linux-kernel - Re: [PATCH 02/11] cxl/core: Refactor a cxl_lock_class() out of cxl_nested

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Date:   Wed, 9 Mar 2022 18:18:43 +0000
From:   Jonathan Cameron <Jonathan.Cameron@...wei.com>
To:     Dan Williams <dan.j.williams@...el.com>
CC:     <gregkh@...uxfoundation.org>, <rafael.j.wysocki@...el.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>,
        <linux-kernel@...r.kernel.org>, <linux-cxl@...r.kernel.org>,
        <nvdimm@...ts.linux.dev>
Subject: Re: [PATCH 02/11] cxl/core: Refactor a cxl_lock_class() out of
 cxl_nested_lock()

On Mon, 28 Feb 2022 18:49:00 -0800
Dan Williams <dan.j.williams@...el.com> wrote:

> In preparation for upleveling device_lock() lockdep annotation support into
> the core, provide a helper to retrieve the lock class. This lock_class
> will be used with device_set_lock_class() to idenify the CXL nested

idenify?

> locking rules.
> 
> 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>
> Signed-off-by: Dan Williams <dan.j.williams@...el.com>

Otherwise looks fine to me.

Reviewed-by: Jonathan Cameron <Jonathan.Cameron@...wei.com>

> ---
>  drivers/cxl/cxl.h |   19 +++++++++++--------
>  1 file changed, 11 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/cxl/cxl.h b/drivers/cxl/cxl.h
> index 5486fb6aebd4..ca8a61a623b7 100644
> --- a/drivers/cxl/cxl.h
> +++ b/drivers/cxl/cxl.h
> @@ -509,13 +509,12 @@ enum cxl_lock_class {
>  	 */
>  };
>  
> -static inline void cxl_nested_lock(struct device *dev)
> +static inline int cxl_lock_class(struct device *dev)
>  {
>  	if (is_cxl_port(dev)) {
>  		struct cxl_port *port = to_cxl_port(dev);
>  
> -		mutex_lock_nested(&dev->lockdep_mutex,
> -				  CXL_PORT_LOCK + port->depth);
> +		return CXL_PORT_LOCK + port->depth;
>  	} else if (is_cxl_decoder(dev)) {
>  		struct cxl_port *port = to_cxl_port(dev->parent);
>  
> @@ -523,14 +522,18 @@ static inline void cxl_nested_lock(struct device *dev)
>  		 * A decoder is the immediate child of a port, so set
>  		 * its lock class equal to other child device siblings.
>  		 */
> -		mutex_lock_nested(&dev->lockdep_mutex,
> -				  CXL_PORT_LOCK + port->depth + 1);
> +		return CXL_PORT_LOCK + port->depth + 1;
>  	} else if (is_cxl_nvdimm_bridge(dev))
> -		mutex_lock_nested(&dev->lockdep_mutex, CXL_NVDIMM_BRIDGE_LOCK);
> +		return CXL_NVDIMM_BRIDGE_LOCK;
>  	else if (is_cxl_nvdimm(dev))
> -		mutex_lock_nested(&dev->lockdep_mutex, CXL_NVDIMM_LOCK);
> +		return CXL_NVDIMM_LOCK;
>  	else
> -		mutex_lock_nested(&dev->lockdep_mutex, CXL_ANON_LOCK);
> +		return CXL_ANON_LOCK;
> +}
> +
> +static inline void cxl_nested_lock(struct device *dev)
> +{
> +	mutex_lock_nested(&dev->lockdep_mutex, cxl_lock_class(dev));
>  }
>  
>  static inline void cxl_nested_unlock(struct device *dev)
>