2bc9cd66eb
If an IIO driver uses callbacks from another IIO driver and calls
iio_channel_start_all_cb() from one of its buffer setup ops, then
lockdep complains due to the lock nesting, as in the below example with
lmp91000.
Since the locks are being taken on different IIO devices, there is no
actual deadlock. Fix the warning by telling lockdep to use a different
class for each iio_device.
============================================
WARNING: possible recursive locking detected
--------------------------------------------
python3/23 is trying to acquire lock:
(&indio_dev->mlock){+.+.}-{3:3}, at: iio_update_buffers
but task is already holding lock:
(&indio_dev->mlock){+.+.}-{3:3}, at: enable_store
other info that might help us debug this:
Possible unsafe locking scenario:
CPU0
----
lock(&indio_dev->mlock);
lock(&indio_dev->mlock);
*** DEADLOCK ***
May be due to missing lock nesting notation
5 locks held by python3/23:
#0: (sb_writers#5){.+.+}-{0:0}, at: ksys_write
#1: (&of->mutex){+.+.}-{3:3}, at: kernfs_fop_write_iter
#2: (kn->active#14){.+.+}-{0:0}, at: kernfs_fop_write_iter
#3: (&indio_dev->mlock){+.+.}-{3:3}, at: enable_store
#4: (&iio_dev_opaque->info_exist_lock){+.+.}-{3:3}, at: iio_update_buffers
Call Trace:
__mutex_lock
iio_update_buffers
iio_channel_start_all_cb
lmp91000_buffer_postenable
__iio_update_buffers
enable_store
Fixes: 67e17300dc1d76 ("iio: potentiostat: add LMP91000 support")
Signed-off-by: Vincent Whitchurch <vincent.whitchurch@axis.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Link: https://lore.kernel.org/r/20220829091840.2791846-1-vincent.whitchurch@axis.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.