x86: convert cpumask_of_cpu macro to allocated array

  * Here is a simple patch to use an allocated array of cpumasks to
    represent cpumask_of_cpu() instead of constructing one on the stack.
    It's based on the Kconfig option "HAVE_CPUMASK_OF_CPU_MAP" which is
    currently only set for x86_64 SMP.  Otherwise the the existing
    cpumask_of_cpu() is used but has been changed to produce an lvalue
    so a pointer to it can be used.

Cc: H. Peter Anvin <hpa@zytor.com>
Signed-off-by: Christoph Lameter <clameter@sgi.com>
Signed-off-by: Mike Travis <travis@sgi.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 9 insertions, 3 deletions

diff --git a/include/linux/cpumask.h b/include/linux/cpumask.h
index 629102feaa66..259c8051155d 100644
--- a/include/linux/cpumask.h
+++ b/include/linux/cpumask.h
@@ -222,8 +222,13 @@ int __next_cpu(int n, const cpumask_t *srcp);
 #define next_cpu(n, src)        ({ (void)(src); 1; })
 #endif
 
+#ifdef CONFIG_HAVE_CPUMASK_OF_CPU_MAP
+extern cpumask_t *cpumask_of_cpu_map;
+#define cpumask_of_cpu(cpu)    (cpumask_of_cpu_map[cpu])
+
+#else
 #define cpumask_of_cpu(cpu)                                             \
-({                                                                      \
+(*({                                                                    \
         typeof(_unused_cpumask_arg_) m;                                 \
         if (sizeof(m) == sizeof(unsigned long)) {                       \
                 m.bits[0] = 1UL<<(cpu);                                 \
@@ -231,8 +236,9 @@ int __next_cpu(int n, const cpumask_t *srcp);
                 cpus_clear(m);                                          \
                 cpu_set((cpu), m);                                      \
         }                                                               \
-        m;                                                              \
-})
+        &m;                                                             \
+}))
+#endif
 
 #define CPU_MASK_LAST_WORD BITMAP_LAST_WORD_MASK(NR_CPUS)