arm: mach-tegra: resolve tegra_cpu_lock race condition

Problem description:

 - lock used in cpuquiet, cpu-tegra3.c, tegra2-throttle.c, and tegra3_throttle
   originate from cpu-tegra.c, tegra_cpu_lock
 - edp_update_limit and tegra_auto_hotplug_governor need a protection from
   tegra_cpu_lock. These are also called by tegra_cpu_set_speed_cap
 - Some callers of tegra_cpu_set_speed_cap do not acquire tegra_cpu_lock,
   but some do

Fix description:

 - Create a locked variant and unlocked variant of tegra_cpu_set_speed_cap
   to make it explicit that tegra_cpu_lock is needed for tegra_cpu_set_speed_cap
 - Replace existing calls with new variants of tegra_cpu_set_speed_cap appropriately

Bug 1225764

Change-Id: I8aa6356df278375e3a9105023f66c8286e3fdbef
Signed-off-by: Sang-Hun Lee <sanlee@nvidia.com>
Reviewed-on: http://git-master/r/199238
(cherry picked from commit 91bdd64c3c80480195a5ccdb8cef969ca5a18afc)
Reviewed-on: http://git-master/r/207640
Reviewed-by: Automatic_Commit_Validation_User
Reviewed-by: Bharat Nihalani <bnihalani@nvidia.com>

5 files changed, 40 insertions, 26 deletions

diff --git a/arch/arm/mach-tegra/cpu-tegra.c b/arch/arm/mach-tegra/cpu-tegra.c
index d864e9b96ba4..854f34777b8f 100644
--- a/arch/arm/mach-tegra/cpu-tegra.c
+++ b/arch/arm/mach-tegra/cpu-tegra.c
@@ -7,7 +7,7 @@
  *	Colin Cross <ccross@google.com>
  *	Based on arch/arm/plat-omap/cpu-omap.c, (C) 2005 Nokia Corporation
  *
- * Copyright (C) 2010-2012 NVIDIA CORPORATION. All rights reserved.
+ * Copyright (C) 2010-2013 NVIDIA CORPORATION. All rights reserved.
  *
  * This software is licensed under the terms of the GNU General Public
  * License version 2, as published by the Free Software Foundation, and
@@ -66,7 +66,7 @@ static int force_policy_max_set(const char *arg, const struct kernel_param *kp)
 
 	ret = param_set_bool(arg, kp);
 	if ((ret == 0) && (old_policy != force_policy_max))
-		tegra_cpu_set_speed_cap(NULL);
+		tegra_cpu_set_speed_cap_locked(NULL);
 
 	mutex_unlock(&tegra_cpu_lock);
 	return ret;
@@ -99,7 +99,7 @@ static inline void _cpu_user_cap_set_locked(void)
 		cpu_user_cap = freq_table[i].frequency;
 	}
 #endif
-	tegra_cpu_set_speed_cap(NULL);
+	tegra_cpu_set_speed_cap_locked(NULL);
 }
 
 void tegra_cpu_user_cap_set(unsigned int speed_khz)
@@ -212,10 +212,11 @@ static unsigned int edp_predict_limit(unsigned int cpus)
 	return limit;
 }
 
