[PATCH] PM / OPP: Protect updates to list_dev with mutex

Viresh Kumar
2015-10-30T11:56:26Z

dev_opp_list_lock is used everywhere to protect device and OPP lists,
but dev_pm_opp_set_sharing_cpus() is missed somehow. And instead we used
rcu-lock, which wouldn't help here as we are adding a new list_dev.

This also fixes a problem where we have called kzalloc(..., GFP_KERNEL)
from within rcu-lock, which isn't allowed as kzalloc can sleep when
called with GFP_KERNEL.

With CONFIG_DEBUG_ATOMIC_SLEEP set, we will see the caller vomiting.

Fixes: 8d4d4e98acd6 ("PM / OPP: Add helpers for initializing CPU OPPs")
Reported-by: Michael Turquette <mturquette@baylibre.com>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
---
Mike: Can you please verify if this fixes it for you..

drivers/base/power/opp/core.c | 2 +-
drivers/base/power/opp/cpu.c | 8 ++++----
drivers/base/power/opp/opp.h | 3 +++
3 files changed, 8 insertions(+), 5 deletions(-)

diff --git a/drivers/base/power/opp/core.c b/drivers/base/power/opp/core.c
index d5c1149ff123..69f83cbe37b2 100644
--- a/drivers/base/power/opp/core.c
+++ b/drivers/base/power/opp/core.c
@@ -27,7 +27,7 @@
*/
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_MUTEX(dev_opp_list_lock);

#define opp_rcu_lockdep_assert() \
do { \
diff --git a/drivers/base/power/opp/cpu.c b/drivers/base/power/opp/cpu.c
index 7654c5606307..91f15b2e25ee 100644
--- a/drivers/base/power/opp/cpu.c
+++ b/drivers/base/power/opp/cpu.c
@@ -124,12 +124,12 @@ int dev_pm_opp_set_sharing_cpus(struct device *cpu_dev, cpumask_var_t cpumask)
struct device *dev;
int cpu, ret = 0;

- rcu_read_lock();
+ mutex_lock(&dev_opp_list_lock);

dev_opp = _find_device_opp(cpu_dev);
if (IS_ERR(dev_opp)) {
ret = -EINVAL;
- goto out_rcu_read_unlock;
+ goto unlock;
}

for_each_cpu(cpu, cpumask) {
@@ -150,8 +150,8 @@ int dev_pm_opp_set_sharing_cpus(struct device *cpu_dev, cpumask_var_t cpumask)
continue;
}
}
-out_rcu_read_unlock:
- rcu_read_unlock();
+unlock:
+ mutex_unlock(&dev_opp_list_lock);

return 0;
}
diff --git a/drivers/base/power/opp/opp.h b/drivers/base/power/opp/opp.h
index dcb38f78dae4..7366b2aa8997 100644
--- a/drivers/base/power/opp/opp.h
+++ b/drivers/base/power/opp/opp.h
@@ -21,6 +21,9 @@
#include <linux/rculist.h>
#include <linux/rcupdate.h>

+/* Lock to allow exclusive modification to the device and opp lists */
+extern struct mutex dev_opp_list_lock;
+
/*
* Internal data structure organization with the OPP layer library is as
* follows:
--
2.6.2.198.g614a2ac