From: Park Bumgyu <bumgyu.park@samsung.com>
Date: Thu, 5 Apr 2018 05:36:40 +0000 (+0900)
Subject: sched: ems: avoid to access empty energy table
X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=0b010e6e5f5dacdcc1d67f7adee38f5f8a7cdf6e;p=GitHub%2FLineageOS%2Fandroid_kernel_motorola_exynos9610.git

sched: ems: avoid to access empty energy table

Accessing the energy table without allocation cause a NULL pointer
exception. energy_table.nr_states have values after the energy table
created, so check the nr_states to avoid problem.

Change-Id: I90d6c9b8ff5ac0eb67b92ab0bb57b911d8f65091
Signed-off-by: Park Bumgyu <bumgyu.park@samsung.com>
---

diff --git a/kernel/sched/ems/core.c b/kernel/sched/ems/core.c
index 26f2e65f800b..b24d3f76db63 100644
--- a/kernel/sched/ems/core.c
+++ b/kernel/sched/ems/core.c
@@ -32,6 +32,13 @@ static int cpu_util_wake(int cpu, struct task_struct *p)
 	return (util >= capacity) ? capacity : util;
 }
 
+struct energy_table {
+	struct capacity_state *states;
+	unsigned int nr_states;
+};
+
+DEFINE_PER_CPU(struct energy_table, energy_table);
+
 struct eco_env {
 	struct task_struct *p;
 
@@ -51,6 +58,13 @@ static void find_eco_target(struct eco_env *eenv)
 	int backup_cpu = -1;
 	int cpu;
 
+	/*
+	 * It is meaningless to find an energy cpu when the energy table is
+	 * not created or has not been created yet.
+	 */
+	if (!per_cpu(energy_table, eenv->prev_cpu).nr_states)
+		return;
+
 	rcu_read_lock();
 
 	for_each_cpu_and(cpu, &p->cpus_allowed, cpu_active_mask) {
@@ -125,13 +139,6 @@ static void find_eco_target(struct eco_env *eenv)
 	eenv->backup_cpu = backup_cpu;
 }
 
-struct energy_table {
-	struct capacity_state *states;
-	unsigned int nr_states;
-};
-
-DEFINE_PER_CPU(struct energy_table, energy_table);
-
 static unsigned int calculate_energy(struct task_struct *p, int target_cpu)
 {
 	unsigned long util[NR_CPUS] = {0, };
@@ -274,6 +281,8 @@ select_energy_cpu(struct task_struct *p, int prev_cpu, int sd_flag, int sync)
 	struct eco_env eenv = {
 		.p = p,
 		.prev_cpu = prev_cpu,
+		.best_cpu = -1,
+		.backup_cpu = -1,
 	};
 
 	if (!sched_feat(ENERGY_AWARE))