Re: [PATCH] xen/mm: Fix page_list_* helpers to evaluate all their arguments

From: Doug Goldstein <cardoe@cardoe.com>
To: Andrew Cooper <andrew.cooper3@citrix.com>,
	Xen-devel <xen-devel@lists.xen.org>
Cc: George Dunlap <george.dunlap@eu.citrix.com>,
	Tim Deegan <tim@xen.org>, Jan Beulich <JBeulich@suse.com>
Subject: Re: [PATCH] xen/mm: Fix page_list_* helpers to evaluate all their arguments
Date: Sat, 5 Mar 2016 17:42:54 -0600	[thread overview]
Message-ID: <56DB6EFE.1090801@cardoe.com> (raw)
In-Reply-To: <1457196754-6299-1-git-send-email-andrew.cooper3@citrix.com>

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On 3/5/16 10:52 AM, Andrew Cooper wrote:
> If an architecture does not provide a custom page_list_entry, default
> page_list_* helpers are provided, wrapping list_head as an underlying type for
> page_list_head.
> 
> The two declarations of the page_list_* helpers differ between defines and
> static inline functions, where the defines discard some of their parameters.
> 
> This causes a compilation failure if CONFIG_BIGMEM and debug=n in p2m-pod.c:
> 
>   p2m-pod.c: In function ‘p2m_pod_cache_add’:
>   p2m-pod.c:72:20: error: unused variable ‘d’ [-Werror=unused-variable]
>        struct domain *d = p2m->domain;
>                       ^
>   cc1: all warnings being treated as errors
> 
> because the use of d outside of the !NDEBUG section doesn't get evaluated as a
> parameter by page_list_del().
> 
> Fix this by turning all #defines into static inline functions, so all
> parameters are evaluated even if they are not used.
> 
> Doing this reveals that const-correctness of page_list_{next,prev}() is
> suspect, taking a const pointer and returning a non-const one.  It is left
> functioning as it did before, with an explicit typecast to remove constness.
> 
> While editing this area, correct the return type of page_list_empty from int
> to bool_t.
> 
> Reported-by: Doug Goldstein <cardoe@cardoe.com>
> Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>

Reviewed-by: Doug Goldstein <cardoe@cardoe.com>

I had planned on doing something similar but your commit message is much
better than what I would have come up with.

Not sure if people would like Identified-by: Travis CI but it actually
required a patch to be found.
http://lists.xen.org/archives/html/xen-devel/2016-03/msg00735.html which
is waiting to be merged.

-- 
Doug Goldstein

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