[tip:sched/core] smp: Add new wake_up_all_idle_cpus() function

[tip-bot for Chuansheng Liu]

Commit-ID:  c6f4459fc3ba532e896cb678e29b45cb985f82bf
Gitweb:     http://git.kernel.org/tip/c6f4459fc3ba532e896cb678e29b45cb985f82bf
Author:     Chuansheng Liu <chuansheng.liu@xxxxxxxxx>
AuthorDate: Thu, 4 Sep 2014 15:17:54 +0800
Committer:  Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Fri, 19 Sep 2014 12:35:15 +0200

smp: Add new wake_up_all_idle_cpus() function

Currently kick_all_cpus_sync() can break non-polling idle cpus
thru IPI interrupts.

But sometimes we need to break the polling idle cpus immediately
to reselect the suitable c-state, also for non-idle cpus, we need
to do nothing if we try to wake up them.

Here adding one new function wake_up_all_idle_cpus() to let all cpus
out of idle based on function wake_up_if_idle().

Signed-off-by: Chuansheng Liu <chuansheng.liu@xxxxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Cc: daniel.lezcano@xxxxxxxxxx
Cc: rjw@xxxxxxxxxxxxx
Cc: linux-pm@xxxxxxxxxxxxxxx
Cc: changcheng.liu@xxxxxxxxx
Cc: xiaoming.wang@xxxxxxxxx
Cc: souvik.k.chakravarty@xxxxxxxxx
Cc: luto@xxxxxxxxxxxxxx
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Christoph Hellwig <hch@xxxxxxxxxxxxx>
Cc: Frederic Weisbecker <fweisbec@xxxxxxxxx>
Cc: Geert Uytterhoeven <geert+renesas@xxxxxxxxx>
Cc: Jan Kara <jack@xxxxxxx>
Cc: Jens Axboe <axboe@xxxxxx>
Cc: Jens Axboe <axboe@xxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxx>
Cc: Paul Gortmaker <paul.gortmaker@xxxxxxxxxxxxx>
Cc: Roman Gushchin <klamm@xxxxxxxxxxxxxx>
Cc: Srivatsa S. Bhat <srivatsa.bhat@xxxxxxxxxxxxxxxxxx>
Link: http://lkml.kernel.org/r/1409815075-4180-2-git-send-email-chuansheng.liu@xxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
 include/linux/smp.h |  2 ++
 kernel/smp.c        | 22 ++++++++++++++++++++++
 2 files changed, 24 insertions(+)

diff --git a/include/linux/smp.h b/include/linux/smp.h
index 34347f2..93dff5f 100644
--- a/include/linux/smp.h
+++ b/include/linux/smp.h
@@ -100,6 +100,7 @@ int smp_call_function_any(const struct cpumask *mask,
 			  smp_call_func_t func, void *info, int wait);
 
 void kick_all_cpus_sync(void);
+void wake_up_all_idle_cpus(void);
 
 /*
  * Generic and arch helpers
@@ -148,6 +149,7 @@ smp_call_function_any(const struct cpumask *mask, smp_call_func_t func,
 }
 
 static inline void kick_all_cpus_sync(void) {  }
+static inline void wake_up_all_idle_cpus(void) {  }
 
 #endif /* !SMP */
 
diff --git a/kernel/smp.c b/kernel/smp.c
index aff8aa1..9e0d0b2 100644
--- a/kernel/smp.c
+++ b/kernel/smp.c
@@ -13,6 +13,7 @@
 #include <linux/gfp.h>
 #include <linux/smp.h>
 #include <linux/cpu.h>
+#include <linux/sched.h>
 
 #include "smpboot.h"
 
@@ -699,3 +700,24 @@ void kick_all_cpus_sync(void)
 	smp_call_function(do_nothing, NULL, 1);
 }
 EXPORT_SYMBOL_GPL(kick_all_cpus_sync);
+
+/**
+ * wake_up_all_idle_cpus - break all cpus out of idle
+ * wake_up_all_idle_cpus try to break all cpus which is in idle state even
+ * including idle polling cpus, for non-idle cpus, we will do nothing
+ * for them.
+ */
+void wake_up_all_idle_cpus(void)
+{
+	int cpu;
+
+	preempt_disable();
+	for_each_online_cpu(cpu) {
+		if (cpu == smp_processor_id())
+			continue;
+
+		wake_up_if_idle(cpu);
+	}
+	preempt_enable();
+}
+EXPORT_SYMBOL_GPL(wake_up_all_idle_cpus);
--
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