| Message ID | 0bebf56a27f799a282cc00d0c17c187f9941f122.1371630975.git.viresh.kumar@linaro.org |
|---|---|
| State | Accepted |
| Headers | show |
On Wednesday, June 19, 2013 02:23:07 PM Viresh Kumar wrote: > 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 <viresh.kumar@linaro.org> > --- > drivers/cpufreq/cpufreq.c | 9 +++++++++ > 1 file changed, 9 insertions(+) > > diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c > index 2d53f47..92cb8b3 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 +267,8 @@ void __cpufreq_notify_transition(struct cpufreq_policy *policy, > switch (state) { > > case CPUFREQ_PRECHANGE: > + WARN_ON(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 +288,8 @@ void __cpufreq_notify_transition(struct cpufreq_policy *policy, > break; > > case CPUFREQ_POSTCHANGE: > + WARN_ON(!transition_ongoing--); Shouldn't we try to avoid going into the negative range here? > + > adjust_jiffies(CPUFREQ_POSTCHANGE, freqs); > pr_debug("FREQ: %lu - CPU: %lu", (unsigned long)freqs->new, > (unsigned long)freqs->cpu); > @@ -1458,6 +1465,8 @@ 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) > Rafael
diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c index 2d53f47..92cb8b3 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 +267,8 @@ void __cpufreq_notify_transition(struct cpufreq_policy *policy, switch (state) { case CPUFREQ_PRECHANGE: + WARN_ON(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 +288,8 @@ void __cpufreq_notify_transition(struct cpufreq_policy *policy, break; case CPUFREQ_POSTCHANGE: + WARN_ON(!transition_ongoing--); + adjust_jiffies(CPUFREQ_POSTCHANGE, freqs); pr_debug("FREQ: %lu - CPU: %lu", (unsigned long)freqs->new, (unsigned long)freqs->cpu); @@ -1458,6 +1465,8 @@ 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)
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 <viresh.kumar@linaro.org> --- drivers/cpufreq/cpufreq.c | 9 +++++++++ 1 file changed, 9 insertions(+)