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Message-ID: <YmM9n3QDDGhsZb5b@iweiny-desk3>
Date: Fri, 22 Apr 2022 16:43:27 -0700
From: Ira Weiny <ira.weiny@...el.com>
To: Dan Williams <dan.j.williams@...el.com>
Cc: linux-cxl@...r.kernel.org, Peter Zijlstra <peterz@...radead.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>,
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 1/8] cxl: Replace lockdep_mutex with local lock classes
On Thu, Apr 21, 2022 at 08:33:13AM -0700, Dan Williams wrote:
> In response to an attempt to expand dev->lockdep_mutex for device_lock()
> validation [1], Peter points out [2] that the lockdep API already has
> the ability to assign a dedicated lock class per subsystem device-type.
>
> Use lockdep_set_class() to override the default device_lock()
> '__lockdep_no_validate__' class for each CXL subsystem device-type. This
> enables lockdep to detect deadlocks and recursive locking within the
> device-driver core and the subsystem. The
> lockdep_set_class_and_subclass() API is used for port objects that
> recursively lock the 'cxl_port_key' class by hierarchical topology
> depth.
>
> Link: https://lore.kernel.org/r/164982968798.684294.15817853329823976469.stgit@dwillia2-desk3.amr.corp.intel.com [1]
> Link: https://lore.kernel.org/r/Ylf0dewci8myLvoW@hirez.programming.kicks-ass.net [2]
> Suggested-by: Peter Zijlstra <peterz@...radead.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>
Reviewed-by: Ira Weiny <ira.weiny@...el.com>
> ---
> drivers/cxl/core/memdev.c | 3 +++
> drivers/cxl/core/pmem.c | 6 ++++++
> drivers/cxl/core/port.c | 13 +++++++++----
> 3 files changed, 18 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/cxl/core/memdev.c b/drivers/cxl/core/memdev.c
> index 1f76b28f9826..f7cdcd33504a 100644
> --- a/drivers/cxl/core/memdev.c
> +++ b/drivers/cxl/core/memdev.c
> @@ -228,6 +228,8 @@ static void detach_memdev(struct work_struct *work)
> put_device(&cxlmd->dev);
> }
>
> +static struct lock_class_key cxl_memdev_key;
> +
> static struct cxl_memdev *cxl_memdev_alloc(struct cxl_dev_state *cxlds,
> const struct file_operations *fops)
> {
> @@ -247,6 +249,7 @@ static struct cxl_memdev *cxl_memdev_alloc(struct cxl_dev_state *cxlds,
>
> dev = &cxlmd->dev;
> device_initialize(dev);
> + lockdep_set_class(&dev->mutex, &cxl_memdev_key);
> dev->parent = cxlds->dev;
> dev->bus = &cxl_bus_type;
> dev->devt = MKDEV(cxl_mem_major, cxlmd->id);
> diff --git a/drivers/cxl/core/pmem.c b/drivers/cxl/core/pmem.c
> index 8de240c4d96b..e825e261278d 100644
> --- a/drivers/cxl/core/pmem.c
> +++ b/drivers/cxl/core/pmem.c
> @@ -80,6 +80,8 @@ struct cxl_nvdimm_bridge *cxl_find_nvdimm_bridge(struct cxl_nvdimm *cxl_nvd)
> }
> EXPORT_SYMBOL_NS_GPL(cxl_find_nvdimm_bridge, CXL);
>
> +static struct lock_class_key cxl_nvdimm_bridge_key;
> +
> static struct cxl_nvdimm_bridge *cxl_nvdimm_bridge_alloc(struct cxl_port *port)
> {
> struct cxl_nvdimm_bridge *cxl_nvb;
