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It is not permitted to set task state before lock. usblp_wwait sets the state to TASK_INTERRUPTIBLE and calls mutex_lock_interruptible. Upon return from that function, the state will be TASK_RUNNING again. This is clearly a bug and a warning is generated with LOCKDEP too: WARNING: CPU: 1 PID: 5109 at kernel/sched/core.c:7404 __might_sleep+0x7d/0x90() do not call blocking ops when !TASK_RUNNING; state=1 set at [<ffffffffa0c588d0>] usblp_wwait+0xa0/0x310 [usblp] Modules linked in: ... CPU: 1 PID: 5109 Comm: captmon Tainted: G W 4.2.5-0.gef2823b-default #1 Hardware name: LENOVO 23252SG/23252SG, BIOS G2ET33WW (1.13 ) 07/24/2012 ffffffff81a4edce ffff880236ec7ba8 ffffffff81716651 0000000000000000 ffff880236ec7bf8 ffff880236ec7be8 ffffffff8106e146 0000000000000282 ffffffff81a50119 000000000000028b 0000000000000000 ffff8802dab7c508 Call Trace: ... [<ffffffff8106e1c6>] warn_slowpath_fmt+0x46/0x50 [<ffffffff8109a8bd>] __might_sleep+0x7d/0x90 [<ffffffff8171b20f>] mutex_lock_interruptible_nested+0x2f/0x4b0 [<ffffffffa0c588fc>] usblp_wwait+0xcc/0x310 [usblp] [<ffffffffa0c58bb2>] usblp_write+0x72/0x350 [usblp] [<ffffffff8121ed98>] __vfs_write+0x28/0xf0 ... Commit 7f477358e2384c54b190cc3b6ce28277050a041b (usblp: Implement the ENOSPC convention) moved the set prior locking. So move it back after the lock. Signed-off-by: Jiri Slaby <jslaby@suse.cz> Fixes: 7f477358e2 ("usblp: Implement the ENOSPC convention") Acked-By: Pete Zaitcev <zaitcev@yahoo.com> Cc: stable <stable@vger.kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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.