smp,cpumask: introduce on_each_cpu_cond_mask

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.

Cc: npiggin@gmail.com
Cc: mingo@kernel.org
Cc: will.deacon@arm.com
Cc: songliubraving@fb.com
Cc: kernel-team@fb.com
Cc: hpa@zytor.com
Cc: luto@kernel.org
Signed-off-by: Rik van Riel <riel@surriel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20180926035844.1420-5-riel@surriel.com

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 a7d4f9f50a49..163c451af42e 100644
--- a/kernel/smp.c
+++ b/kernel/smp.c
@@ -669,9 +669,9 @@ 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;
@@ -680,7 +680,7 @@ 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);
@@ -692,7 +692,7 @@ 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);
@@ -701,6 +701,15 @@ 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)