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Found using DEBUG_ATOMIC_SLEEP while submitting an AIO read operation: [ 100.853642] BUG: sleeping function called from invalid context at mm/slab.h:421 [ 100.861148] in_atomic(): 1, irqs_disabled(): 1, pid: 1880, name: python [ 100.867954] 2 locks held by python/1880: [ 100.867961] #0: (&epfile->mutex){....}, at: [<f8188627>] ffs_mutex_lock+0x27/0x30 [usb_f_fs] [ 100.868020] #1: (&(&ffs->eps_lock)->rlock){....}, at: [<f818ad4b>] ffs_epfile_io.isra.17+0x24b/0x590 [usb_f_fs] [ 100.868076] CPU: 1 PID: 1880 Comm: python Not tainted 4.14.0-edison+ #118 [ 100.868085] Hardware name: Intel Corporation Merrifield/BODEGA BAY, BIOS 542 2015.01.21:18.19.48 [ 100.868093] Call Trace: [ 100.868122] dump_stack+0x47/0x62 [ 100.868156] ___might_sleep+0xfd/0x110 [ 100.868182] __might_sleep+0x68/0x70 [ 100.868217] kmem_cache_alloc_trace+0x4b/0x200 [ 100.868248] ? dwc3_gadget_ep_alloc_request+0x24/0xe0 [dwc3] [ 100.868302] dwc3_gadget_ep_alloc_request+0x24/0xe0 [dwc3] [ 100.868343] usb_ep_alloc_request+0x16/0xc0 [udc_core] [ 100.868386] ffs_epfile_io.isra.17+0x444/0x590 [usb_f_fs] [ 100.868424] ? _raw_spin_unlock_irqrestore+0x27/0x40 [ 100.868457] ? kiocb_set_cancel_fn+0x57/0x60 [ 100.868477] ? ffs_ep0_poll+0xc0/0xc0 [usb_f_fs] [ 100.868512] ffs_epfile_read_iter+0xfe/0x157 [usb_f_fs] [ 100.868551] ? security_file_permission+0x9c/0xd0 [ 100.868587] ? rw_verify_area+0xac/0x120 [ 100.868633] aio_read+0x9d/0x100 [ 100.868692] ? __fget+0xa2/0xd0 [ 100.868727] ? __might_sleep+0x68/0x70 [ 100.868763] SyS_io_submit+0x471/0x680 [ 100.868878] do_int80_syscall_32+0x4e/0xd0 [ 100.868921] entry_INT80_32+0x2a/0x2a [ 100.868932] EIP: 0xb7fbb676 [ 100.868941] EFLAGS: 00000292 CPU: 1 [ 100.868951] EAX: ffffffda EBX: b7aa2000 ECX: 00000002 EDX: b7af8368 [ 100.868961] ESI: b7fbb660 EDI: b7aab000 EBP: bfb6c658 ESP: bfb6c638 [ 100.868973] DS: 007b ES: 007b FS: 0000 GS: 0033 SS: 007b Signed-off-by: Vincent Pelletier <plr.vincent@gmail.com> Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>
To understand all the Linux-USB framework, you'll use these resources:
* This source code. This is necessarily an evolving work, and
includes kerneldoc that should help you get a current overview.
("make pdfdocs", and then look at "usb.pdf" for host side and
"gadget.pdf" for peripheral side.) Also, Documentation/usb has
more information.
* The USB 2.0 specification (from www.usb.org), with supplements
such as those for USB OTG and the various device classes.
The USB specification has a good overview chapter, and USB
peripherals conform to the widely known "Chapter 9".
* Chip specifications for USB controllers. Examples include
host controllers (on PCs, servers, and more); peripheral
controllers (in devices with Linux firmware, like printers or
cell phones); and hard-wired peripherals like Ethernet adapters.
* Specifications for other protocols implemented by USB peripheral
functions. Some are vendor-specific; others are vendor-neutral
but just standardized outside of the www.usb.org team.
Here is a list of what each subdirectory here is, and what is contained in
them.
core/ - This is for the core USB host code, including the
usbfs files and the hub class driver ("hub_wq").
host/ - This is for USB host controller drivers. This
includes UHCI, OHCI, EHCI, and others that might
be used with more specialized "embedded" systems.
gadget/ - This is for USB peripheral controller drivers and
the various gadget drivers which talk to them.
Individual USB driver directories. A new driver should be added to the
first subdirectory in the list below that it fits into.
image/ - This is for still image drivers, like scanners or
digital cameras.
../input/ - This is for any driver that uses the input subsystem,
like keyboard, mice, touchscreens, tablets, etc.
../media/ - This is for multimedia drivers, like video cameras,
radios, and any other drivers that talk to the v4l
subsystem.
../net/ - This is for network drivers.
serial/ - This is for USB to serial drivers.
storage/ - This is for USB mass-storage drivers.
class/ - This is for all USB device drivers that do not fit
into any of the above categories, and work for a range
of USB Class specified devices.
misc/ - This is for all USB device drivers that do not fit
into any of the above categories.