[PATCH 2/3] smp: Adding new function wake_up_all_cpus()

Chuansheng Liu
2014-08-18T08:52:08Z

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_cpus() to let all cpus out
of idle based on function wake_up_if_idle().

Signed-off-by: Chuansheng Liu <chuansheng.liu@intel.com>
---
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..1cfb1fd 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_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_cpus(void) { }

#endif /* !SMP */

diff --git a/kernel/smp.c b/kernel/smp.c
index aff8aa1..1e69507 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_cpus - break all cpus out of idle
+ * wake_up_all_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_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_cpus);
--
1.7.9.5