1 files changed, 24 insertions, 39 deletions

diff --git a/include/linux/cpumask.h b/include/linux/cpumask.h
index 1b5c98e7fef7..96d0509fb8d8 100644
--- a/include/linux/cpumask.h
+++ b/include/linux/cpumask.h
@@ -62,15 +62,7 @@
  * int next_cpu_nr(cpu, mask)           Next cpu past 'cpu', or nr_cpu_ids
  *
  * cpumask_t cpumask_of_cpu(cpu)        Return cpumask with bit 'cpu' set
- *ifdef CONFIG_HAS_CPUMASK_OF_CPU
- * cpumask_of_cpu_ptr_declare(v)        Declares cpumask_t *v
- * cpumask_of_cpu_ptr_next(v, cpu)      Sets v = &cpumask_of_cpu_map[cpu]
- * cpumask_of_cpu_ptr(v, cpu)           Combines above two operations
- *else
- * cpumask_of_cpu_ptr_declare(v)        Declares cpumask_t _v and *v = &_v
- * cpumask_of_cpu_ptr_next(v, cpu)      Sets _v = cpumask_of_cpu(cpu)
- * cpumask_of_cpu_ptr(v, cpu)           Combines above two operations
- *endif
+ *                                      (can be used as an lvalue)
  * CPU_MASK_ALL                         Initializer - all bits set
  * CPU_MASK_NONE                        Initializer - no bits set
  * unsigned long *cpus_addr(mask)       Array of unsigned long's in mask
@@ -273,37 +265,30 @@ static inline void __cpus_shift_left(cpumask_t *dstp,
         bitmap_shift_left(dstp->bits, srcp->bits, n, nbits);
 }
 
+/*
+ * Special-case data structure for "single bit set only" constant CPU masks.
+ *
+ * We pre-generate all the 64 (or 32) possible bit positions, with enough
+ * padding to the left and the right, and return the constant pointer
+ * appropriately offset.
+ */
+extern const unsigned long
+        cpu_bit_bitmap[BITS_PER_LONG+1][BITS_TO_LONGS(NR_CPUS)];
+
+static inline const cpumask_t *get_cpu_mask(unsigned int cpu)
+{
+        const unsigned long *p = cpu_bit_bitmap[1 + cpu % BITS_PER_LONG];
+        p -= cpu / BITS_PER_LONG;
+        return (const cpumask_t *)p;
+}
+
+/*
+ * In cases where we take the address of the cpumask immediately,
+ * gcc optimizes it out (it's a constant) and there's no huge stack
+ * variable created:
+ */
+#define cpumask_of_cpu(cpu) ({ *get_cpu_mask(cpu); })
 
-#ifdef CONFIG_HAVE_CPUMASK_OF_CPU_MAP
-extern cpumask_t *cpumask_of_cpu_map;
-#define cpumask_of_cpu(cpu)     (cpumask_of_cpu_map[cpu])
-#define cpumask_of_cpu_ptr(v, cpu)                                      \
-                const cpumask_t *v = &cpumask_of_cpu(cpu)
-#define cpumask_of_cpu_ptr_declare(v)                                   \
-                const cpumask_t *v
-#define cpumask_of_cpu_ptr_next(v, cpu)                                 \
-                                        v = &cpumask_of_cpu(cpu)
-#else
-#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;                                                              \
-})
-#define cpumask_of_cpu_ptr(v, cpu)                                      \
-                cpumask_t _##v = cpumask_of_cpu(cpu);                   \
-                const cpumask_t *v = &_##v
-#define cpumask_of_cpu_ptr_declare(v)                                   \
-                cpumask_t _##v;                                         \
-                const cpumask_t *v = &_##v
-#define cpumask_of_cpu_ptr_next(v, cpu)                                 \
-                                        _##v = cpumask_of_cpu(cpu)
-#endif
 
 #define CPU_MASK_LAST_WORD BITMAP_LAST_WORD_MASK(NR_CPUS)