Re: [PATCH] nodemask_t x86_64 changes [5/7]

From: Keith Owens (kaos_at_sgi.com)
Date: 03/29/04

  • Next message: Paul Jackson: "Re: [PATCH] nodemask_t x86_64 changes [5/7]" 
    To: Paul Jackson <pj@sgi.com>
Date:	Mon, 29 Mar 2004 15:08:46 +1000

    On Thu, 25 Mar 2004 23:14:12 -0800,
    Paul Jackson <pj@sgi.com> wrote:
    >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

    I only did one case, to concentrate on the value for the last word. A
    full implementation has to cater for NR_CPUS < BITS_PER_LONG as well.

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

    For big endian, ~0UL << NR_CPUS_UNDEF is right. For little endian, it
    depends on how you represent an incomplete bit map. Is it represented
    as a pure bit string, i.e. as if the arch were big endian? Or is it
    represented as a mapping onto the bytes of the underlying long?

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