Date: Thu, 25 Mar 2004 23:14:12 -0800
From: Paul Jackson <pj@sgi.com>
To: Keith Owens <kaos@sgi.com>
Cc: wli@holomorphy.com, colpatch@us.ibm.com, linux-kernel@vger.kernel.org,
       mbligh@aracnet.com, akpm@osdl.org, haveblue@us.ibm.com
Subject: Re: [PATCH] nodemask_t x86_64 changes [5/7]
Message-Id: <20040325231412.2a3d1c15.pj@sgi.com>
In-Reply-To: <6562.1080277594@kao2.melbourne.sgi.com>
References: <20040323201101.3427494c.pj@sgi.com>
	<6562.1080277594@kao2.melbourne.sgi.com>
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> CPU_MASK_ALL ...

Yup - now you tell me ... ;).

I just got done figuring it out in a slightly variant way ... ('nbits'
is NR_CPUS or similar):

#define MASK_LAST_WORD(nbits)                                           \
(                                                                       \
        ((nbits) % BITS_PER_LONG) ?                                     \
                (1<<((nbits) % BITS_PER_LONG))-1 : ~0UL                 \
)

#define MASK_ALL(nbits)                                                 \
{ {                                                                     \
        [0 ... BITS_TO_LONGS(nbits)-1] = ~0UL,                          \
        [BITS_TO_LONGS(nbits)-1] = MASK_LAST_WORD(nbits)                \
} }

This way overwrites the last word of the mask, first putting ~0UL
in all words, then however many bits are needed in the last word.

Does your way work if NR_CPUS is less than BITS_PER_LONG?
Won't gcc complain upon seeing something like, for say
NR_CPUS = 4 on a 32 bit system:

   { [ 0 ... -1 ] = ~0UL, ~0UL << 28 }

with the errors and warnings:

  error: empty index range in initializer
  warning: excess elements in struct initializer

and shouldn't the last word be inverted: ~(~0UL << NR_CPUS_UNDEF) ?

-- 
                          I won't rest till it's the best ...
                          Programmer, Linux Scalability
                          Paul Jackson <pj@sgi.com> 1.650.933.1373
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