From: Dan Williams <dan.j.williams@intel.com>
To: Ira Weiny <ira.weiny@intel.com>
Cc: linux-cxl@vger.kernel.org, Peter Zijlstra <peterz@infradead.org>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
"Rafael J. Wysocki" <rafael@kernel.org>,
Ingo Molnar <mingo@redhat.com>, Will Deacon <will@kernel.org>,
Waiman Long <longman@redhat.com>,
Boqun Feng <boqun.feng@gmail.com>,
Alison Schofield <alison.schofield@intel.com>,
Vishal Verma <vishal.l.verma@intel.com>,
Ben Widawsky <ben.widawsky@intel.com>,
Jonathan Cameron <Jonathan.Cameron@huawei.com>,
Linux NVDIMM <nvdimm@lists.linux.dev>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v3 2/8] cxl/acpi: Add root device lockdep validation
Date: Fri, 22 Apr 2022 17:08:43 -0700 [thread overview]
Message-ID: <CAPcyv4jtNgfjWLyu6MtBAjwUiqe2qEBW802AzZZeg2gZ_wU9AQ@mail.gmail.com> (raw)
In-Reply-To: <YmNBJBTxUCvDHMbw@iweiny-desk3>
On Fri, Apr 22, 2022 at 4:58 PM Ira Weiny <ira.weiny@intel.com> wrote:
>
> 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.
>
> This final sentence gave me pause because it implied that the device lock class
> was set to something other than no validate. But I don't see that anywhere in
> the acpi code. So given that it looks to me like ACPI is just using the
> default no validate class...
Oh, good observation. *If* ACPI had set a custom lock class then
cxl_acpi would need to be careful to restore that ACPI-specific class
and not reset it to "no validate" on exit, or skip setting its own
custom class. However, I think for generic buses like ACPI that feed
devices into other subsystems it likely has little reason to set its
own class. For safety, since device_lock_set_class() is general
purpose, I'll have it emit a debug message and fail if the class is
not "no validate" on entry.
Thanks Ira!
next prev parent reply other threads:[~2022-04-23 0:08 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-04-21 15:33 [PATCH v3 0/8] device-core: Enable device_lock() lockdep validation Dan Williams
2022-04-21 15:33 ` [PATCH v3 1/8] cxl: Replace lockdep_mutex with local lock classes Dan Williams
2022-04-22 23:43 ` Ira Weiny
2022-04-21 15:33 ` [PATCH v3 2/8] cxl/acpi: Add root device lockdep validation Dan Williams
2022-04-21 16:10 ` Greg Kroah-Hartman
2022-04-22 23:58 ` Ira Weiny
2022-04-23 0:08 ` Dan Williams [this message]
2022-04-23 17:27 ` Dan Williams
2022-04-25 10:33 ` Peter Zijlstra
2022-04-25 16:05 ` Dan Williams
2022-04-25 18:57 ` Dan Williams
2022-04-23 21:05 ` [PATCH v4 " Dan Williams
2022-04-26 4:23 ` [PATCH v5 " Dan Williams
2022-04-26 19:22 ` [PATCH v6 " Dan Williams
2022-04-21 15:33 ` [PATCH v3 3/8] cxl: Drop cxl_device_lock() Dan Williams
2022-04-23 0:07 ` Ira Weiny
2022-04-21 15:33 ` [PATCH v3 4/8] nvdimm: Replace lockdep_mutex with local lock classes Dan Williams
2022-04-23 0:19 ` Ira Weiny
2022-04-21 15:33 ` [PATCH v3 5/8] ACPI: NFIT: Drop nfit_device_lock() Dan Williams
2022-04-23 0:21 ` Ira Weiny
2022-04-21 15:33 ` [PATCH v3 6/8] nvdimm: Drop nd_device_lock() Dan Williams
2022-04-23 0:24 ` Ira Weiny
2022-04-21 15:33 ` [PATCH v3 7/8] device-core: Kill the lockdep_mutex Dan Williams
2022-04-21 16:09 ` Greg Kroah-Hartman
2022-04-23 0:25 ` Ira Weiny
2022-04-21 15:33 ` [PATCH v3 8/8] nvdimm: Fix firmware activation deadlock scenarios Dan Williams
2022-04-23 4:28 ` Ira Weiny
2022-04-23 17:29 ` Dan Williams
2022-04-23 21:22 ` [PATCH v4 " Dan Williams
2022-04-24 23:30 ` Ira Weiny
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