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[ Upstream commit54f64d5c98] Since the 5.0 merge window opened, I've been seeing frequent crashes on suspend and reboot with the trace: [ 36.911170] Unable to handle kernel paging request at virtual address ffffff801153d660 [ 36.912769] Unable to handle kernel paging request at virtual address ffffff800004b564 ... [ 36.950666] Call trace: [ 36.950670] queued_spin_lock_slowpath+0x1cc/0x2c8 [ 36.950681] _raw_spin_lock_irqsave+0x64/0x78 [ 36.950692] complete+0x28/0x70 [ 36.950703] ffs_epfile_io_complete+0x3c/0x50 [ 36.950713] usb_gadget_giveback_request+0x34/0x108 [ 36.950721] dwc3_gadget_giveback+0x50/0x68 [ 36.950723] dwc3_thread_interrupt+0x358/0x1488 [ 36.950731] irq_thread_fn+0x30/0x88 [ 36.950734] irq_thread+0x114/0x1b0 [ 36.950739] kthread+0x104/0x130 [ 36.950747] ret_from_fork+0x10/0x1c I isolated this down to in ffs_epfile_io(): https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/usb/gadget/function/f_fs.c#n1065 Where the completion done is setup on the stack: DECLARE_COMPLETION_ONSTACK(done); Then later we setup a request and queue it, and wait for it: if (unlikely(wait_for_completion_interruptible(&done))) { /* * To avoid race condition with ffs_epfile_io_complete, * dequeue the request first then check * status. usb_ep_dequeue API should guarantee no race * condition with req->complete callback. */ usb_ep_dequeue(ep->ep, req); interrupted = ep->status < 0; } The problem is, that we end up being interrupted, dequeue the request, and exit. But then the irq triggers and we try calling complete() on the context pointer which points to now random stack space, which results in the panic. Alan Stern pointed out there is a bug here, in that the snippet above "assumes that usb_ep_dequeue() waits until the request has been completed." And that: wait_for_completion(&done); Is needed right after the usb_ep_dequeue(). Thus this patch implements that change. With it I no longer see the crashes on suspend or reboot. This issue seems to have been uncovered by behavioral changes in the dwc3 driver in commitfec9095bde("usb: dwc3: gadget: remove wait_end_transfer"). Cc: Alan Stern <stern@rowland.harvard.edu> Cc: Felipe Balbi <balbi@kernel.org> Cc: Zeng Tao <prime.zeng@hisilicon.com> Cc: Jack Pham <jackp@codeaurora.org> Cc: Thinh Nguyen <thinh.nguyen@synopsys.com> Cc: Chen Yu <chenyu56@huawei.com> Cc: Jerry Zhang <zhangjerry@google.com> Cc: Lars-Peter Clausen <lars@metafoo.de> Cc: Vincent Pelletier <plr.vincent@gmail.com> Cc: Andrzej Pietrasiewicz <andrzej.p@samsung.com> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: Linux USB List <linux-usb@vger.kernel.org> Suggested-by: Alan Stern <stern@rowland.harvard.edu> Signed-off-by: John Stultz <john.stultz@linaro.org> Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com> Signed-off-by: Sasha Levin <sashal@kernel.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.