From 25fb6e6164b107f1674ec32f0d0e47328c2c11a6 Mon Sep 17 00:00:00 2001 Message-Id: <25fb6e6164b107f1674ec32f0d0e47328c2c11a6.1372079234.git.viresh.kumar@linaro.org> From: Viresh Kumar Date: Wed, 19 Jun 2013 10:16:55 +0530 Subject: [PATCH] cpufreq: make sure frequency transitions are serialized Whenever we are changing frequency of a cpu, we are calling PRECHANGE and POSTCHANGE notifiers. They must be serialized. i.e. PRECHANGE or POSTCHANGE shouldn't be called twice contiguously. This can happen due to bugs in users of __cpufreq_driver_target() or actual cpufreq drivers who are sending these notifiers. This patch adds some protection against this. Now, we keep track of the last transaction and see if something went wrong. Signed-off-by: Viresh Kumar --- drivers/cpufreq/cpufreq.c | 19 +++++++++++++++++++ 1 file changed, 19 insertions(+) diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c index 2d53f47..6624694 100644 --- a/drivers/cpufreq/cpufreq.c +++ b/drivers/cpufreq/cpufreq.c @@ -107,6 +107,9 @@ static void handle_update(struct work_struct *work); static BLOCKING_NOTIFIER_HEAD(cpufreq_policy_notifier_list); static struct srcu_notifier_head cpufreq_transition_notifier_list; +/* Tracks status of transition */ +static int transition_ongoing; + static bool init_cpufreq_transition_notifier_list_called; static int __init init_cpufreq_transition_notifier_list(void) { @@ -264,6 +267,13 @@ void __cpufreq_notify_transition(struct cpufreq_policy *policy, switch (state) { case CPUFREQ_PRECHANGE: + if (transition_ongoing) { + WARN(1, "In middle of another frequency transition\n"); + return; + } + + transition_ongoing++; + /* detect if the driver reported a value as "old frequency" * which is not equal to what the cpufreq core thinks is * "old frequency". @@ -283,6 +293,13 @@ void __cpufreq_notify_transition(struct cpufreq_policy *policy, break; case CPUFREQ_POSTCHANGE: + if (!transition_ongoing) { + WARN(1, "No frequency transition in progress\n"); + return; + } + + transition_ongoing--; + adjust_jiffies(CPUFREQ_POSTCHANGE, freqs); pr_debug("FREQ: %lu - CPU: %lu", (unsigned long)freqs->new, (unsigned long)freqs->cpu); @@ -1458,6 +1475,8 @@ int __cpufreq_driver_target(struct cpufreq_policy *policy, if (cpufreq_disabled()) return -ENODEV; + if (transition_ongoing) + return -EBUSY; /* Make sure that target_freq is within supported range */ if (target_freq > policy->max) -- 1.7.12.rc2.18.g61b472e