+/* Must be called while holding cpu_tegra_lock */
 static void edp_update_limit(void)
 {
 	unsigned int limit = edp_predict_limit(cpumask_weight(&edp_cpumask));
-
+	BUG_ON(!mutex_is_locked(&tegra_cpu_lock));
 #ifdef CONFIG_TEGRA_EDP_EXACT_FREQ
 	edp_limit = limit;
 #else
@@ -263,7 +264,7 @@ int tegra_edp_set_cur_state(struct thermal_cooling_device *cdev,
 	tegra_cpu_dvfs_alter(edp_thermal_index, &edp_cpumask, true, 0);
 	if (target_cpu_speed[0]) {
 		edp_update_limit();
-		tegra_cpu_set_speed_cap(NULL);
+		tegra_cpu_set_speed_cap_locked(NULL);
 	}
 	tegra_cpu_dvfs_alter(edp_thermal_index, &edp_cpumask, false, 0);
 	mutex_unlock(&tegra_cpu_lock);
@@ -299,7 +300,7 @@ int tegra_system_edp_alarm(bool alarm)
 	   or alarm is canceled */
 	if (target_cpu_speed[0]) {
 		edp_update_limit();
-		ret = tegra_cpu_set_speed_cap(NULL);
+		ret = tegra_cpu_set_speed_cap_locked(NULL);
 	}
 	if (!ret || !alarm)
 		tegra_edp_throttle_cpu_now(0);
@@ -359,7 +360,7 @@ static int tegra_cpu_edp_notify(
 		cpu_speed = tegra_getspeed(0);
 		new_speed = edp_governor_speed(cpu_speed);
 		if (new_speed < cpu_speed) {
-			ret = tegra_cpu_set_speed_cap(NULL);
+			ret = tegra_cpu_set_speed_cap_locked(NULL);
 			printk(KERN_DEBUG "cpu-tegra:%sforce EDP limit %u kHz"
 				"\n", ret ? " failed to " : " ", new_speed);
 		}
@@ -378,7 +379,7 @@ static int tegra_cpu_edp_notify(
 		tegra_cpu_dvfs_alter(
 			edp_thermal_index, &edp_cpumask, true, event);
 		edp_update_limit();
-		tegra_cpu_set_speed_cap(NULL);
+		tegra_cpu_set_speed_cap_locked(NULL);
 		mutex_unlock(&tegra_cpu_lock);
 		break;
 	}
@@ -615,7 +616,7 @@ void tegra_cpu_set_volt_cap(unsigned int cap)
 	mutex_lock(&tegra_cpu_lock);
 	if (cap != volt_capped_speed) {
 		volt_capped_speed = cap;
-		tegra_cpu_set_speed_cap(NULL);
+		tegra_cpu_set_speed_cap_locked(NULL);
 	}
 	mutex_unlock(&tegra_cpu_lock);
 	if (cap)
@@ -631,11 +632,12 @@ static unsigned int volt_cap_speed(unsigned int requested_speed)
 	return requested_speed;
 }
 
-int tegra_cpu_set_speed_cap(unsigned int *speed_cap)
+/* Must be called with tegra_cpu_lock held */
+int tegra_cpu_set_speed_cap_locked(unsigned int *speed_cap)
 {
 	int ret = 0;
 	unsigned int new_speed = tegra_cpu_highest_speed();
-
+	BUG_ON(!mutex_is_locked(&tegra_cpu_lock));
 #ifdef CONFIG_TEGRA_EDP_LIMITS
 	edp_update_limit();
 #endif
@@ -656,6 +658,16 @@ int tegra_cpu_set_speed_cap(unsigned int *speed_cap)
 	return ret;
 }
 
+int tegra_cpu_set_speed_cap(unsigned int *speed_cap)
+{
+	int ret;
+	mutex_lock(&tegra_cpu_lock);
+	ret = tegra_cpu_set_speed_cap_locked(speed_cap);
+	mutex_unlock(&tegra_cpu_lock);
+	return ret;
+}
+
+
 int tegra_suspended_target(unsigned int target_freq)
 {
 	unsigned int new_speed = target_freq;
@@ -689,7 +701,7 @@ static int tegra_target(struct cpufreq_policy *policy,
 	freq = freq_table[idx].frequency;
 
 	target_cpu_speed[policy->cpu] = freq;
-	ret = tegra_cpu_set_speed_cap(&new_speed);
+	ret = tegra_cpu_set_speed_cap_locked(&new_speed);
 _out:
 	mutex_unlock(&tegra_cpu_lock);
 
