i2c: Prevent priority inversion on top of bus lock
Low priority thread holding the i2c bus mutex could block higher
priority threads to access the bus resulting in unacceptable
latencies. Change the mutex type to rt_mutex preventing priority
inversion.
Tested-by: Peter Ujfalusi <peter.ujfalusi@nokia.com>
Signed-off-by: Mika Kuoppala <mika.kuoppala@nokia.com>
Signed-off-by: Jean Delvare <khali@linux-fr.org>
diff --git a/drivers/i2c/Kconfig b/drivers/i2c/Kconfig
index d7ece13..8d8a00e 100644
--- a/drivers/i2c/Kconfig
+++ b/drivers/i2c/Kconfig
@@ -5,6 +5,7 @@
menuconfig I2C
tristate "I2C support"
depends on HAS_IOMEM
+ select RT_MUTEXES
---help---
I2C (pronounce: I-square-C) is a slow serial bus protocol used in
many micro controller applications and developed by Philips. SMBus,
diff --git a/drivers/i2c/i2c-core.c b/drivers/i2c/i2c-core.c
index 2965043..d664b4a 100644
--- a/drivers/i2c/i2c-core.c
+++ b/drivers/i2c/i2c-core.c
@@ -584,7 +584,7 @@
goto out_list;
}
- mutex_init(&adap->bus_lock);
+ rt_mutex_init(&adap->bus_lock);
/* Set default timeout to 1 second if not already set */
if (adap->timeout == 0)
@@ -1092,12 +1092,12 @@
#endif
if (in_atomic() || irqs_disabled()) {
- ret = mutex_trylock(&adap->bus_lock);
+ ret = rt_mutex_trylock(&adap->bus_lock);
if (!ret)
/* I2C activity is ongoing. */
return -EAGAIN;
} else {
- mutex_lock_nested(&adap->bus_lock, adap->level);
+ rt_mutex_lock(&adap->bus_lock);
}
/* Retry automatically on arbitration loss */
@@ -1109,7 +1109,7 @@
if (time_after(jiffies, orig_jiffies + adap->timeout))
break;
}
- mutex_unlock(&adap->bus_lock);
+ rt_mutex_unlock(&adap->bus_lock);
return ret;
} else {
@@ -1913,7 +1913,7 @@
flags &= I2C_M_TEN | I2C_CLIENT_PEC;
if (adapter->algo->smbus_xfer) {
- mutex_lock(&adapter->bus_lock);
+ rt_mutex_lock(&adapter->bus_lock);
/* Retry automatically on arbitration loss */
orig_jiffies = jiffies;
@@ -1927,7 +1927,7 @@
orig_jiffies + adapter->timeout))
break;
}
- mutex_unlock(&adapter->bus_lock);
+ rt_mutex_unlock(&adapter->bus_lock);
} else
res = i2c_smbus_xfer_emulated(adapter,addr,flags,read_write,
command, protocol, data);
diff --git a/include/linux/i2c.h b/include/linux/i2c.h
index 7b40cda..52317fb 100644
--- a/include/linux/i2c.h
+++ b/include/linux/i2c.h
@@ -338,8 +338,7 @@
void *algo_data;
/* data fields that are valid for all devices */
- u8 level; /* nesting level for lockdep */
- struct mutex bus_lock;
+ struct rt_mutex bus_lock;
int timeout; /* in jiffies */
int retries;
@@ -367,7 +366,7 @@
*/
static inline void i2c_lock_adapter(struct i2c_adapter *adapter)
{
- mutex_lock(&adapter->bus_lock);
+ rt_mutex_lock(&adapter->bus_lock);
}
/**
@@ -376,7 +375,7 @@
*/
static inline void i2c_unlock_adapter(struct i2c_adapter *adapter)
{
- mutex_unlock(&adapter->bus_lock);
+ rt_mutex_unlock(&adapter->bus_lock);
}
/*flags for the client struct: */
