei.com, Matteo.Carlini@arm.com,
	Valentin.Schneider@arm.com, akpm@linux-foundation.org,
	anshuman.khandual@arm.com, Eric Mackay <eric.mackay@oracle.com>,
	dave.kleikamp@oracle.com, linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org, linux-mm@kvack.org,
	robin.murphy@arm.com, vanshikonda@os.amperecomputing.com,
	yang@os.amperecomputing.com, Nishanth Menon <nm@ti.com>,
	Stephen Boyd <sboyd@kernel.org>
Subject: Re: [PATCH v3] ARM64: Dynamically allocate cpumasks and increase supported CPUs to 512
Date: Thu, 14 Mar 2024 08:39:46 +0000	[thread overview]
Message-ID: <ZfK30r8M6zx2aWU6@arm.com> (raw)
In-Reply-To: <ZfHevcKpcb6i1fn5@shell.armlinux.org.uk>

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