@@ -712,7 +724,7 @@ static int tegra_pm_notify(struct notifier_block *nb, unsigned long event,
 		unsigned int freq;
 		is_suspended = false;
 		tegra_cpu_edp_init(true);
-		tegra_cpu_set_speed_cap(&freq);
+		tegra_cpu_set_speed_cap_locked(&freq);
 		pr_info("Tegra cpufreq resume: restoring frequency to %d kHz\n",
 			freq);
 	}
@@ -844,7 +856,9 @@ static int __init tegra_cpufreq_init(void)
 		return ret;
 
 	freq_table = table_data->freq_table;
+	mutex_lock(&tegra_cpu_lock);
 	tegra_cpu_edp_init(false);
+	mutex_unlock(&tegra_cpu_lock);
 
 	ret = register_pm_notifier(&tegra_cpu_pm_notifier);
 
diff --git a/arch/arm/mach-tegra/cpu-tegra.h b/arch/arm/mach-tegra/cpu-tegra.h
index 749ec6345cfa..84504bb0ccc1 100644
--- a/arch/arm/mach-tegra/cpu-tegra.h
+++ b/arch/arm/mach-tegra/cpu-tegra.h
@@ -1,7 +1,7 @@
 /*
  * arch/arm/mach-tegra/cpu-tegra.h
  *
- * Copyright (c) 2011-2012, NVIDIA Corporation.
+ * Copyright (c) 2011-2013, NVIDIA Corporation.
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
@@ -27,6 +27,7 @@
 unsigned int tegra_getspeed(unsigned int cpu);
 int tegra_update_cpu_speed(unsigned long rate);
 int tegra_cpu_set_speed_cap(unsigned int *speed_cap);
+int tegra_cpu_set_speed_cap_locked(unsigned int *speed_cap);
 void tegra_cpu_set_volt_cap(unsigned int cap);
 unsigned int tegra_count_slow_cpus(unsigned long speed_limit);
 unsigned int tegra_get_slowest_cpu_n(void);
diff --git a/arch/arm/mach-tegra/cpu-tegra3.c b/arch/arm/mach-tegra/cpu-tegra3.c
index f26f449b482b..d7d0250e424e 100644
--- a/arch/arm/mach-tegra/cpu-tegra3.c
+++ b/arch/arm/mach-tegra/cpu-tegra3.c
@@ -3,7 +3,7 @@
  *
  * CPU auto-hotplug for Tegra3 CPUs
  *
- * Copyright (c) 2011-2012, NVIDIA Corporation. All rights reserved.
+ * Copyright (c) 2011-2013, NVIDIA Corporation. All rights reserved.
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
@@ -43,6 +43,7 @@
 #define UP2Gn_DELAY_MS		100
 #define DOWN_DELAY_MS		2000
 
+/* tegra3_cpu_lock is tegra_cpu_lock from cpu-tegra.c */
 static struct mutex *tegra3_cpu_lock;
 
