[PATCH v2 3/5] OPP: Allow notifiers to call dev_pm_opp_get_{voltage,freq} RCU-free

Stephen Boyd
2015-09-19T00:53:07Z

We pass the dev_pm_opp structure to OPP notifiers but the users
of the notifier need to surround calls to dev_pm_opp_get_*() with
RCU read locks to avoid lockdep warnings. The notifier is already
called with the dev_opp's srcu lock held, so it should be safe to
assume the devm_pm_opp structure is already protected inside the
notifier. Update the lockdep check for this.

Cc: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>
---
drivers/base/power/opp.c | 19 +++++++++++--------
1 file changed, 11 insertions(+), 8 deletions(-)

diff --git a/drivers/base/power/opp.c b/drivers/base/power/opp.c
index 35b66c46dcb7..1d8c45e53245 100644
--- a/drivers/base/power/opp.c
+++ b/drivers/base/power/opp.c
@@ -146,9 +146,10 @@ static LIST_HEAD(dev_opp_list);
/* Lock to allow exclusive modification to the device and opp lists */
static DEFINE_MUTEX(dev_opp_list_lock);

-#define opp_rcu_lockdep_assert() \
+#define opp_rcu_lockdep_assert(s) \
do { \
RCU_LOCKDEP_WARN(!rcu_read_lock_held() && \
+ !(s && srcu_read_lock_held(s)) && \
!lockdep_is_held(&dev_opp_list_lock), \
"Missing rcu_read_lock() or " \
"dev_opp_list_lock protection"); \
@@ -236,9 +237,10 @@ unsigned long dev_pm_opp_get_voltage(struct dev_pm_opp *opp)
struct dev_pm_opp *tmp_opp;
unsigned long v = 0;

- opp_rcu_lockdep_assert();
+ opp_rcu_lockdep_assert(&opp->dev_opp->srcu_head.srcu);

- tmp_opp = rcu_dereference(opp);
+ tmp_opp = srcu_dereference_check(opp, &opp->dev_opp->srcu_head.srcu,
+ rcu_read_lock_held());
if (IS_ERR_OR_NULL(tmp_opp) || !tmp_opp->available)
pr_err("%s: Invalid parameters\n", __func__);
else
@@ -268,9 +270,10 @@ unsigned long dev_pm_opp_get_freq(struct dev_pm_opp *opp)
struct dev_pm_opp *tmp_opp;
unsigned long f = 0;

- opp_rcu_lockdep_assert();
+ opp_rcu_lockdep_assert(&opp->dev_opp->srcu_head.srcu);

- tmp_opp = rcu_dereference(opp);
+ tmp_opp = srcu_dereference_check(opp, &opp->dev_opp->srcu_head.srcu,
+ rcu_read_lock_held());
if (IS_ERR_OR_NULL(tmp_opp) || !tmp_opp->available)
pr_err("%s: Invalid parameters\n", __func__);
else
@@ -437,7 +440,7 @@ struct dev_pm_opp *dev_pm_opp_find_freq_exact(struct device *dev,
struct device_opp *dev_opp;
struct dev_pm_opp *temp_opp, *opp = ERR_PTR(-ERANGE);

- opp_rcu_lockdep_assert();
+ opp_rcu_lockdep_assert(NULL);

dev_opp = _find_device_opp(dev);
if (IS_ERR(dev_opp)) {
@@ -485,7 +488,7 @@ struct dev_pm_opp *dev_pm_opp_find_freq_ceil(struct device *dev,
struct device_opp *dev_opp;
struct dev_pm_opp *temp_opp, *opp = ERR_PTR(-ERANGE);

- opp_rcu_lockdep_assert();
+ opp_rcu_lockdep_assert(NULL);

if (!dev || !freq) {
dev_err(dev, "%s: Invalid argument freq=%p\n", __func__, freq);
@@ -535,7 +538,7 @@ struct dev_pm_opp *dev_pm_opp_find_freq_floor(struct device *dev,
struct device_opp *dev_opp;
struct dev_pm_opp *temp_opp, *opp = ERR_PTR(-ERANGE);

- opp_rcu_lockdep_assert();
+ opp_rcu_lockdep_assert(NULL);

if (!dev || !freq) {
dev_err(dev, "%s: Invalid argument freq=%p\n", __func__, freq);
--
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