[PATCH 14/35] cpumask: make nr_cpu_ids valid in all configurations.

[Mike Travis]

nr_cpu_ids is the (badly named) runtime limit on possible CPU numbers;
ie. the variable version of NR_CPUS.

This makes is valid in all configs, including UP.

From: Rusty Russell <rusty@xxxxxxxxxxxxxxx>
Signed-off-by: Rusty Russell <rusty@xxxxxxxxxxxxxxx>
Signed-off-by: Mike Travis <travis@xxxxxxx>
---
 include/linux/cpumask.h |   10 ++++++++--
 init/main.c             |    7 +++++++
 2 files changed, 15 insertions(+), 2 deletions(-)

--- test-compile.orig/include/linux/cpumask.h
+++ test-compile/include/linux/cpumask.h
@@ -195,6 +195,14 @@ extern cpumask_t _unused_cpumask_arg_;
 #define cpus_addr(src) ((src).bits)
 /* End deprecated region. */
 
+#if NR_CPUS <= BITS_PER_LONG
+/* Constant is usually more efficient than a variable for small NR_CPUS */
+#define nr_cpu_ids NR_CPUS
+#else
+/* Starts at NR_CPUS until we know better. */
+extern int nr_cpu_ids;
+#endif /* NR_CPUS > BITS_PER_LONG */
+
 static inline void cpumask_set_cpu(int cpu, volatile struct cpumask *dstp)
 {
 	set_bit(cpu, dstp->bits);
@@ -434,7 +442,6 @@ extern cpumask_t cpu_mask_all;
 
 #if NR_CPUS == 1
 
-#define nr_cpu_ids			1
 #define first_cpu(src)			({ (void)(src); 0; })
 #define next_cpu(n, src)		({ (void)(src); 1; })
 #define cpumask_next_and(n, srcp, andp)	({ (void)(srcp), (void)(andp); 1; })
@@ -447,7 +454,6 @@ extern cpumask_t cpu_mask_all;
 
 #else /* NR_CPUS > 1 */
 
-extern int nr_cpu_ids;
 int __first_cpu(const cpumask_t *srcp);
 int __next_cpu(int n, const cpumask_t *srcp);
 int cpumask_next_and(int n, const cpumask_t *srcp, const cpumask_t *andp);
--- test-compile.orig/init/main.c
+++ test-compile/init/main.c
@@ -373,6 +373,8 @@ EXPORT_SYMBOL(cpu_mask_all);
 #endif
 
 /* Setup number of possible processor ids */
+/* nr_cpu_ids is a real variable for large NR_CPUS. */
+#ifndef nr_cpu_ids
 int nr_cpu_ids __read_mostly = NR_CPUS;
 EXPORT_SYMBOL(nr_cpu_ids);
 
@@ -386,6 +388,11 @@ void __init setup_nr_cpu_ids(void)
 
 	nr_cpu_ids = highest_cpu + 1;
 }
+#else
+void __init setup_nr_cpu_ids(void)
+{
+}
+#endif /* ... nr_cpu_ids is a constant. */
 
 #ifndef CONFIG_HAVE_SETUP_PER_CPU_AREA
 unsigned long __per_cpu_offset[NR_CPUS] __read_mostly;

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