cpumask: Replace cpumask_of_cpu with cpumask_of_cpu_ptr

  * 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: Mike Travis <travis@sgi.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 7 insertions, 3 deletions

diff --git a/arch/x86/kernel/cpu/cpufreq/acpi-cpufreq.c b/arch/x86/kernel/cpu/cpufreq/acpi-cpufreq.c
index dd097b835839..ff2fff56f0a8 100644
--- a/arch/x86/kernel/cpu/cpufreq/acpi-cpufreq.c
+++ b/arch/x86/kernel/cpu/cpufreq/acpi-cpufreq.c
@@ -200,10 +200,12 @@ static void drv_read(struct drv_cmd *cmd)
 static void drv_write(struct drv_cmd *cmd)
 {
         cpumask_t saved_mask = current->cpus_allowed;
+        cpumask_of_cpu_ptr_declare(cpu_mask);
         unsigned int i;
 
         for_each_cpu_mask_nr(i, cmd->mask) {
-                set_cpus_allowed_ptr(current, &cpumask_of_cpu(i));
+                cpumask_of_cpu_ptr_next(cpu_mask, i);
+                set_cpus_allowed_ptr(current, cpu_mask);
                 do_drv_write(cmd);
         }
 
@@ -267,11 +269,12 @@ static unsigned int get_measured_perf(unsigned int cpu)
         } aperf_cur, mperf_cur;
 
         cpumask_t saved_mask;
+        cpumask_of_cpu_ptr(cpu_mask, cpu);
         unsigned int perf_percent;
         unsigned int retval;
 
         saved_mask = current->cpus_allowed;
-        set_cpus_allowed_ptr(current, &cpumask_of_cpu(cpu));
+        set_cpus_allowed_ptr(current, cpu_mask);
         if (get_cpu() != cpu) {
                 /* We were not able to run on requested processor */
                 put_cpu();
@@ -337,6 +340,7 @@ static unsigned int get_measured_perf(unsigned int cpu)
 
 static unsigned int get_cur_freq_on_cpu(unsigned int cpu)
 {
+        cpumask_of_cpu_ptr(cpu_mask, cpu);
         struct acpi_cpufreq_data *data = per_cpu(drv_data, cpu);
         unsigned int freq;
         unsigned int cached_freq;
@@ -349,7 +353,7 @@ static unsigned int get_cur_freq_on_cpu(unsigned int cpu)
         }
 
         cached_freq = data->freq_table[data->acpi_data->state].frequency;
-        freq = extract_freq(get_cur_val(&cpumask_of_cpu(cpu)), data);
+        freq = extract_freq(get_cur_val(cpu_mask), data);
         if (freq != cached_freq) {
                 /*
                  * The dreaded BIOS frequency change behind our back.