linux-kernel - Re: [PATCH] driver core: Add a guard() definition for the device

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Date:   Thu, 14 Dec 2023 00:01:38 +0000
From:   "Verma, Vishal L" <vishal.l.verma@...el.com>
To:     "Williams, Dan J" <dan.j.williams@...el.com>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>
CC:     "peterz@...radead.org" <peterz@...radead.org>,
        "linux-cxl@...r.kernel.org" <linux-cxl@...r.kernel.org>,
        "nvdimm@...ts.linux.dev" <nvdimm@...ts.linux.dev>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "Weiny, Ira" <ira.weiny@...el.com>,
        "akpm@...ux-foundation.org" <akpm@...ux-foundation.org>
Subject: Re: [PATCH] driver core: Add a guard() definition for the
 device_lock()

On Wed, 2023-12-13 at 15:02 -0800, Dan Williams wrote:
> At present there are ~200 usages of device_lock() in the kernel. Some of
> those usages lead to "goto unlock;" patterns which have proven to be
> error prone. Define a "device" guard() definition to allow for those to

"Define a definition" sounds a bit awkward, perhaps  "Add a .."?

> be cleaned up and prevent new ones from appearing.
> 
> Link: http://lore.kernel.org/r/657897453dda8_269bd29492@dwillia2-mobl3.amr.corp.intel.com.notmuch
> Link: http://lore.kernel.org/r/6577b0c2a02df_a04c5294bb@dwillia2-xfh.jf.intel.com.notmuch
> Cc: Vishal Verma <vishal.l.verma@...el.com>
> Cc: Ira Weiny <ira.weiny@...el.com>
> Cc: Peter Zijlstra <peterz@...radead.org>
> Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> Cc: Andrew Morton <akpm@...ux-foundation.org>
> Signed-off-by: Dan Williams <dan.j.williams@...el.com>

Other than that, looks good,

Reviewed-by: Vishal Verma <vishal.l.verma@...el.com>

> ---
> Hi Greg,
> 
> I wonder if you might include this change in v6.7-rc to ease some patch
> sets alternately going through my tree and Andrew's tree. Those
> discussions are linked above. Alternately I can can just take it through
> my tree with your ack and the other use case can circle back to it in
> the v6.9 cycle.
> 
> I considered also defining a __free() helper similar to __free(mutex),
> but I think "__free(device)" would be a surprising name for something
> that drops a lock. Also, I like the syntax of guard(device) over
> something like guard(device_lock) since a 'struct device *' is the
> argument, not a lock type, but I'm open to your or Peter's thoughts on
> the naming.
> 
>  include/linux/device.h |    2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/include/linux/device.h b/include/linux/device.h
> index d7a72a8749ea..6c83294395ac 100644
> --- a/include/linux/device.h
> +++ b/include/linux/device.h
> @@ -1007,6 +1007,8 @@ static inline void device_unlock(struct device *dev)
>         mutex_unlock(&dev->mutex);
>  }
>  
> +DEFINE_GUARD(device, struct device *, device_lock(_T), device_unlock(_T))
> +
>  static inline void device_lock_assert(struct device *dev)
>  {
>         lockdep_assert_held(&dev->mutex);
>