 static struct workqueue_struct *hotplug_wq;
@@ -160,7 +161,7 @@ static int hp_state_set(const char *arg, const struct kernel_param *kp)
 				hp_init_stats();
 			}
 			/* catch-up with governor target speed */
-			tegra_cpu_set_speed_cap(NULL);
+			tegra_cpu_set_speed_cap_locked(NULL);
 		}
 	} else
 		pr_warn("%s: unable to set tegra hotplug state %s\n",
@@ -295,7 +296,7 @@ static void __cpuinit tegra_auto_hotplug_work_func(struct work_struct *work)
 				hp_stats_update(CONFIG_NR_CPUS, true);
 				hp_stats_update(0, false);
 				/* catch-up with governor target speed */
-				tegra_cpu_set_speed_cap(NULL);
+				tegra_cpu_set_speed_cap_locked(NULL);
 				break;
 			}
 		}
@@ -309,7 +310,7 @@ static void __cpuinit tegra_auto_hotplug_work_func(struct work_struct *work)
 				hp_stats_update(CONFIG_NR_CPUS, false);
 				hp_stats_update(0, true);
 				/* catch-up with governor target speed */
-				tegra_cpu_set_speed_cap(NULL);
+				tegra_cpu_set_speed_cap_locked(NULL);
 			}
 		} else {
 			switch (tegra_cpu_speed_balance()) {
@@ -373,7 +374,7 @@ static int min_cpus_notify(struct notifier_block *nb, unsigned long n, void *p)
 		}
 	}
 	/* update governor state machine */
-	tegra_cpu_set_speed_cap(NULL);
+	tegra_cpu_set_speed_cap_locked(NULL);
 	mutex_unlock(tegra3_cpu_lock);
 	return NOTIFY_OK;
 }
diff --git a/arch/arm/mach-tegra/cpuquiet.c b/arch/arm/mach-tegra/cpuquiet.c
index a617fa262f46..a66cd52f435f 100644
--- a/arch/arm/mach-tegra/cpuquiet.c
+++ b/arch/arm/mach-tegra/cpuquiet.c
@@ -3,7 +3,7 @@
  *
  * Cpuquiet driver for Tegra CPUs
  *
- * Copyright (c) 2012 NVIDIA CORPORATION.  All rights reserved.
+ * Copyright (c) 2012-2013 NVIDIA CORPORATION.  All rights reserved.
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
@@ -371,6 +371,7 @@ static void __cpuinit tegra_cpuquiet_work_func(struct work_struct *work)
 		current_cluster = __apply_cluster_config(current_cluster,
 					new_cluster);
 
+		tegra_cpu_set_speed_cap_locked(NULL);
 		mutex_unlock(tegra_cpu_lock);
 
 		if (current_cluster == TEGRA_CPQ_LP)
@@ -378,9 +379,9 @@ static void __cpuinit tegra_cpuquiet_work_func(struct work_struct *work)
 		else
 			cpuquiet_device_free();
 
-		tegra_cpu_set_speed_cap(NULL);
-	} else
+	} else {
 		mutex_unlock(tegra_cpu_lock);
+	}
 
 	if (current_cluster == TEGRA_CPQ_G)
 		__apply_core_config();
diff --git a/arch/arm/mach-tegra/tegra3_throttle.c b/arch/arm/mach-tegra/tegra3_throttle.c
index 62ba41b5b79d..90ab7c4b6dec 100644
--- a/arch/arm/mach-tegra/tegra3_throttle.c
+++ b/arch/arm/mach-tegra/tegra3_throttle.c
@@ -33,6 +33,7 @@
 #include "clock.h"
 #include "cpu-tegra.h"
 
+/* cpu_throttle_lock is tegra_cpu_lock from cpu-tegra.c */
 static struct mutex *cpu_throttle_lock;
 static DEFINE_MUTEX(bthrot_list_lock);
 static LIST_HEAD(bthrot_list);
@@ -218,9 +219,7 @@ tegra_throttle_set_cur_state(struct thermal_cooling_device *cdev,
 	if (cur_state == 0) {
 		tegra_throttle_cap_freqs_update(NULL, -1, 1);/* uncap freqs */
 
-		mutex_lock(cpu_throttle_lock);
 		tegra_cpu_set_speed_cap(NULL);
-		mutex_unlock(cpu_throttle_lock);
 	} else {
 		if (cur_state == 1 && direction == 0)
 			bthrot->throttle_count++;
@@ -234,9 +233,7 @@ tegra_throttle_set_cur_state(struct thermal_cooling_device *cdev,
 			bthrot->cpu_cap_freq =
 					bthrot->throt_tab[index].cap_freqs[0];
 
-			mutex_lock(cpu_throttle_lock);
 			tegra_cpu_set_speed_cap(NULL);
-			mutex_unlock(cpu_throttle_lock);
 		}
 	}