linux-kernel - Re: [PATCH v3 2/8] cxl/acpi: Add root device lockdep validation

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Message-ID: <YmGB5DMVAaIq3HYl@kroah.com>
Date:   Thu, 21 Apr 2022 18:10:12 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Dan Williams <dan.j.williams@...el.com>
Cc:     linux-cxl@...r.kernel.org, Peter Zijlstra <peterz@...radead.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Ingo Molnar <mingo@...hat.com>, Will Deacon <will@...nel.org>,
        Waiman Long <longman@...hat.com>,
        Boqun Feng <boqun.feng@...il.com>,
        Alison Schofield <alison.schofield@...el.com>,
        Vishal Verma <vishal.l.verma@...el.com>,
        Ira Weiny <ira.weiny@...el.com>,
        Ben Widawsky <ben.widawsky@...el.com>,
        Jonathan Cameron <Jonathan.Cameron@...wei.com>,
        nvdimm@...ts.linux.dev, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 2/8] cxl/acpi: Add root device lockdep validation

On Thu, Apr 21, 2022 at 08:33:18AM -0700, Dan Williams wrote:
> The CXL "root" device, ACPI0017, is an attach point for coordinating
> platform level CXL resources and is the parent device for a CXL port
> topology tree. As such it has distinct locking rules relative to other
> CXL subsystem objects, but because it is an ACPI device the lock class
> is established well before it is given to the cxl_acpi driver.
> 
> However, the lockdep API does support changing the lock class "live" for
> situations like this. Add a device_lock_set_class() helper that a driver
> can use in ->probe() to set a custom lock class, and
> device_lock_reset_class() to return to the default "no validate" class
> before the custom lock class key goes out of scope after ->remove().
> 
> Note the helpers are all macros to support dead code elimination in the
> CONFIG_PROVE_LOCKING=n case.
> 
> Suggested-by: Peter Zijlstra <peterz@...radead.org>
> Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> Cc: "Rafael J. Wysocki" <rafael@...nel.org>
> Cc: Ingo Molnar <mingo@...hat.com>
> Cc: Will Deacon <will@...nel.org>
> Cc: Waiman Long <longman@...hat.com>
> Cc: Boqun Feng <boqun.feng@...il.com>
> Cc: Alison Schofield <alison.schofield@...el.com>
> Cc: Vishal Verma <vishal.l.verma@...el.com>
> Cc: Ira Weiny <ira.weiny@...el.com>
> Cc: Ben Widawsky <ben.widawsky@...el.com>
> Cc: Jonathan Cameron <Jonathan.Cameron@...wei.com>
> Signed-off-by: Dan Williams <dan.j.williams@...el.com>
> ---
>  drivers/cxl/acpi.c     |   15 +++++++++++++++
>  include/linux/device.h |   25 +++++++++++++++++++++++++
>  2 files changed, 40 insertions(+)

Much simpler, great work.

Reviewed-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>