Messages in this thread | | | Date | Mon, 9 Dec 2013 16:50:44 -0800 | From | Andrew Morton <> | Subject | Re: [PATCH] mm: nobootmem: avoid type warning about alignment value |
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On Mon, 25 Nov 2013 08:57:54 -0500 Santosh Shilimkar <santosh.shilimkar@ti.com> wrote:
> On Sunday 24 November 2013 10:14 AM, Sergei Shtylyov wrote: > > Hello. > > > > On 24-11-2013 3:28, Santosh Shilimkar wrote: > > > >> Building ARM with NO_BOOTMEM generates below warning. Using min_t > > > > Where is that below? :-) > > > Damn.. Posted a wrong version of the patch ;-( > Here is the one with warning message included. > > >From 571dfdf4cf8ac7dfd50bd9b7519717c42824f1c3 Mon Sep 17 00:00:00 2001 > From: Santosh Shilimkar <santosh.shilimkar@ti.com> > Date: Sat, 23 Nov 2013 18:16:50 -0500 > Subject: [PATCH] mm: nobootmem: avoid type warning about alignment value > > Building ARM with NO_BOOTMEM generates below warning. > > mm/nobootmem.c: In function _____free_pages_memory___: > mm/nobootmem.c:88:11: warning: comparison of distinct pointer types lacks a cast > > Using min_t to find the correct alignment avoids the warning. > > Cc: Tejun Heo <tj@kernel.org> > Cc: Andrew Morton <akpm@linux-foundation.org> > Signed-off-by: Santosh Shilimkar <santosh.shilimkar@ti.com> > --- > mm/nobootmem.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/mm/nobootmem.c b/mm/nobootmem.c > index 2c254d3..8954e43 100644 > --- a/mm/nobootmem.c > +++ b/mm/nobootmem.c > @@ -85,7 +85,7 @@ static void __init __free_pages_memory(unsigned long start, unsigned long end) > int order; > > while (start < end) { > - order = min(MAX_ORDER - 1UL, __ffs(start)); > + order = min_t(size_t, MAX_ORDER - 1UL, __ffs(start)); >
size_t makes no sense. Neither `order', `MAX_ORDER', 1UL nor __ffs() have that type.
min() warnings often indicate that the chosen types are inappropriate, and suppressing them with min_t() should be a last resort.
MAX_ORDER-1UL has type `unsigned long' (yes?) and __ffs() should return unsigned long (except arch/arc which decided to be different).
Why does it warn? What's the underlying reason?
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