Low priority thread holding the i2c bus mutex could block
more high 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@xxxxxxxxx>
Signed-off-by: Mika Kuoppala <mika.kuoppala@xxxxxxxxx>
---
drivers/i2c/i2c-core.c | 12 ++++++------
include/linux/i2c.h | 3 +--
2 files changed, 7 insertions(+), 8 deletions(-)
diff --git a/drivers/i2c/i2c-core.c b/drivers/i2c/i2c-core.c
index 0e45c29..40f645f 100644
--- a/drivers/i2c/i2c-core.c
+++ b/drivers/i2c/i2c-core.c
@@ -548,7 +548,7 @@ static int i2c_register_adapter(struct i2c_adapter *adap)
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)
@@ -1018,12 +1018,12 @@ int i2c_transfer(struct i2c_adapter *adap, struct i2c_msg *msgs, int num)
#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 */
@@ -1035,7 +1035,7 @@ int i2c_transfer(struct i2c_adapter *adap, struct i2c_msg *msgs, int num)
if (time_after(jiffies, orig_jiffies + adap->timeout))
break;
}
- mutex_unlock(&adap->bus_lock);
+ rt_mutex_unlock(&adap->bus_lock);
return ret;
} else {
@@ -1839,7 +1839,7 @@ s32 i2c_smbus_xfer(struct i2c_adapter *adapter, u16 addr, unsigned short flags,
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;
@@ -1853,7 +1853,7 @@ s32 i2c_smbus_xfer(struct i2c_adapter *adapter, u16 addr, unsigned short flags,
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 f4784c0..ddca85d 100644
--- a/include/linux/i2c.h
+++ b/include/linux/i2c.h
@@ -340,8 +340,7 @@ struct i2c_adapter {
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;
--
1.6.5.rc0
--
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