[PATCH][2.6] first/next_cpu returns values > NR_CPUS

From: Zwane Mwaikambo (zwane_at_fsmlabs.com)
Date: 07/31/04

  • Next message: Zwane Mwaikambo: "[PATCH][2.6-mm] i386 Hotplug CPU" 
    Date:	Sat, 31 Jul 2004 16:52:18 -0400 (EDT)
To: Linux Kernel <linux-kernel@vger.kernel.org>

    The following caused some fireworks whilst merging i386 cpu hotplug.

    any_online_cpu(0x2) returns 32 on i386 if we're forced to continue past
    the only set bit due to the additional find_first_bit in the
    find_next_bit i386 implementation. Not wanting to change current
    behaviour in the bitops primitives and since the NR_CPUS thing is a
    cpumask issue, i've opted to fix next_cpu() and first_cpu() instead.

    Signed-off-by: Zwane Mwaikambo <zwane@fsmlabs.com>

    Index: linux-2.6.8-rc2-mm1-lch/include/linux/cpumask.h
    ===================================================================
    RCS file: /home/cvsroot/linux-2.6.8-rc2-mm1/include/linux/cpumask.h,v
    retrieving revision 1.1.1.1
    diff -u -p -B -r1.1.1.1 cpumask.h
    --- linux-2.6.8-rc2-mm1-lch/include/linux/cpumask.h 28 Jul 2004 14:35:22 -0000 1.1.1.1
    +++ linux-2.6.8-rc2-mm1-lch/include/linux/cpumask.h 31 Jul 2004 17:57:12 -0000
    @@ -207,13 +207,19 @@ static inline void __cpus_shift_left(cpu
     #define first_cpu(src) __first_cpu(&(src), NR_CPUS)
     static inline int __first_cpu(const cpumask_t *srcp, int nbits)
     {
    - return find_first_bit(srcp->bits, nbits);
    + int cpu = find_first_bit(srcp->bits, nbits);
    + if (cpu > NR_CPUS)
    + cpu = NR_CPUS;
    + return cpu;
     }

     #define next_cpu(n, src) __next_cpu((n), &(src), NR_CPUS)
     static inline int __next_cpu(int n, const cpumask_t *srcp, int nbits)
     {
    - return find_next_bit(srcp->bits, nbits, n+1);
    + int cpu = find_next_bit(srcp->bits, nbits, n+1);
    + if (cpu > NR_CPUS)
    + cpu = NR_CPUS;
    + return cpu;
     }

     #define cpumask_of_cpu(cpu) \
    -
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