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    Subject[PATCH 0/8] cpumask: Replace/optimize cpumask_of_cpu & cpumask_t operations

    > From Rusty Russell <rusty@rustcorp.com.au>:
    >
    > Hi Christoph/Mike,
    >
    > Looked at cpumask_of_cpu as introduced in
    > 9f0e8d0400d925c3acd5f4e01dbeb736e4011882 (x86: convert cpumask_of_cpu
    > macro to allocated array), and I don't think it's safe:
    >
    > #define cpumask_of_cpu(cpu) \
    > (*({ \
    > typeof(_unused_cpumask_arg_) m; \
    > if (sizeof(m) == sizeof(unsigned long)) { \
    > m.bits[0] = 1UL<<(cpu); \
    > } else { \
    > cpus_clear(m); \
    > cpu_set((cpu), m); \
    > } \
    > &m; \
    > }))
    >
    > Referring to &m once out of scope is invalid, and I can't find any
    > evidence that it's legal here. In particular, the change
    > b53e921ba1cff8453dc9a87a84052fa12d5b30bd (generic: reduce stack pressure
    > in sched_affinity) which passes &m to other functions seems highly risky.

    * Patch 1 replaces the dangerous lvalue version of cpumask_of_cpu
    with new cpumask_of_cpu_ptr macros. These are patterned after the
    node_to_cpumask_ptr macros.

    * Patches 2..6 optimizes various places where a pointer to the cpumask_of_cpu
    value will result in reducing stack pressure.

    * Patch 7 provides a generic set of CPUMASK_ALLOC macros patterned after
    the SCHED_CPUMASK_ALLOC macros. This is used where multiple cpumask_t
    variables are declared on the stack to reduce the amount of stack space
    required.

    * Patch 8 uses the CPUMASK_ALLOC macros in the centrino_target() function.

    Based on linux-2.6.tip/master at the following commit:

    commit 0a91813e16ebd5c2d9b5c2acd5b7c91742112c4f
    Merge: 9a635fa... 724dce0...
    Author: Ingo Molnar <mingo@elte.hu>
    Date: Tue Jul 15 14:55:17 2008 +0200


    Signed-off-by: Mike Travis <travis@sgi.com>
    Cc: Tigran Aivazian <tigran@aivazian.fsnet.co.uk>
    Cc: Greg Banks <gnb@sgi.com>
    Cc: Len Brown <len.brown@intel.com>
    Cc: Adrian Bunk <bunk@kernel.org>
    Cc: Thomas Gleixner <tglx@linutronix.de>
    Cc: Paul Jackson <pj@sgi.com>
    Cc: Dave Jones <davej@codemonkey.org.uk>
    Cc: Dean Nelson <dcn@sgi.com>
    Cc: Venki Pallipadi <venkatesh.pallipadi@intel.com>
    Cc: Robert Richter <robert.richter@amd.com>
    Cc: Eric W. Biederman <ebiederm@xmission.com>
    ---

    --


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