[PATCH 4/7] smp,cpumask: introduce on_each_cpu_cond_mask

[Rik van Riel]

Introduce a variant of on_each_cpu_cond that iterates only over the
CPUs in a cpumask, in order to avoid making callbacks for every single
CPU in the system when we only need to test a subset.

Signed-off-by: Rik van Riel <r...@surriel.com>
---
 include/linux/smp.h |  4 ++++
 kernel/smp.c        | 17 +++++++++++++----
 kernel/up.c         | 14 +++++++++++---
 3 files changed, 28 insertions(+), 7 deletions(-)

diff --git a/include/linux/smp.h b/include/linux/smp.h
index 9fb239e12b82..a56f08ff3097 100644
--- a/include/linux/smp.h
+++ b/include/linux/smp.h
@@ -53,6 +53,10 @@ void on_each_cpu_cond(bool (*cond_func)(int cpu, void *info),
                smp_call_func_t func, void *info, bool wait,
                gfp_t gfp_flags);
 
+void on_each_cpu_cond_mask(bool (*cond_func)(int cpu, void *info),
+               smp_call_func_t func, void *info, bool wait,
+               gfp_t gfp_flags, const struct cpumask *mask);
+
 int smp_call_function_single_async(int cpu, call_single_data_t *csd);
 
 #ifdef CONFIG_SMP
diff --git a/kernel/smp.c b/kernel/smp.c
index 2dbc842dd385..f4cf1b0bb3b8 100644
--- a/kernel/smp.c
+++ b/kernel/smp.c
@@ -667,9 +667,9 @@ EXPORT_SYMBOL(on_each_cpu_mask);
  * You must not call this function with disabled interrupts or
  * from a hardware interrupt handler or from a bottom half handler.
  */
-void on_each_cpu_cond(bool (*cond_func)(int cpu, void *info),
+void on_each_cpu_cond_mask(bool (*cond_func)(int cpu, void *info),
                        smp_call_func_t func, void *info, bool wait,
-                       gfp_t gfp_flags)
+                       gfp_t gfp_flags, const struct cpumask *mask)
 {
        cpumask_var_t cpus;
        int cpu, ret;
@@ -678,7 +678,7 @@ void on_each_cpu_cond(bool (*cond_func)(int cpu, void 
*info),
 
        if (likely(zalloc_cpumask_var(&cpus, (gfp_flags|__GFP_NOWARN)))) {
                preempt_disable();
-               for_each_online_cpu(cpu)
+               for_each_cpu(cpu, mask)
                        if (cond_func(cpu, info))
                                __cpumask_set_cpu(cpu, cpus);
                on_each_cpu_mask(cpus, func, info, wait);
@@ -690,7 +690,7 @@ void on_each_cpu_cond(bool (*cond_func)(int cpu, void 
*info),
                 * just have to IPI them one by one.
                 */
                preempt_disable();
-               for_each_online_cpu(cpu)
+               for_each_cpu(cpu, mask)
                        if (cond_func(cpu, info)) {
                                ret = smp_call_function_single(cpu, func,
                                                                info, wait);
@@ -699,6 +699,15 @@ void on_each_cpu_cond(bool (*cond_func)(int cpu, void 
*info),
                preempt_enable();
        }
 }
+EXPORT_SYMBOL(on_each_cpu_cond_mask);
+
+void on_each_cpu_cond(bool (*cond_func)(int cpu, void *info),
+                       smp_call_func_t func, void *info, bool wait,
+                       gfp_t gfp_flags)
+{
+       on_each_cpu_cond_mask(cond_func, func, info, wait, gfp_flags,
+                               cpu_online_mask);
+}
 EXPORT_SYMBOL(on_each_cpu_cond);
 
 static void do_nothing(void *unused)
diff --git a/kernel/up.c b/kernel/up.c
index 42c46bf3e0a5..ff536f9cc8a2 100644
--- a/kernel/up.c
+++ b/kernel/up.c
@@ -68,9 +68,9 @@ EXPORT_SYMBOL(on_each_cpu_mask);
  * Preemption is disabled here to make sure the cond_func is called under the
  * same condtions in UP and SMP.
  */
-void on_each_cpu_cond(bool (*cond_func)(int cpu, void *info),
-                     smp_call_func_t func, void *info, bool wait,
-                     gfp_t gfp_flags)
+void on_each_cpu_cond_mask(bool (*cond_func)(int cpu, void *info),
+                          smp_call_func_t func, void *info, bool wait,
+                          gfp_t gfp_flags, const struct cpumask *mask)
 {
        unsigned long flags;
 
@@ -82,6 +82,14 @@ void on_each_cpu_cond(bool (*cond_func)(int cpu, void *info),
        }
        preempt_enable();
 }
+EXPORT_SYMBOL(on_each_cpu_cond_mask);
+
+void on_each_cpu_cond(bool (*cond_func)(int cpu, void *info),
+                     smp_call_func_t func, void *info, bool wait,
+                     gfp_t gfp_flags)
+{
+       on_each_cpu_cond_mask(cond_func, func, info, wait, gfp_flags, NULL);
+}
 EXPORT_SYMBOL(on_each_cpu_cond);
 
 int smp_call_on_cpu(unsigned int cpu, int (*func)(void *), void *par, bool 
phys)
-- 
2.17.1