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    cpumask: Replace cpumask_of_cpu with cpumask_of_cpu_ptr · 65c01184
    Mike Travis 提交于
      * This patch 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.
    
        In general terms, if there is a cpumask_of_cpu_map[] then a pointer to
        the cpumask_of_cpu_map[cpu] entry is used.  The cpumask_of_cpu_map
        is provided when there is a large NR_CPUS count, reducing
        greatly the amount of code generated and stack space used for
        cpumask_of_cpu().  The pointer to the cpumask_t value is needed for
        calling set_cpus_allowed_ptr() to reduce the amount of stack space
        needed to pass the cpumask_t value.
    
        If there isn't a cpumask_of_cpu_map[], then a temporary variable is
        declared and filled in with value from cpumask_of_cpu(cpu) as well as
        a pointer variable pointing to this temporary variable.  Afterwards,
        the pointer is used to reference the cpumask value.  The compiler
        will optimize out the extra dereference through the pointer as well
        as the stack space used for the pointer, resulting in identical code.
    
        A good example of the orthogonal usages is in net/sunrpc/svc.c:
    
    	case SVC_POOL_PERCPU:
    	{
    		unsigned int cpu = m->pool_to[pidx];
    		cpumask_of_cpu_ptr(cpumask, cpu);
    
    		*oldmask = current->cpus_allowed;
    		set_cpus_allowed_ptr(current, cpumask);
    		return 1;
    	}
    	case SVC_POOL_PERNODE:
    	{
    		unsigned int node = m->pool_to[pidx];
    		node_to_cpumask_ptr(nodecpumask, node);
    
    		*oldmask = current->cpus_allowed;
    		set_cpus_allowed_ptr(current, nodecpumask);
    		return 1;
    	}
    Signed-off-by: NMike Travis <travis@sgi.com>
    Signed-off-by: NIngo Molnar <mingo@elte.hu>
    65c01184
processor_throttling.c 32.1 KB