From: Dmitry Torokhov <dtor@chromium.org>
Date: Wed, 4 Feb 2015 21:54:48 +0000 (-0800)
Subject: cpufreq: interactive: fix policy locking
X-Git-Tag: firefly_0821_release~176^2~411
X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=02018626853b6dd6dee77d1e1befeaf2d6a8098e;p=firefly-linux-kernel-4.4.55.git

cpufreq: interactive: fix policy locking

cpufreq_interactive_speedchange_task() is running as a separate kernel
thread and is calling __cpufreq_driver_target(), which requires callers
to hold policy->rwsem for writing to prevent racing with other parts of
the kernel trying to adjust the frequency, for example kernel thermal
throttling. Let's change the code to take policy->rwsem and while at it
refactor the code a bit.

This was originally 2 changes reviewed at:
	https://chromium-review.googlesource.com/246273
	https://chromium-review.googlesource.com/256120

Change-Id: Icc2d97c6c1b929acd2ee32e8c81d81fd2af778ab
Signed-off-by: Dmitry Torokhov <dtor@chromium.org>
Reviewed-by: Dylan Reid <dgreid@chromium.org>
Reviewed-by: Douglas Anderson <dianders@chromium.org>
Signed-off-by: Dmitry Torokhov <dtor@google.com>
---

diff --git a/drivers/cpufreq/cpufreq_interactive.c b/drivers/cpufreq/cpufreq_interactive.c
index 0be66df4a6e6..5224e897d460 100644
--- a/drivers/cpufreq/cpufreq_interactive.c
+++ b/drivers/cpufreq/cpufreq_interactive.c
@@ -511,6 +511,58 @@ static void cpufreq_interactive_idle_end(void)
 	up_read(&pcpu->enable_sem);
 }
 
+static void cpufreq_interactive_get_policy_info(struct cpufreq_policy *policy,
+						unsigned int *pmax_freq,
+						u64 *phvt, u64 *pfvt)
+{
+	struct cpufreq_interactive_cpuinfo *pcpu;
+	unsigned int max_freq = 0;
+	u64 hvt = ~0ULL, fvt = 0;
+	unsigned int i;
+
+	for_each_cpu(i, policy->cpus) {
+		pcpu = &per_cpu(cpuinfo, i);
+
+		fvt = max(fvt, pcpu->loc_floor_val_time);
+		if (pcpu->target_freq > max_freq) {
+			max_freq = pcpu->target_freq;
+			hvt = pcpu->loc_hispeed_val_time;
+		} else if (pcpu->target_freq == max_freq) {
+			hvt = min(hvt, pcpu->loc_hispeed_val_time);
+		}
+	}
+
+	*pmax_freq = max_freq;
+	*phvt = hvt;
+	*pfvt = fvt;
+}
+
+static void cpufreq_interactive_adjust_cpu(unsigned int cpu,
+					   struct cpufreq_policy *policy)
+{
+	struct cpufreq_interactive_cpuinfo *pcpu;
+	u64 hvt, fvt;
+	unsigned int max_freq;
+	int i;
+
+	cpufreq_interactive_get_policy_info(policy, &max_freq, &hvt, &fvt);
+
+	for_each_cpu(i, policy->cpus) {
+		pcpu = &per_cpu(cpuinfo, i);
+		pcpu->pol_floor_val_time = fvt;
+	}
+
+	if (max_freq != policy->cur) {
+		__cpufreq_driver_target(policy, max_freq, CPUFREQ_RELATION_H);
+		for_each_cpu(i, policy->cpus) {
+			pcpu = &per_cpu(cpuinfo, i);
+			pcpu->pol_hispeed_val_time = hvt;
+		}
+	}
+
+	trace_cpufreq_interactive_setspeed(cpu, max_freq, policy->cur);
+}
+
 static int cpufreq_interactive_speedchange_task(void *data)
 {
 	unsigned int cpu;
@@ -539,49 +591,18 @@ static int cpufreq_interactive_speedchange_task(void *data)
 		spin_unlock_irqrestore(&speedchange_cpumask_lock, flags);
 
 		for_each_cpu(cpu, &tmp_mask) {
-			unsigned int j;
-			unsigned int max_freq = 0;
-			struct cpufreq_interactive_cpuinfo *pjcpu;
-			u64 hvt = ~0ULL, fvt = 0;
-
 			pcpu = &per_cpu(cpuinfo, cpu);
-			if (!down_read_trylock(&pcpu->enable_sem))
-				continue;
-			if (!pcpu->governor_enabled) {
-				up_read(&pcpu->enable_sem);
-				continue;
-			}
 
-			for_each_cpu(j, pcpu->policy->cpus) {
-				pjcpu = &per_cpu(cpuinfo, j);
+			down_write(&pcpu->policy->rwsem);
 
-				fvt = max(fvt, pjcpu->loc_floor_val_time);
-				if (pjcpu->target_freq > max_freq) {
-					max_freq = pjcpu->target_freq;
-					hvt = pjcpu->loc_hispeed_val_time;
-				} else if (pjcpu->target_freq == max_freq) {
-					hvt = min(hvt, pjcpu->loc_hispeed_val_time);
-				}
-			}
-			for_each_cpu(j, pcpu->policy->cpus) {
-				pjcpu = &per_cpu(cpuinfo, j);
-				pjcpu->pol_floor_val_time = fvt;
-			}
-
-			if (max_freq != pcpu->policy->cur) {
-				__cpufreq_driver_target(pcpu->policy,
-							max_freq,
-							CPUFREQ_RELATION_H);
-				for_each_cpu(j, pcpu->policy->cpus) {
-					pjcpu = &per_cpu(cpuinfo, j);
-					pjcpu->pol_hispeed_val_time = hvt;
-				}
+			if (likely(down_read_trylock(&pcpu->enable_sem))) {
+				if (likely(pcpu->governor_enabled))
+					cpufreq_interactive_adjust_cpu(cpu,
+							pcpu->policy);
+				up_read(&pcpu->enable_sem);
 			}
-			trace_cpufreq_interactive_setspeed(cpu,
-						     pcpu->target_freq,
-						     pcpu->policy->cur);
 
-			up_read(&pcpu->enable_sem);
+			up_write(&pcpu->policy->rwsem);
 		}
 	}