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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: 67e17300dc ("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>
81 lines
3.1 KiB
C
81 lines
3.1 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef _INDUSTRIAL_IO_OPAQUE_H_
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#define _INDUSTRIAL_IO_OPAQUE_H_
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/**
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* struct iio_dev_opaque - industrial I/O device opaque information
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* @indio_dev: public industrial I/O device information
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* @id: used to identify device internally
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* @currentmode: operating mode currently in use, may be eventually
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* checked by device drivers but should be considered
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* read-only as this is a core internal bit
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* @driver_module: used to make it harder to undercut users
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* @mlock_key: lockdep class for iio_dev lock
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* @info_exist_lock: lock to prevent use during removal
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* @trig_readonly: mark the current trigger immutable
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* @event_interface: event chrdevs associated with interrupt lines
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* @attached_buffers: array of buffers statically attached by the driver
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* @attached_buffers_cnt: number of buffers in the array of statically attached buffers
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* @buffer_ioctl_handler: ioctl() handler for this IIO device's buffer interface
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* @buffer_list: list of all buffers currently attached
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* @channel_attr_list: keep track of automatically created channel
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* attributes
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* @chan_attr_group: group for all attrs in base directory
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* @ioctl_handlers: ioctl handlers registered with the core handler
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* @groups: attribute groups
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* @groupcounter: index of next attribute group
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* @legacy_scan_el_group: attribute group for legacy scan elements attribute group
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* @legacy_buffer_group: attribute group for legacy buffer attributes group
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* @bounce_buffer: for devices that call iio_push_to_buffers_with_timestamp_unaligned()
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* @bounce_buffer_size: size of currently allocate bounce buffer
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* @scan_index_timestamp: cache of the index to the timestamp
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* @clock_id: timestamping clock posix identifier
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* @chrdev: associated character device
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* @flags: file ops related flags including busy flag.
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* @debugfs_dentry: device specific debugfs dentry
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* @cached_reg_addr: cached register address for debugfs reads
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* @read_buf: read buffer to be used for the initial reg read
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* @read_buf_len: data length in @read_buf
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*/
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struct iio_dev_opaque {
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struct iio_dev indio_dev;
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int currentmode;
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int id;
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struct module *driver_module;
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struct lock_class_key mlock_key;
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struct mutex info_exist_lock;
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bool trig_readonly;
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struct iio_event_interface *event_interface;
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struct iio_buffer **attached_buffers;
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unsigned int attached_buffers_cnt;
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struct iio_ioctl_handler *buffer_ioctl_handler;
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struct list_head buffer_list;
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struct list_head channel_attr_list;
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struct attribute_group chan_attr_group;
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struct list_head ioctl_handlers;
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const struct attribute_group **groups;
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int groupcounter;
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struct attribute_group legacy_scan_el_group;
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struct attribute_group legacy_buffer_group;
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void *bounce_buffer;
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size_t bounce_buffer_size;
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unsigned int scan_index_timestamp;
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clockid_t clock_id;
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struct cdev chrdev;
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unsigned long flags;
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#if defined(CONFIG_DEBUG_FS)
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struct dentry *debugfs_dentry;
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unsigned cached_reg_addr;
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char read_buf[20];
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unsigned int read_buf_len;
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#endif
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};
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#define to_iio_dev_opaque(_indio_dev) \
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container_of((_indio_dev), struct iio_dev_opaque, indio_dev)
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#endif
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