> @@ -99,6 +101,7 @@ static struct cxl_nvdimm_bridge *cxl_nvdimm_bridge_alloc(struct cxl_port *port)
> cxl_nvb->port = port;
> cxl_nvb->state = CXL_NVB_NEW;
> device_initialize(dev);
> + lockdep_set_class(&dev->mutex, &cxl_nvdimm_bridge_key);
> device_set_pm_not_required(dev);
> dev->parent = &port->dev;
> dev->bus = &cxl_bus_type;
> @@ -214,6 +217,8 @@ struct cxl_nvdimm *to_cxl_nvdimm(struct device *dev)
> }
> EXPORT_SYMBOL_NS_GPL(to_cxl_nvdimm, CXL);
>
> +static struct lock_class_key cxl_nvdimm_key;
> +
> static struct cxl_nvdimm *cxl_nvdimm_alloc(struct cxl_memdev *cxlmd)
> {
> struct cxl_nvdimm *cxl_nvd;
> @@ -226,6 +231,7 @@ static struct cxl_nvdimm *cxl_nvdimm_alloc(struct cxl_memdev *cxlmd)
> dev = &cxl_nvd->dev;
> cxl_nvd->cxlmd = cxlmd;
> device_initialize(dev);
> + lockdep_set_class(&dev->mutex, &cxl_nvdimm_key);
> device_set_pm_not_required(dev);
> dev->parent = &cxlmd->dev;
> dev->bus = &cxl_bus_type;
> diff --git a/drivers/cxl/core/port.c b/drivers/cxl/core/port.c
> index 2ab1ba4499b3..750aac95ed5f 100644
> --- a/drivers/cxl/core/port.c
> +++ b/drivers/cxl/core/port.c
> @@ -391,6 +391,8 @@ static int devm_cxl_link_uport(struct device *host, struct cxl_port *port)
> return devm_add_action_or_reset(host, cxl_unlink_uport, port);
> }
>
> +static struct lock_class_key cxl_port_key;
> +
> static struct cxl_port *cxl_port_alloc(struct device *uport,
> resource_size_t component_reg_phys,
> struct cxl_port *parent_port)
> @@ -415,9 +417,10 @@ static struct cxl_port *cxl_port_alloc(struct device *uport,
> * description.
> */
> dev = &port->dev;
> - if (parent_port)
> + if (parent_port) {
> dev->parent = &parent_port->dev;
> - else
> + port->depth = parent_port->depth + 1;
> + } else
> dev->parent = uport;
>
> port->uport = uport;
> @@ -427,6 +430,7 @@ static struct cxl_port *cxl_port_alloc(struct device *uport,
> INIT_LIST_HEAD(&port->endpoints);
>
> device_initialize(dev);
> + lockdep_set_class_and_subclass(&dev->mutex, &cxl_port_key, port->depth);
> device_set_pm_not_required(dev);
> dev->bus = &cxl_bus_type;
> dev->type = &cxl_port_type;
> @@ -457,8 +461,6 @@ struct cxl_port *devm_cxl_add_port(struct device *host, struct device *uport,
> if (IS_ERR(port))
> return port;
>
> - if (parent_port)
> - port->depth = parent_port->depth + 1;
> dev = &port->dev;
> if (is_cxl_memdev(uport))
> rc = dev_set_name(dev, "endpoint%d", port->id);
> @@ -1173,6 +1175,8 @@ static int decoder_populate_targets(struct cxl_decoder *cxld,
> return rc;
> }
>
> +static struct lock_class_key cxl_decoder_key;
> +
> /**
> * cxl_decoder_alloc - Allocate a new CXL decoder
> * @port: owning port of this decoder
> @@ -1214,6 +1218,7 @@ static struct cxl_decoder *cxl_decoder_alloc(struct cxl_port *port,
> seqlock_init(&cxld->target_lock);
> dev = &cxld->dev;
> device_initialize(dev);
> + lockdep_set_class(&dev->mutex, &cxl_decoder_key);
> device_set_pm_not_required(dev);
> dev->parent = &port->dev;
> dev->bus = &cxl_bus_type;
>
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