On Mon, Feb 22, 2016 at 1:17 AM, Wolfram Sang <wsa@xxxxxxxxxxxxx> wrote: > On Thu, Feb 18, 2016 at 05:53:05PM +0200, Daniel Baluta wrote: >> Sending this as an RFC because I don't know if style fixes are appropriate >> for this driver and also not sure if deadlock fix is the best solution. >> >> I2C people should only look at patches 8/9 and 9/9. >> >> The mpu6050 accel+gyro combo has an auxiliary I2C bus, allowing for >> an auxiliary sensor to be connected (eg. a magnetometer). >> >> The mpu can either act as an I2C master (functionality not currently >> implemented in the driver) or it can use a bypass multiplexer which >> directly connects the auxiliary I2C bus pins to the main I2C bus pins [1] >> Currently the driver implements the bypass mode via an I2C mux. >> >> This patchset fixes a deadlock in inv-mpu6050 IMU which happens when >> magnetometer (on auxiliary I2C bus) runs in parallel with accel or gyro. >> >> First 7 patches do some cleanup in order to make INV MPU6050 code easier >> to read. >> >> Patch number 8 allows passing NULL select callbacks to i2c_mux_master_xfer >> and i2c_mux_smbus_xfer. >> >> Patch number 9 actually fixes the deadlock. > > We recently had a bigger patch series fixing locking problems related to > muxes. I sadly didn't have the time to review it. Can you have a look if > it helps your case? > > http://thread.gmane.org/gmane.linux.drivers.i2c/26169 Hi Wolfram, Tested this and the deadlock is still there :(. It can be easily reproduced with following patch which enlarges the race window: iff --git a/drivers/iio/imu/inv_mpu6050/inv_mpu_core.c b/drivers/iio/imu/inv_mpu6050/inv_mpu_core.c index a3f5070..279d6e0 100644 --- a/drivers/iio/imu/inv_mpu6050/inv_mpu_core.c +++ b/drivers/iio/imu/inv_mpu6050/inv_mpu_core.c @@ -232,6 +232,7 @@ inv_mpu6050_read_raw(struct iio_dev *indio_dev, ret = IIO_VAL_INT; result = 0; mutex_lock(&indio_dev->mlock); + msleep(12000); if (!st->chip_config.enable) { result = inv_mpu6050_set_power_itg(st, true); if (result) using the following commands: $ cat /sys/bus/iio/devices/iio:device0/in_accel_x_raw $ cat /sys/bus/iio/devices/iio:device1/in_magn_x_raw Off topic: I'm very curious why I didn't get a lockdep splat while running this, might be because adapter lock is a rt_mutex. thanks, Daniel. -- To unsubscribe from this list: send the line "unsubscribe linux-iio" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
