From 12641505653f491f414406a1b5dd35876f61cfb8 Mon Sep 17 00:00:00 2001
From: Colin Cross <ccross@android.com>
Date: Mon, 7 May 2012 17:57:42 -0700
Subject: [PATCH] --- yaml --- r: 318810 b: refs/heads/master c:
 20ff51a36b2cd25ee7eb3216b6d02b68935435ba h: refs/heads/master v: v3

---
 [refs]                          |  2 +-
 trunk/drivers/cpuidle/coupled.c | 37 +++++++++++++++++++++++++++++++++
 trunk/include/linux/cpuidle.h   |  4 ++++
 3 files changed, 42 insertions(+), 1 deletion(-)

diff --git a/[refs] b/[refs]
index 94f66c6105c4..3ad6c57c2c17 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 4126c0197bc8c58a0bb7fcda07b01b596b6fb4c5
+refs/heads/master: 20ff51a36b2cd25ee7eb3216b6d02b68935435ba
diff --git a/trunk/drivers/cpuidle/coupled.c b/trunk/drivers/cpuidle/coupled.c
index aab6bba8daec..2c9bf2692232 100644
--- a/trunk/drivers/cpuidle/coupled.c
+++ b/trunk/drivers/cpuidle/coupled.c
@@ -129,6 +129,43 @@ static DEFINE_PER_CPU(struct call_single_data, cpuidle_coupled_poke_cb);
  */
 static cpumask_t cpuidle_coupled_poked_mask;
 
+/**
+ * cpuidle_coupled_parallel_barrier - synchronize all online coupled cpus
+ * @dev: cpuidle_device of the calling cpu
+ * @a:   atomic variable to hold the barrier
+ *
+ * No caller to this function will return from this function until all online
+ * cpus in the same coupled group have called this function.  Once any caller
+ * has returned from this function, the barrier is immediately available for
+ * reuse.
+ *
+ * The atomic variable a must be initialized to 0 before any cpu calls
+ * this function, will be reset to 0 before any cpu returns from this function.
+ *
+ * Must only be called from within a coupled idle state handler
+ * (state.enter when state.flags has CPUIDLE_FLAG_COUPLED set).
+ *
+ * Provides full smp barrier semantics before and after calling.
+ */
+void cpuidle_coupled_parallel_barrier(struct cpuidle_device *dev, atomic_t *a)
+{
+	int n = dev->coupled->online_count;
+
+	smp_mb__before_atomic_inc();
+	atomic_inc(a);
+
+	while (atomic_read(a) < n)
+		cpu_relax();
+
+	if (atomic_inc_return(a) == n * 2) {
+		atomic_set(a, 0);
+		return;
+	}
+
+	while (atomic_read(a) > n)
+		cpu_relax();
+}
+
 /**
  * cpuidle_state_is_coupled - check if a state is part of a coupled set
  * @dev: struct cpuidle_device for the current cpu
diff --git a/trunk/include/linux/cpuidle.h b/trunk/include/linux/cpuidle.h
index 603844835bc7..5ab7183313ce 100644
--- a/trunk/include/linux/cpuidle.h
+++ b/trunk/include/linux/cpuidle.h
@@ -183,6 +183,10 @@ static inline int cpuidle_play_dead(void) {return -ENODEV; }
 
 #endif
 
+#ifdef CONFIG_ARCH_NEEDS_CPU_IDLE_COUPLED
+void cpuidle_coupled_parallel_barrier(struct cpuidle_device *dev, atomic_t *a);
+#endif
+
 /******************************
  * CPUIDLE GOVERNOR INTERFACE *
  ******************************/