linux-kernel - Re: [PATCH] Documentation/sparse.txt: document context annotations for lock checking

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Message-ID: <20121018230948.GC10627@jtriplet-mobl1>
Date:	Thu, 18 Oct 2012 16:09:49 -0700
From:	Josh Triplett <josh@...htriplett.org>
To:	Ed Cashin <ecashin@...aid.com>
Cc:	akpm@...ux-foundation.org, rob@...dley.net,
	linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-sparse@...r.kernel.org, sam@...nborg.org, sparse@...isli.org,
	ak@...ux.intel.com
Subject: Re: [PATCH] Documentation/sparse.txt: document context annotations
 for lock checking

On Thu, Oct 18, 2012 at 07:27:26AM -0700, Ed Cashin wrote:
> The context feature of sparse is used with the Linux kernel
> sources to check for imbalanced uses of locks.  Document the
> annotations defined in include/linux/compiler.h that tell sparse
> what to expect when a lock is held on function entry, exit, or
> both.
> 
> Signed-off-by: Ed Cashin <ecashin@...aid.com>

Reviewed-by: Josh Triplett <josh@...htriplett.org>

>  Documentation/sparse.txt |   18 ++++++++++++++++++
>  1 files changed, 18 insertions(+), 0 deletions(-)
> 
> diff --git a/Documentation/sparse.txt b/Documentation/sparse.txt
> index 4909d41..eceab13 100644
> --- a/Documentation/sparse.txt
> +++ b/Documentation/sparse.txt
> @@ -49,6 +49,24 @@ be generated without __CHECK_ENDIAN__.
>  __bitwise - noisy stuff; in particular, __le*/__be* are that.  We really
>  don't want to drown in noise unless we'd explicitly asked for it.
>  
> +Using sparse for lock checking
> +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> +
> +The following macros are undefined for gcc and defined during a sparse
> +run to use the "context" tracking feature of sparse, applied to
> +locking.  These annotations tell sparse when a lock is held, with
> +regard to the annotated function's entry and exit.
> +
> +__must_hold - The specified lock is held on function entry and exit.
> +
> +__acquires - The specified lock is held on function exit, but not entry.
> +
> +__releases - The specified lock is held on function entry, but not exit.
> +
> +If the function enters and exits without the lock held, acquiring and
> +releasing the lock inside the function in a balanced way, no
> +annotation is needed.  The tree annotations above are for cases where
> +sparse would otherwise report a context imbalance.
>  
>  Getting sparse
>  ~~~~~~~~~~~~~~
> -- 
> 1.7.1
> 
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